UNISON(1) ========= NAME ---- unison - File Synchronizer SYNOPSIS -------- unison [options] unison root1 root2 [options] unison profilename [options] Description ----------- Unison is a file-synchronization tool for Unix and Windows. It allows two replicas of a collection of files and directories to be stored on different hosts (or different disks on the same host), modified separately, and then brought up to date by propagating the changes in each replica to the other. Preliminaries Unison can be used with either of two user interfaces: 1. a straightforward textual interface and 2. a more sophisticated graphical interface The textual interface is more convenient for running from scripts and works on dumb terminals; the graphical interface is better for most interactive use. For this tutorial, you can use either. If you are running Unison from the command line, just typing unison will select either the text or the graphical interface, depending on which has been selected as default when the executable you are running was built. You can force the text interface even if graphical is the default by adding -ui text. The other command-line arguments to both versions are identical. The graphical version can also be run directly by clicking on its icon, but this may require a little set-up (see the section "Click-starting Unison" ). For this tutorial, we assume that you're starting it from the command line. Unison can synchronize files and directories on a single machine, or between two machines on a network. (The same program runs on both machines; the only difference is which one is responsible for displaying the user interface.) If you're only interested in a single-machine setup, then let's call that machine the CLIENT . If you're synchronizing two machines, let's call them CLIENT and SERVER . Local Usage Let's get the client machine set up first and see how to synchronize two directories on a single machine. Follow the instructions in the section "Installation" to either download or build an executable version of Unison, and install it somewhere on your search path. (If you just want to use the textual user interface, download the appropriate textui binary. If you just want to the graphical interface--or if you will use both interfaces [the gtkui binary actually has both compiled in]--then download the gtkui binary.) Create a small test directory a.tmp containing a couple of files and/or subdirectories, e.g., mkdir a.tmp touch a.tmp/a a.tmp/b mkdir a.tmp/d touch a.tmp/d/f Copy this directory to b.tmp: cp -r a.tmp b.tmp Now try synchronizing a.tmp and b.tmp. (Since they are identical, synchronizing them won't propagate any changes, but Unison will remember the current state of both directories so that it will be able to tell next time what has changed.) Type: unison a.tmp b.tmp Textual Interface: * You should see a message notifying you that all the files are actually equal and then get returned to the command line. Graphical Interface: * You should get a big empty window with a message at the bottom notifying you that all files are identical. Choose the Exit item from the File menu to get back to the command line. Next, make some changes in a.tmp and/or b.tmp. For example: rm a.tmp/a echo "Hello" > a.tmp/b echo "Hello" > b.tmp/b date > b.tmp/c echo "Hi there" > a.tmp/d/h echo "Hello there" > b.tmp/d/h Run Unison again: unison a.tmp b.tmp This time, the user interface will display only the files that have changed. If a file has been modified in just one replica, then it will be displayed with an arrow indicating the direction that the change needs to be propagated. For example, <--- new file c [f] indicates that the file c has been modified only in the second replica, and that the default action is therefore to propagate the new version to the first replica. To follw Unison's recommendation, press the "f" at the prompt. If both replicas are modified and their contents are different, then the changes are in conflict: <-?-> is displayed to indicate that Unison needs guidance on which replica should override the other. new file <-?-> new file d/h [] By default, neither version will be propagated and both replicas will remain as they are. If both replicas have been modified but their new contents are the same (as with the file b), then no propagation is necessary and nothing is shown. Unison simply notes that the file is up to date. These display conventions are used by both versions of the user interface. The only difference lies in the way in which Unison's default actions are either accepted or overriden by the user. Textual Interface: * The status of each modified file is displayed, in turn. When the copies of a file in the two replicas are not identical, the user interface will ask for instructions as to how to propagate the change. If some default action is indicated (by an arrow), you can simply press Return to go on to the next changed file. If you want to do something different with this file, press "<" or ">" to force the change to be propagated from right to left or from left to right, or else press "/" to skip this file and leave both replicas alone. When it reaches the end of the list of modified files, Unison will ask you one more time whether it should proceed with the updates that have been selected. When Unison stops to wait for input from the user, pressing "?" will always give a list of possible responses and their meanings. Graphical Interface: * The main window shows all the files that have been modified in either a.tmp or b.tmp. To override a default action (or to select an action in the case when there is no default), first select the file, either by clicking on its name or by using the up- and down-arrow keys. Then press either the left-arrow or "<" key (to cause the version in b.tmp to propagate to a.tmp) or the right-arrow or ">" key (which makes the a.tmp version override b.tmp). Every keyboard command can also be invoked from the menus at the top of the user interface. (Conversely, each menu item is annotated with its keyboard equivalent, if it has one.) When you are satisfied with the directions for the propagation of changes as shown in the main window, click the "Go" button to set them in motion. A check sign will be displayed next to each filename when the file has been dealt with. Remote Usage Next, we'll get Unison set up to synchronize replicas on two different machines. Follow the instructions in the Installation section to download or build an executable version of Unison on the server machine, and install it somewhere on your search path. (It doesn't matter whether you install the textual or graphical version, since the copy of Unison on the server doesn't need to display any user interface at all.) It is important that the version of Unison installed on the server machine is the same as the version of Unison on the client machine. But some flexibility on the version of Unison at the client side can be achieved by using the -addversionno option; see the section "Preferences" . Now there is a decision to be made. Unison provides two methods for communicating between the client and the server: * Remote shell method: To use this method, you must have some way of invoking remote commands on the server from the client's command line, using a facility such as ssh. This method is more convenient (since there is no need to manually start a "unison server" process on the server) and also more secure (especially if you use ssh). * Socket method: This method requires only that you can get TCP packets from the client to the server and back. A draconian firewall can prevent this, but otherwise it should work anywhere. Decide which of these you want to try, and continue with the section "Remote Shell Method" or the section "Socket Method" , as appropriate. Remote Shell Method The standard remote shell facility on Unix systems is ssh, which provides the same functionality as the older rsh but much better security. Ssh is available from ftp://ftp.cs.hut.fi/pub/ssh/; up-to-date binaries for some architectures can also be found at ftp://ftp.faqs.org/ssh/contrib. See section [1]A.2 for installation instructions for the Windows version. Running ssh requires some coordination between the client and server machines to establish that the client is allowed to invoke commands on the server; please refer to the or ssh documentation for information on how to set this up. The examples in this section use ssh, but you can substitute rsh for ssh if you wish. First, test that we can invoke Unison on the server from the client. Typing ssh remotehostname unison -version should print the same version information as running unison -version locally on the client. If remote execution fails, then either something is wrong with your ssh setup (e.g., "permission denied") or else the search path that's being used when executing commands on the server doesn't contain the unison executable (e.g., "command not found"). Create a test directory a.tmp in your home directory on the client machine. Test that the local unison client can start and connect to the remote server. Type unison -testServer a.tmp ssh://remotehostname/a.tmp Now cd to your home directory and type: unison a.tmp ssh://remotehostname/a.tmp The result should be that the entire directory a.tmp is propagated from the client to your home directory on the server. After finishing the first synchronization, change a few files and try synchronizing again. You should see similar results as in the local case. If your user name on the server is not the same as on the client, you need to specify it on the command line: unison a.tmp ssh://username@remotehostname/a.tmp Notes: * If you want to put a.tmp some place other than your home directory on the remote host, you can give an absolute path for it by adding an extra slash between remotehostname and the beginning of the path: unison a.tmp ssh://remotehostname//absolute/path/to/a.tmp * You can give an explicit path for the unison executable on the server by using the command-line option "-servercmd /full/path/name/of/unison" or adding "servercmd=/full/path/name/of/unison" to your profile (see the section "Profile" ). Similarly, you can specify a explicit path for the ssh program using the "-sshcmd" option. Extra arguments can be passed to ssh by setting the -sshargs preference. Socket Method Warning: The socket method is insecure: not only are the texts of your changes transmitted over the network in unprotected form, it is also possible for anyone in the world to connect to the server process and read out the contents of your filesystem! (Of course, to do this they must understand the protocol that Unison uses to communicate between client and server, but all they need for this is a copy of the Unison sources.) The socket method is provided only for expert users with specific needs; everyone else should use the ssh method. To run Unison over a socket connection, you must start a Unison daemon process on the server. This process runs continuously, waiting for connections over a given socket from client machines running Unison and processing their requests in turn. To start the daemon, type unison -socket NNNN on the server machine, where NNNN is the socket number that the daemon should listen on for connections from clients. (NNNN can be any large number that is not being used by some other program; if NNNN is already in use, Unison will exit with an error message.) Note that paths specified by the client will be interpreted relative to the directory in which you start the server process; this behavior is different from the ssh case, where the path is relative to your home directory on the server. Create a test directory a.tmp in your home directory on the client machine. Now type: unison a.tmp socket://remotehostname:NNNN/a.tmp The result should be that the entire directory a.tmp is propagated from the client to the server (a.tmp will be created on the server in the directory that the server was started from). After finishing the first synchronization, change a few files and try synchronizing again. You should see similar results as in the local case. Since the socket method is not used by many people, its functionality is rather limited. For example, the server can only deal with one client at a time. Using Unison for All Your Files Once you are comfortable with the basic operation of Unison, you may find yourself wanting to use it regularly to synchronize your commonly used files. There are several possible ways of going about this: 1. Synchronize your whole home directory, using the Ignore facility (see the section "Ignore" ) to avoid synchronizing temporary files and things that only belong on one host. 2. Create a subdirectory called shared (or current, or whatever) in your home directory on each host, and put all the files you want to synchronize into this directory. 3. Create a subdirectory called shared (or current, or whatever) in your home directory on each host, and put links to all the files you want to synchronize into this directory. Use the follow preference (see the section "Symbolic Links" ) to make Unison treat these links as transparent. 4. Make your home directory the root of the synchronization, but tell Unison to synchronize only some of the files and subdirectories within it on any given run. This can be accomplished by using the -path switch on the command line: unison /home/username ssh://remotehost//home/username -path shared The -path option can be used as many times as needed, to synchronize several files or subdirectories: unison /home/username ssh://remotehost//home/username \ -path shared \ -path pub \ -path .netscape/bookmarks.html These -path arguments can also be put in your preference file. See the section "Preferences" for an example. Most people find that they only need to maintain a profile (or profiles) on one of the hosts that they synchronize, since Unison is always initiated from this host. (For example, if you're synchronizing a laptop with a fileserver, you'll probably always run Unison on the laptop.) This is a bit different from the usual situation with asymmetric mirroring programs like rdist, where the mirroring operation typically needs to be initiated from the machine with the most recent changes. the section "Profile" covers the syntax of Unison profiles, together with some sample profiles. Some tips on improving Unison's performance can be found on the Frequently Asked Questions page (http://www.cis.upenn.edu/~bcpierce/unison/faq.html). Using Unison to Synchronize More Than Two Machines Unison is designed for synchronizing pairs of replicas. However, it is possible to use it to keep larger groups of machines in sync by performing multiple pairwise synchronizations. If you need to do this, the most reliable way to set things up is to organize the machines into a "star topology," with one machine designated as the "hub" and the rest as "spokes," and with each spoke machine synchronizing only with the hub. The big advantage of the star topology is that it eliminates the possibility of confusing "spurious conflicts" arising from the fact that a separate archive is maintained by Unison for every pair of hosts that it synchronizes. Going Further On-line documentation for the various features of Unison can be obtained either by typing unison -doc topics at the command line, or by selecting the Help menu in the graphical user interface. The same information is also available in a typeset User's Manual (HTML or PostScript format) through http://www.cis.upenn.edu/~bcpierce/unison. If you use Unison regularly, you should subscribe to one of the mailing lists, to receive announcements of new versions. See the section "Mailing Lists" . Basic Concepts To understand how Unison works, it is necessary to discuss a few straightforward concepts. These concepts are developed more rigorously and at more length in a number of papers, available at http://www.cis.upenn.edu/~bcpierce/papers. But the informal presentation here should be enough for most users. Roots A replica's root tells Unison where to find a set of files to be synchronized, either on the local machine or on a remote host. For example, relative/path/of/root specifies a local root relative to the directory where Unison is started, while /absolute/path/of/root specifies a root relative to the top of the local filesystem, independent of where Unison is running. Remote roots can begin with ssh://, rsh:// to indicate that the remote server should be started with rsh or ssh: ssh://remotehost//absolute/path/of/root rsh://user@remotehost/relative/path/of/root If the remote server is already running (in the socket mode), then the syntax socket://remotehost:portnum//absolute/path/of/root socket://remotehost:portnum/relative/path/of/root is used to specify the hostname and the port that the client Unison should use to contact it. The syntax for roots is based on that of URIs (described in RFC 2396). The full grammar is: replica ::= [protocol:]//[user@][host][:port][/path] | path protocol ::= file | socket | ssh | rsh user ::= [-_a-zA-Z0-9]+ host ::= [-_a-zA-Z0-9.]+ port ::= [0-9]+ When path is given without any protocol prefix, the protocol is assumed to be file:. Under Windows, it is possible to synchronize with a remote directory using the file: protocol over the Windows Network Neighborhood. For example, unison foo //host/drive/bar synchronizes the local directory foo with the directory drive:\bar on the machine host, provided that host is accessible via Network Neighborhood. When the file: protocol is used in this way, there is no need for a Unison server to be running on the remote host. However, running Unison this way is only a good idea if the remote host is reached by a very fast network connection, since the full contents of every file in the remote replica will have to be transferred to the local machine to detect updates. The names of roots are canonized by Unison before it uses them to compute the names of the corresponding archive files, so //saul//home/bcpierce/common and //saul.cis.upenn.edu/common will be recognized as the same replica under different names. Paths A path refers to a point within a set of files being synchronized; it is specified relative to the root of the replica. Formally, a path is just a sequence of names, separated by /. Note that the path separator character is always a forward slash, no matter what operating system Unison is running on. Forward slashes are converted to backslashes as necessary when paths are converted to filenames in the local filesystem on a particular host. (For example, suppose that we run Unison on a Windows system, synchronizing the local root c:\pierce with the root ssh://saul.cis.upenn.edu/home/bcpierce on a Unix server. Then the path current/todo.txt refers to the file c:\pierce\current\todo.txt on the client and /home/bcpierce/current/todo.txt on the server.) The empty path (i.e., the empty sequence of names) denotes the whole replica. Unison displays the empty path as "[root]." If p is a path and q is a path beginning with p, then q is said to be a descendant of p. (Each path is also a descendant of itself.) What is an Update? The contents of a path p in a particular replica could be a file, a directory, a symbolic link, or absent (if p does not refer to anything at all in that replica). More specifically: * If p refers to an ordinary file, then the contents of p are the actual contents of this file (a string of bytes) plus the current permission bits of the file. * If p refers to a symbolic link, then the contents of p are just the string specifying where the link points. * If p refers to a directory, then the contents of p are just the token "DIRECTORY" plus the current permission bits of the directory. * If p does not refer to anything in this replica, then the contents of p are the token "ABSENT." Unison keeps a record of the contents of each path after each successful synchronization of that path (i.e., it remembers the contents at the last moment when they were the same in the two replicas). We say that a path is updated (in some replica) if its current contents are different from its contents the last time it was successfully synchronized. Note that whether a path is updated has nothing to do with its last modification time--Unison considers only the contents when determining whether an update has occurred. This means that touching a file without changing its contents will not be recognized as an update. A file can even be changed several times and then changed back to its original contents; as long as Unison is only run at the end of this process, no update will be recognized. What Unison actually calculates is a close approximation to this definition; see the section "Caveats and Shortcomings" . What is a Conflict? A path is said to be conflicting if the following conditions all hold: 1. it has been updated in one replica, 2. it or any of its descendants has been updated in the other replica, and 3. its contents in the two replicas are not identical. Reconciliation Unison operates in several distinct stages: 1. On each host, it compares its archive file (which records the state of each path in the replica when it was last synchronized) with the current contents of the replica, to determine which paths have been updated. 2. It checks for "false conflicts" -- paths that have been updated on both replicas, but whose current values are identical. These paths are silently marked as synchronized in the archive files in both replicas. 3. It displays all the updated paths to the user. For updates that do not conflict, it suggests a default action (propagating the new contents from the updated replica to the other). Conflicting updates are just displayed. The user is given an opportunity to examine the current state of affairs, change the default actions for nonconflicting updates, and choose actions for conflicting updates. 4. It performs the selected actions, one at a time. Each action is performed by first transferring the new contents to a temporary file on the receiving host, then atomically moving them into place. 5. It updates its archive files to reflect the new state of the replicas. Invariants Given the importance and delicacy of the job that it performs, it is important to understand both what a synchronizer does under normal conditions and what can happen under unusual conditions such as system crashes and communication failures. Unison is careful to protect both its internal state and the state of the replicas at every point in this process. Specifically, the following guarantees are enforced: * At every moment, each path in each replica has either (1) its original contents (i.e., no change at all has been made to this path), or (2) its correct final contents (i.e., the value that the user expected to be propagated from the other replica). * At every moment, the information stored on disk about Unison's private state can be either (1) unchanged, or (2) updated to reflect those paths that have been successfully synchronized. The upshot is that it is safe to interrupt Unison at any time, either manually or accidentally. [Caveat: the above is almost true there are occasionally brief periods where it is not (and, because of shortcoming of the Posix filesystem API, cannot be); in particular, when it is copying a file onto a directory or vice versa, it must first move the original contents out of the way. If Unison gets interrupted during one of these periods, some manual cleanup may be required. In this case, a file called DANGER.README will be left in your home directory, containing information about the operation that was interrupted. The next time you try to run Unison, it will notice this file and warn you about it.] If an interruption happens while it is propagating updates, then there may be some paths for which an update has been propagated but which have not been marked as synchronized in Unison's archives. This is no problem: the next time Unison runs, it will detect changes to these paths in both replicas, notice that the contents are now equal, and mark the paths as successfully updated when it writes back its private state at the end of this run. If Unison is interrupted, it may sometimes leave temporary working files (with suffix .tmp) in the replicas. It is safe to delete these files. Also, if the backups flag is set, Unison will leave around old versions of files that it overwrites, with names like file.0.unison.bak. These can be deleted safely when they are no longer wanted. Unison is not bothered by clock skew between the different hosts on which it is running. It only performs comparisons between timestamps obtained from the same host, and the only assumption it makes about them is that the clock on each system always runs forward. If Unison finds that its archive files have been deleted (or that the archive format has changed and they cannot be read, or that they don't exist because this is the first run of Unison on these particular roots), it takes a conservative approach: it behaves as though the replicas had both been completely empty at the point of the last synchronization. The effect of this is that, on the first run, files that exist in only one replica will be propagated to the other, while files that exist in both replicas but are unequal will be marked as conflicting. Touching a file without changing its contents should never affect whether or not Unison does an update. (When running with the fastcheck preference set to true--the default on Unix systems--Unison uses file modtimes for a quick first pass to tell which files have definitely not changed; then, for each file that might have changed, it computes a fingerprint of the file's contents and compares it against the last-synchronized contents. Also, the -times option allows you to synchronize file times, but it does not cause identical files to be changed; Unison will only modify the file times.) It is safe to "brainwash" Unison by deleting its archive files on both replicas. The next time it runs, it will assume that all the files it sees in the replicas are new. It is safe to modify files while Unison is working. If Unison discovers that it has propagated an out-of-date change, or that the file it is updating has changed on the target replica, it will signal a failure for that file. Run Unison again to propagate the latest change. Changes to the ignore patterns from the user interface (e.g., using the `i' key) are immediately reflected in the current profile. Caveats and Shortcomings Here are some things to be careful of when using Unison. * In the interests of speed, the update detection algorithm may (depending on which OS architecture that you run Unison on) actually use an approximation to the definition given in the section "What is an Update?" . In particular, the Unix implementation does not compare the actual contents of files to their previous contents, but simply looks at each file's inode number and modtime; if neither of these have changed, then it concludes that the file has not been changed. Under normal circumstances, this approximation is safe, in the sense that it may sometimes detect "false updates" will never miss a real one. However, it is possible to fool it, for example by using retouch to change a file's modtime back to a time in the past. * If you synchronize between a single-user filesystem and a shared Unix server, you should pay attention to your permission bits: by default, Unison will synchronize permissions verbatim, which may leave group-writable files on the server that could be written over by a lot of people. You can control this by setting your umask on both computers to something like 022, masking out the "world write" and "group write" permission bits. Unison does not synchronize the setuid and setgid bits, for security. * The graphical user interface is single-threaded. This means that if Unison is performing some long-running operation, the display will not be repainted until it finishes. We recommend not trying to do anything with the user interface while Unison is in the middle of detecting changes or propagating files. * Unison does not understand hard links. * Unison does not support synchronization of ACL and extended file attributes. * It is important to be a little careful when renaming directories containing "ignore"d files. For example, suppose Unison is synchronizing directory A between the two machines called the "local" and the "remote" machine; suppose directory A contains a subdirectory D; and suppose D on the local machine contains a file or subdirectory P that matches an ignore directive in the profile used to synchronize. Thus path A/D/P exists on the local machine but not on the remote machine. If D is renamed to D' on the remote machine, and this change is propagated to the local machine, all such files or subdirectories P will be deleted. This is because Unison sees the rename as a delete and a separate create: it deletes the old directory (including the ignored files) and creates a new one (not including the ignored files, since they are completely invisible to it). Running Unison There are several ways to start Unison. * Typing "unison profile" on the command line. Unison will look for a file profile.prf in the .unison directory. If this file does not specify a pair of roots, Unison will prompt for them and add them to the information specified by the profile. * Typing "unison profile root1 root2" on the command line. In this case, Unison will use profile, which should not contain any root directives. * Typing "unison root1 root2" on the command line. This has the same effect as typing "unison default root1 root2." * Typing just "unison" (or invoking Unison by clicking on a desktop icon). In this case, Unison will ask for the profile to use for synchronization (or create a new one, if necessary). The .unison Directory Unison stores a variety of information in a private directory on each host. If the environment variable UNISON is defined, then its value will be used as the name of this directory. If UNISON is not defined, then the name of the directory depends on which operating system you are using. In Unix, the default is to use $HOME/.unison. In Windows, if the environment variable USERPROFILE is defined, then the directory will be $USERPROFILE\.unison; otherwise if HOME is defined, it will be $HOME\.unison; otherwise, it will be c:\.unison. The archive file for each replica is found in the .unison directory on that replica's host. Profiles (described below) are always taken from the .unison directory on the client host. Note that Unison maintains a completely different set of archive files for each pair of roots. We do not recommend synchronizing the whole .unison directory, as this will involve frequent propagation of large archive files. It should be safe to do it, though, if you really want to. Synchronizing just the profile files in the .unison directory is definitely OK. Archive Files The name of the archive file on each replica is calculated from * the canonical names of all the hosts (short names like saul are converted into full addresses like saul.cis.upenn.edu), * the paths to the replicas on all the hosts (again, relative pathnames, symbolic links, etc. are converted into full, absolute paths), and * an internal version number that is changed whenever a new Unison release changes the format of the information stored in the archive. This method should work well for most users. However, it is occasionally useful to change the way archive names are generated. Unison provides two ways of doing this. The function that finds the canonical hostname of the local host (which is used, for example, in calculating the name of the archive file used to remember which files have been synchronized) normally uses the gethostname operating system call. However, if the environment variable UNISONLOCALHOSTNAME is set, its value will be used instead. This makes it easier to use Unison in situations where a machine's name changes frequently (e.g., because it is a laptop and gets moved around a lot). A more powerful way of changing archive names is provided by the rootalias preference. The preference file may contain any number of lines of the form: rootalias = //hostnameA//path-to-replicaA -> //hostnameB//path-to-replicaB When calculating the name of the archive files for a given pair of roots, Unison replaces any root that matches the left-hand side of any rootalias rule by the corresponding right-hand side. So, if you need to relocate a root on one of the hosts, you can add a rule of the form: rootalias = //new-hostname//new-path -> //old-hostname//old-path Warning: The rootalias option is dangerous and should only be used if you are sure you know what you're doing. In particular, it should only be used if you are positive that either (1) both the original root and the new alias refer to the same set of files, or (2) the files have been relocated so that the original name is now invalid and will never be used again. (If the original root and the alias refer to different sets of files, Unison's update detector could get confused.) After introducing a new rootalias, it is a good idea to run Unison a few times interactively (with the batch flag off, etc.) and carefully check that things look reasonable--in particular, that update detection is working as expected. Preferences Many details of Unison's behavior are configurable by user-settable "preferences." Some preferences are boolean-valued; these are often called flags. Others take numeric or string arguments, indicated in the preferences list by n or xxx. Most of the string preferences can be given several times; the arguments are accumulated into a list internally. There are two ways to set the values of preferences: temporarily, by providing command-line arguments to a particular run of Unison, or permanently, by adding commands to a profile in the .unison directory on the client host. The order of preferences (either on the command line or in preference files) is not significant. On the command line, preferences and other arguments (the profile name and roots) can be intermixed in any order. To set the value of a preference p from the command line, add an argument -p (for a boolean flag) or -p n or -p xxx (for a numeric or string preference) anywhere on the command line. To set a boolean flag to false on the command line, use -p=false. Here are all the preferences supported by Unison. This list can be obtained by typing unison -help. Usage: unison [options] ----------------------- or unison root1 root2 [options] or unison profilename [options] Options: -------- -addprefsto xxx file to add new prefs to -addversionno add version number to name of unison executable on server -auto automatically accept default actions -backup xxx add a pattern to the backup list -backupcurrent xxx add a pattern to the backupcurrent list -backupcurrentnot xxx add a pattern to the backupcurrentnot list -backupdir xxx Directory for storing centralized backups -backuplocation xxx where backups are stored ('local' or 'central') -backupnot xxx add a pattern to the backupnot list -backupprefix xxx prefix for the names of backup files -backups keep backup copies of all files (see also 'backup') -backupsuffix xxx a suffix to be added to names of backup files -batch batch mode: ask no questions at all -confirmbigdeletes request confirmation for whole-replica deletes -confirmmerge ask for confirmation before commiting results of a merge -contactquietly Suppress the 'contacting server' message during startup -debug xxx debug module xxx ('all' -> everything, 'verbose' -> more) -doc xxx show documentation ('-doc topics' lists topics) -dumbtty do not try to change terminal settings in text UI -fastcheck xxx do fast update detection (`true', `false', or `default') -follow xxx add a pattern to the follow list -force xxx force changes from this replica to the other -forcepartial xxx add a pattern to the forcepartial list -group synchronize group -height n height (in lines) of main window in graphical interface -host xxx bind the socket to this host name in server socket mode -ignore xxx add a pattern to the ignore list -ignorecase xxx ignore upper/lowercase in filenames (`true', `false', or `default') -ignorelocks ignore locks left over from previous run (dangerous!) -ignorenot xxx add a pattern to the ignorenot list -immutable xxx add a pattern to the immutable list -immutablenot xxx add a pattern to the immutablenot list -key xxx define a keyboard shortcut for this profile (in some UIs) -killserver kill server when done (even when using sockets) -label xxx provide a descriptive string label for this profile -log record actions in file specified by logfile preference -logfile xxx Log file name -maxbackups n number of backed up versions of a file -maxthreads n maximum number of simultaneous file transfers -merge xxx add a pattern to the merge list -mountpoint xxx abort if this path does not exist -numericids don't map uid/gid values by user/group names -owner synchronize owner -path xxx path to synchronize -perms n part of the permissions which is synchronized -prefer xxx choose this replica's version for conflicting changes -preferpartial xxx add a pattern to the preferpartial list -pretendwin Use creation times for detecting updates -repeat xxx synchronize repeatedly (text interface only) -retry n re-try failed synchronizations N times (text interface on ly) -root xxx root of a replica -rootalias xxx Register alias for canonical root names -rsrc xxx synchronize resource forks and HFS meta-data (`true', `fa lse', or `default') -rsync activate the rsync transfer mode -selftest run internal tests and exit -servercmd xxx name of unison executable on remote server -showarchive show name of archive and 'true names' (for rootalias) of roots -silent print nothing (except error messages) -socket xxx act as a server on a socket -sortbysize list changed files by size, not name -sortfirst xxx add a pattern to the sortfirst list -sortlast xxx add a pattern to the sortlast list -sortnewfirst list new before changed files -sshargs xxx other arguments (if any) for remote shell command -sshcmd xxx path to the ssh executable -terse suppress status messages -testserver exit immediately after the connection to the server -times synchronize modification times -ui xxx select user interface ('text' or 'graphic'); command-line only -version print version and exit -xferbycopying optimize transfers using local copies, if possible Here, in more detail, are what they do. Many are discussed in even greater detail in other sections of the manual. addprefsto xxx By default, new preferences added by Unison (e.g., new ignore clauses) will be appended to whatever preference file Unison was told to load at the beginning of the run. Setting the preference addprefsto filename makes Unison add new preferences to the file named filename instead. addversionno When this flag is set to true, Unison will use unison-currentversionnumber instead of just unison as the remote server command. This allows multiple binaries for different versions of unison to coexist conveniently on the same server: whichever version is run on the client, the same version will be selected on the server. auto When set to true, this flag causes the user interface to skip asking for confirmations on non-conflicting changes. (More precisely, when the user interface is done setting the propagation direction for one entry and is about to move to the next, it will skip over all non-conflicting entries and go directly to the next conflict.) backup xxx Including the preference -backup pathspec causes Unison to keep backup files for each path that matches pathspec. These backup files are kept in the directory specified by the backuplocation preference. The backups are named according to the backupprefix and backupsuffix preferences. The number of versions that are kept is determined by the maxbackups preference. The syntax of pathspec is described in the section "Path Specification" . backupcurrent xxx Including the preference -backupcurrent pathspec causes Unison to keep a backup of the current version of every file matching pathspec. This file will be saved as a backup with version number 000. Such backups can be used as inputs to external merging programs, for instance. See the documentatation for the merge preference. For more details, see the section "Merging Conflicting Versions" . The syntax of pathspec is described in the section "Path Specification" . backupcurrentnot xxx Exceptions to backupcurrent, like the ignorenot preference. backupdir xxx If this preference is set, Unison will use it as the name of the directory used to store backup files specified by the backup preference, when backuplocation is set to central. It is checked after the UNISONBACKUPDIR environment variable. backuplocation xxx This preference determines whether backups should be kept locally, near the original files, or in a central directory specified by the backupdir preference. If set to local, backups will be kept in the same directory as the original files, and if set to central, backupdir will be used instead. backupnot xxx The values of this preference specify paths or individual files or regular expressions that should not be backed up, even if the backup preference selects them--i.e., it selectively overrides backup. The same caveats apply here as with ignore and t ignorenot. backupprefix xxx When a backup for a file NAME is created, it is stored in a directory specified by backuplocation, in a file called backupprefixNAMEbackupsuffix. backupprefix can include a directory name (causing Unison to keep all backup files for a given directory in a subdirectory with this name), and both backupprefix and backupsuffix can contain the string$VERSION, which will be replaced by the age of the backup (1 for the most recent, 2 for the second most recent, and so on...). This keyword is ignored if it appears in a directory name in the prefix; if it does not appear anywhere in the prefix or the suffix, it will be automatically placed at the beginning of the suffix. backups Setting this flag to true is equivalent to setting backuplocation to local and backup to Name *. backupsuffix xxx See backupprefix for full documentation. batch When this is set to true, the user interface will ask no questions at all. Non-conflicting changes will be propagated; conflicts will be skipped. confirmbigdeletes When this is set to true, Unison will request an extra confirmation if it appears that the entire replica has been deleted, before propagating the change. If the batch flag is also set, synchronization will be aborted. When the path preference is used, the same confirmation will be requested for top-level paths. (At the moment, this flag only affects the text user interface.) See also the mountpoint preference. confirmmerge Setting this preference causes both the text and graphical interfaces to ask the user if the results of a merge command may be commited to the replica or not. Since the merge command works on temporary files, the user can then cancel all the effects of applying the merge if it turns out that the result is not satisfactory. In batch-mode, this preference has no effect. contactquietly If this flag is set, Unison will skip displaying the `Contacting server' message (which some users find annoying) during startup. debug xxx This preference is used to make Unison print various sorts of information about what it is doing internally on the standard error stream. It can be used many times, each time with the name of a module for which debugging information should be printed. Possible arguments for debug can be found by looking for calls to Util.debug in the sources (using, e.g., grep). Setting -debug all causes information from all modules to be printed (this mode of usage is the first one to try, if you are trying to understand something that Unison seems to be doing wrong); -debug verbose turns on some additional debugging output from some modules (e.g., it will show exactly what bytes are being sent across the network). diff xxx This preference can be used to control the name and command-line arguments of the system utility used to generate displays of file differences. The default is `diff -u CURRENT2 CURRENT1'. If the value of this preference contains the substrings CURRENT1 and CURRENT2, these will be replaced by the names of the files to be diffed. If not, the two filenames will be appended to the command. In both cases, the filenames are suitably quoted. doc xxx The command-line argument -doc secname causes unison to display section secname of the manual on the standard output and then exit. Use -doc all to display the whole manual, which includes exactly the same information as the printed and HTML manuals, modulo formatting. Use -doc topics to obtain a list of the names of the various sections that can be printed. dumbtty When set to true, this flag makes the text mode user interface avoid trying to change any of the terminal settings. (Normally, Unison puts the terminal in `raw mode', so that it can do things like overwriting the current line.) This is useful, for example, when Unison runs in a shell inside of Emacs. When dumbtty is set, commands to the user interface need to be followed by a carriage return before Unison will execute them. (When it is off, Unison recognizes keystrokes as soon as they are typed.) This preference has no effect on the graphical user interface. dumparchives When this preference is set, Unison will create a file unison.dump on each host, containing a text summary of the archive, immediately after loading it. fastcheck xxx When this preference is set to true, Unison will use the modification time and length of a file as a `pseudo inode number' when scanning replicas for updates, instead of reading the full contents of every file. Under Windows, this may cause Unison to miss propagating an update if the modification time and length of the file are both unchanged by the update. However, Unison will never overwrite such an update with a change from the other replica, since it always does a safe check for updates just before propagating a change. Thus, it is reasonable to use this switch under Windows most of the time and occasionally run Unison once with fastcheck set to false, if you are worried that Unison may have overlooked an update. The default value of the preference is auto, which causes Unison to use fast checking on Unix replicas (where it is safe) and slow checking on Windows replicas. For backward compatibility, yes, no, and default can be used in place of true, false, and auto. See the section "Fast Checking" for more information. follow xxx Including the preference -follow pathspec causes Unison to treat symbolic links matching pathspec as `invisible' and behave as if the object pointed to by the link had appeared literally at this position in the replica. See the section "Symbolic Links" for more details. The syntax of pathspec> is described in the section "Path Specification" . force xxx Including the preference -force root causes Unison to resolve all differences (even non-conflicting changes) in favor of root. This effectively changes Unison from a synchronizer into a mirroring utility. You can also specify -force newer (or -force older) to force Unison to choose the file with the later (earlier) modtime. In this case, the -times preference must also be enabled. This preference is overridden by the forcepartial preference. This preference should be used only if you are sure you know what you are doing! forcepartial xxx Including the preference forcepartial PATHSPEC -> root causes Unison to resolve all differences (even non-conflicting changes) in favor of root for the files in PATHSPEC (see the section "Path Specification" for more information). This effectively changes Unison from a synchronizer into a mirroring utility. You can also specify forcepartial PATHSPEC -> newer (or forcepartial PATHSPEC older) to force Unison to choose the file with the later (earlier) modtime. In this case, the -times preference must also be enabled. This preference should be used only if you are sure you know what you are doing! group When this flag is set to true, the group attributes of the files are synchronized. Whether the group names or the group identifiers are synchronizeddepends on the preference numerids. height n Used to set the height (in lines) of the main window in the graphical user interface. ignore xxx Including the preference -ignore pathspec causes Unison to completely ignore paths that match pathspec (as well as their children). This is useful for avoiding synchronizing temporary files, object files, etc. The syntax of pathspec is described in the section "Path Specification" , and further details on ignoring paths is found in the section "Ignoring Paths" . ignorecase xxx When set to true, this flag causes Unison to treat filenames as case insensitive--i.e., files in the two replicas whose names differ in (upper- and lower-case) `spelling' are treated as the same file. When the flag is set to false, Unison will treat all filenames as case sensitive. Ordinarily, when the flag is set to t default, filenames are automatically taken to be case-insensitive if either host is running Windows or OSX. In rare circumstances it is useful to set the flag manually (e.g. when running Unison on a Unix system with a FAT [Windows] volume mounted). ignorelocks When this preference is set, Unison will ignore any lock files that may have been left over from a previous run of Unison that was interrupted while reading or writing archive files; by default, when Unison sees these lock files it will stop and request manualintervention. This option should be set only if you are positive that no other instance of Unison might be concurrently accessing the same archive files (e.g., because there was only one instance of unison running and it has just crashed or you have just killed it). It is probably not a good idea to set this option in a profile: it is intended for command-line use. ignorenot xxx This preference overrides the preference ignore. It gives a list of patterns (in the same format as ignore) for paths that should definitely not be ignored, whether or not they happen to match one of the ignore patterns. Note that the semantics of ignore and ignorenot is a little counter-intuitive. When detecting updates, Unison examines paths in depth-first order, starting from the roots of the replicas and working downwards. Before examining each path, it checks whether it matches ignore and does not match ignorenot; in this case it skips this path and all its descendants. This means that, if some parent of a given path matches an ignore pattern, then it will be skipped even if the path itself matches an ignorenot pattern. In particular, putting ignore = Path * in your profile and then using t ignorenot to select particular paths to be synchronized will not work. Instead, you should use the path preference to choose particular paths to synchronize. immutable xxx This preference specifies paths for directories whose children are all immutable files -- i.e., once a file has been created, its contents never changes. When scanning for updates, Unison does not check whether these files have been modified; this can speed update detection significantly (in particular, for mail directories). immutablenot xxx This preference overrides immutable. key xxx Used in a profile to define a numeric key (0-9) that can be used in the graphical user interface to switch immediately to this profile. killserver When set to true, this flag causes Unison to kill the remote server process when the synchronization is finished. This behavior is the default for ssh connections, so this preference is not normally needed when running over ssh; it is provided so that socket-mode servers can be killed off after a single run of Unison, rather than waiting to accept future connections. (Some users prefer to start a remote socket server for each run of Unison, rather than leaving one running all the time.) label xxx Used in a profile to provide a descriptive string documenting its settings. (This is useful for users that switch between several profiles, especially using the `fast switch' feature of the graphical user interface.) log When this flag is set, Unison will log all changes to the filesystems on a file. logfile xxx By default, logging messages will be appended to the file unison.log in your HOME directory. Set this preference if you prefer another file. maxbackups n This preference specifies the number of backup versions that will be kept by unison, for each path that matches the predicate backup. The default is 2. maxthreads n This preference controls how much concurrency is allowed during the transport phase. Normally, it should be set reasonably high (default is 20) to maximize performance, but when Unison is used over a low-bandwidth link it may be helpful to set it lower (e.g. to 1) so that Unison doesn't soak up all the available bandwidth. merge xxx This preference can be used to run a merge program which will create a new version for each of the files and the backup, with the last backup and the both replicas. Setting the merge preference for a path will also cause this path to be backed up, just like t backup. The syntax of pathspec>cmd is described in the section "Path Specification" , and further details on Merging functions are present in the section "Merging files" . mountpoint xxx Including the preference -mountpoint PATH causes Unison to double-check, at the end of update detection, that PATH exists and abort if it does not. This is useful when Unison is used to synchronize removable media. This preference can be given more than once. See the section "Mount Points" . numericids When this flag is set to true, groups and users are synchronized numerically, rather than by name. The special uid 0 and the special group 0 are never mapped via user/group names even if this preference is not set. owner When this flag is set to true, the owner attributes of the files are synchronized. Whether the owner names or the owner identifiers are synchronizeddepends on the preference extttnumerids. path xxx When no path preference is given, Unison will simply synchronize the two entire replicas, beginning from the given pair of roots. If one or more path preferences are given, then Unison will synchronize only these paths and their children. (This is useful for doing a fast sync of just one directory, for example.) Note that path preferences are intepreted literally--they are not regular expressions. perms n The integer value of this preference is a mask indicating which permission bits should be synchronized. It is set by default to 0o1777: all bits but the set-uid and set-gid bits are synchronised (synchronizing theses latter bits can be a security hazard). If you want to synchronize all bits, you can set the value of this preference to -1. prefer xxx Including the preference -prefer root causes Unison always to resolve conflicts in favor of root, rather than asking for guidance from the user. (The syntax of root is the same as for the root preference, plus the special values newer and older.) This preference is overridden by the preferpartial preference. This preference should be used only if you are sure you know what you are doing! preferpartial xxx Including the preference preferpartial PATHSPEC -> root causes Unison always to resolve conflicts in favor of root, rather than asking for guidance from the user, for the files in PATHSPEC (see the section "Path Specification" for more information). (The syntax of root is the same as for the root preference, plus the special values newer and older.) This preference should be used only if you are sure you know what you are doing! pretendwin When set to true, this preference makes Unison use Windows-style fast update detection (using file creation times as "pseudo-inode-numbers"), even when running on a Unix system. This switch should be used with care, as it is less safe than the standard update detection method, but it can be useful for synchronizing VFAT filesystems (which do not support inode numbers) mounted on Unix systems. The fastcheck option should also be set to true. repeat xxx Setting this preference causes the text-mode interface to synchronize repeatedly, rather than doing it just once and stopping. If the argument is a number, Unison will pause for that many seconds before beginning again. retry n Setting this preference causes the text-mode interface to try again to synchronize updated paths where synchronization fails. Each such path will be tried N times. root xxx Each use of this preference names the root of one of the replicas for Unison to synchronize. Exactly two roots are needed, so normal modes of usage are either to give two values for root in the profile, or to give no values in the profile and provide two on the command line. Details of the syntax of roots can be found in the section "Roots" . The two roots can be given in either order; Unison will sort them into a canonical order before doing anything else. It also tries to `canonize' the machine names and paths that appear in the roots, so that, if Unison is invoked later with a slightly different name for the same root, it will be able to locate the correct archives. rootalias xxx When calculating the name of the archive files for a given pair of roots, Unison replaces any roots matching the left-hand side of any rootalias rule by the corresponding right-hand side. rshargs xxx The string value of this preference will be passed as additional arguments (besides the host name and the name of the Unison executable on the remote system) to the rsh command used to invoke the remote server. rshcmd xxx This preference can be used to explicitly set the name of the rsh executable (e.g., giving a full path name), if necessary. rsrc xxx When set to true, this flag causes Unison to synchronize resource forks and HFS meta-data. On filesystems that do not natively support resource forks, this data is stored in Carbon-compatible ._ AppleDouble files. When the flag is set to false, Unison will not synchronize these data. Ordinarily, the flag is set to default, and these data are automatically synchronized if either host is running OSX. In rare circumstances it is useful to set the flag manually. rsync Unison uses the 'rsync algorithm' for 'diffs-only' transfer of updates to large files. Setting this flag to false makes Unison use whole-file transfers instead. Under normal circumstances, there is no reason to do this, but if you are having trouble with repeated 'rsync failure' errors, setting it to false should permit you to synchronize the offending files. selftest Run internal tests and exit. This option is mostly for developers and must be used carefully: in particular, it will delete the contents of both roots, so that it can install its own files for testing. This flag only makes sense on the command line. When it is provided, no preference file is read: all preferences must be specified on thecommand line. Also, since the self-test procedure involves overwriting the roots and backup directory, the names of the roots and of the backupdir preference must include the string "test" or else the tests will be aborted. (If these are not given on the command line, dummy subdirectories in the current directory will be created automatically.) servercmd xxx This preference can be used to explicitly set the name of the Unison executable on the remote server (e.g., giving a full path name), if necessary. showarchive When this preference is set, Unison will print out the 'true names'of the roots, in the same form as is expected by the rootaliaspreference. silent When this preference is set to true, the textual user interface will print nothing at all, except in the case of errors. Setting silent to true automatically sets the batch preference to true. sortbysize When this flag is set, the user interface will list changed files by size (smallest first) rather than by name. This is useful, for example, for synchronizing over slow links, since it puts very large files at the end of the list where they will not prevent smaller files from being transferred quickly. This preference (as well as the other sorting flags, but not the sorting preferences that require patterns as arguments) can be set interactively and temporarily using the 'Sort' menu in the graphical user interface. sortfirst xxx Each argument to sortfirst is a pattern pathspec, which describes a set of paths. Files matching any of these patterns will be listed first in the user interface. The syntax of pathspec is described in the section "Path Specification" . sortlast xxx Similar to sortfirst, except that files matching one of these patterns will be listed at the very end. sortnewfirst When this flag is set, the user interface will list newly created files before all others. This is useful, for example, for checking that newly created files are not `junk', i.e., ones that should be ignored or deleted rather than synchronized. sshargs xxx The string value of this preference will be passed as additional arguments (besides the host name and the name of the Unison executable on the remote system) to the ssh command used to invoke the remote server. sshcmd xxx This preference can be used to explicitly set the name of the ssh executable (e.g., giving a full path name), if necessary. sshversion xxx This preference can be used to control which version of ssh should be used to connect to the server. Legal values are 1 and 2, which will cause unison to try to use ssh1 orssh2 instead of just ssh to invoke ssh. The default value is empty, which will make unison use whatever version of ssh is installed as the default `ssh' command. terse When this preference is set to true, the user interface will not print status messages. testserver Setting this flag on the command line causes Unison to attempt to connect to the remote server and, if successful, print a message and immediately exit. Useful for debugging installation problems. Should not be set in preference files. times When this flag is set to true, file modification times (but not directory modtimes) are propagated. ui xxx This preference selects either the graphical or the textual user interface. Legal values are graphic or text. Because this option is processed specially during Unison's start-up sequence, it can only be used on the command line. In preference files it has no effect. If the Unison executable was compiled with only a textual interface, this option has no effect. (The pre-compiled binaries are all compiled with both interfaces available.) version Print the current version number and exit. (This option only makes sense on the command line.) xferbycopying When this preference is set, Unison will try to avoid transferring file contents across the network by recognizing when a file with the required contents already exists in the target replica. This usually allows file moves to be propagated very quickly. The default value istrue. Profiles A profile is a text file that specifies permanent settings for roots, paths, ignore patterns, and other preferences, so that they do not need to be typed at the command line every time Unison is run. Profiles should reside in the .unison directory on the client machine. If Unison is started with just one argument name on the command line, it looks for a profile called name.prf in the .unison directory. If it is started with no arguments, it scans the .unison directory for files whose names end in .prf and offers a menu (provided that the Unison executable is compiled with the graphical user interface). If a file named default.prf is found, its settings will be offered as the default choices. To set the value of a preference p permanently, add to the appropriate profile a line of the form p = true for a boolean flag or p = for a preference of any other type. Whitespaces around p and xxx are ignored. A profile may also include blank lines and lines beginning with #; both are ignored. When Unison starts, it first reads the profile and then the command line, so command-line options will override settings from the profile. Profiles may also include lines of the form include name, which will cause the file name (or name.prf, if name does not exist in the .unison directory) to be read at the point, and included as if its contents, instead of the include line, was part of the profile. Include lines allows settings common to several profiles to be stored in one place. A profile may include a preference `label = desc' to provide a description of the options selected in this profile. The string desc is listed along with the profile name in the profile selection dialog, and displayed in the top-right corner of the main Unison window in the graphical user interface. The graphical user-interface also supports one-key shortcuts for commonly used profiles. If a profile contains a preference of the form `key = n', where n is a single digit, then pressing this digit key will cause Unison to immediately switch to this profile and begin synchronization again from scratch. In this case, all actions that have been selected for a set of changes currently being displayed will be discarded. Sample Profiles A Minimal Profile Here is a very minimal profile file, such as might be found in .unison/default.prf: # Roots of the synchronization root = /home/bcpierce root = ssh://saul//home/bcpierce # Paths to synchronize path = current path = common path = .netscape/bookmarks.html A Basic Profile Here is a more sophisticated profile, illustrating some other useful features. # Roots of the synchronization root = /home/bcpierce root = ssh://saul//home/bcpierce # Paths to synchronize path = current path = common path = .netscape/bookmarks.html # Some regexps specifying names and paths to ignore ignore = Name temp.* ignore = Name *~ ignore = Name .*~ ignore = Path */pilot/backup/Archive_* ignore = Name *.o ignore = Name *.tmp # Window height height = 37 # Keep a backup copy of every file in a central location backuplocation = central backupdir = /home/bcpierce/backups backup = Name * backupprefix = $VERSION. backupsuffix = # Use this command for displaying diffs diff = diff -y -W 79 --suppress-common-lines # Log actions to the terminal log = true A Power-User Profile When Unison is used with large replicas, it is often convenient to be able to synchronize just a part of the replicas on a given run (this saves the time of detecting updates in the other parts). This can be accomplished by splitting up the profile into several parts -- a common part containing most of the preference settings, plus one "top-level" file for each set of paths that need to be synchronized. (The include mechanism can also be used to allow the same set of preference settings to be used with different roots.) The collection of profiles implementing this scheme might look as follows. The file default.prf is empty except for an include directive: # Include the contents of the file common include common Note that the name of the common file is common, not common.prf; this prevents Unison from offering common as one of the list of profiles in the opening dialog (in the graphical UI). The file common contains the real preferences: # Roots of the synchronization root = /home/bcpierce root = ssh://saul//home/bcpierce # (... other preferences ...) # If any new preferences are added by Unison (e.g. 'ignore' # preferences added via the graphical UI), then store them in the # file 'common' rathen than in the top-level preference file addprefsto = common # Names and paths to ignore: ignore = Name temp.* ignore = Name *~ ignore = Name .*~ ignore = Path */pilot/backup/Archive_* ignore = Name *.o ignore = Name *.tmp Note that there are no path preferences in common. This means that, when we invoke Unison with the default profile (e.g., by typing 'unison default' or just 'unison' on the command line), the whole replicas will be synchronized. (If we never want to synchronize the whole replicas, then default.prf would instead include settings for all the paths that are usually synchronized.) To synchronize just part of the replicas, Unison is invoked with an alternate preference file--e.g., doing 'unison workingset', where the preference file workingset.prf contains path = current/papers path = Mail/inbox path = Mail/drafts include common causes Unison to synchronize just the listed subdirectories. The key preference can be used in combination with the graphical UI to quickly switch between different sets of paths. For example, if the file mail.prf contains path = Mail batch = true key = 2 include common then pressing 2 will cause Unison to look for updates in the Mail subdirectory and (because the batch flag is set) immediately propagate any that it finds. Keeping Backups When Unison overwrites a file or directory by propagating a new version from the other replica, it can keep the old version around as a backup. There are several preferences that control precisely where these backups are stored and how they are named. To enable backups, you must give one or more backup preferences. Each of these has the form backup = where has the same form as for the ignore preference. For example, backup = Name * causes Unison to keep backups of all files and directories. The backupnot preference can be used to give a few exceptions: it specifies which files and directories should not be backed up, even if they match the backup pathspec. It is important to note that the pathspec is matched against the path that is being updated by Unison, not its descendants. For example, if you set backup = Name *.txt and then delete a whole directory named foo containing some text files, these files will not be backed up because Unison will just check that foo does not match *.txt. Similarly, if the directory itself happened to be called foo.txt, then the whole directory and all the files in it will be backed up, regardless of their names. Backup files can be stored either centrally or locally. This behavior is controlled by the preference backuplocation, whose value must be either central or local. (The default is central.) When backups are stored locally, they are kept in the same directory as the original. When backups are stored centrally, the directory used to hold them is controlled by the preference backupdir and the environment variable UNISONBACKUPDIR. (The environment variable is checked first.) If neither of these are set, then the directory .unison/backup in the user's home directory is used. The preference maxbackups controls how many previous versions of each file are kept (including the current version). By default, backup files are named .bak.VERSION.FILENAME, where FILENAME is the original filename and VERSION is the backup number (1 for the most recent, 2 for the next most recent, etc.). This can be changed by setting the preferences backupprefix and/or backupsuffix. If desired, backupprefix may include a directory prefix; this can be used with backuplocation = local to put all backup files for each directory into a single subdirectory. For example, setting backuplocation = local backupprefix = .unison/$VERSION. backupsuffix = will put all backups in a local subdirectory named .unison. Also, note that the string $VERSION in either backupprefix or backupsuffix (it must appear in one or the other) is replaced by the version number. This can be used, for example, to ensure that backup files retain the same extension as the originals. For backward compatibility, the backups preference is also supported. It simply means backup = Name * and backuplocation = local. Merging Conflicting Versions Unison can invoke external programs to merge conflicting versions of a file. The preference merge controls this process. The merge preference may be given once or several times in a preference file (it can also be given on the command line, of course, but this tends to be awkward because of the spaces and special characters involved). Each instance of the preference looks like this: merge = -> The here has exactly the same format as for the ignore preference (see the section "Path specification" ). For example, using "Name *.txt" as the tells Unison that this command should be used whenever a file with extension .txt needs to be merged. Many external merging programs require as inputs not just the two files that need to be merged, but also a file containing the last synchronized version. You can ask Unison to keep a copy of the last synchronized version for some files using the backupcurrent preference. This preference is used in exactly the same way as backup and its meaning is similar, except that it causes backups to be kept of the current contents of each file after it has been synchronized by Unison, rather than the previous contents that Unison overwrote. These backups are kept on both replicas in the same place as ordinary backup files--i.e. according to the backuplocation and backupdir preferences. They are named like the original files if backupslocation is set to 'central' and otherwise, Unison uses the backupprefix and backupsuffix preferences and assumes a version number 000 for these backups. The part of the preference specifies what external command should be invoked to merge files at paths matching the . Within this string, several special substrings are recognized; these will be substituted with appropriate values before invoking a sub-shell to execute the command. * CURRENT1 is replaced by the name of (a temporary copy of) the local variant of the file. * CURRENT2 is replaced by the name of a temporary file, into which the contents of the remote variant of the file have been transferred by Unison prior to performing the merge. * CURRENTARCH is replaced by the name of the backed up copy of the original version of the file (i.e., the file saved by Unison if the current filename matches the path specifications for the backupcurrent preference, as explained above), if one exists. If no archive exists and CURRENTARCH appears in the merge command, then an error is signalled. * CURRENTARCHOPT is replaced by the name of the backed up copy of the original version of the file (i.e., its state at the end of the last successful run of Unison), if one exists, or the empty string if no archive exists. * NEW is replaced by the name of a temporary file that Unison expects to be written by the merge program when it finishes, giving the desired new contents of the file. * PATH is replaced by the path (relative to the roots of the replicas) of the file being merged. * NEW1 and NEW2 are replaced by the names of temporary files that Unison expects to be written by the merge program when it is only able to partially merge the originals; in this case, NEW1 will be written back to the local replica and NEW2 to the remote replica; NEWARCH, if present, will be used as the "last common state" of the replicas. (These three options are provided for later compatibility with the Harmony data synchronizer.) To accomodate the wide variety of programs that users might want to use for merging, Unison checks for several possible situations when the merge program exits: * If the merge program exits with a non-zero status, then merge is considered to have failed and the replicas are not changed. * If the file NEW has been created, it is written back to both replicas (and stored in the backup directory). Similarly, if just the file NEW1 has been created, it is written back to both replicas. * If neither NEW nor NEW1 have been created, then Unison examines the temporary files CURRENT1 and CURRENT2 that were given as inputs to the merge program. If either has been changed (or both have been changed in identical ways), then its new contents are written back to both replicas. If either CURRENT1 or CURRENT2 has been deleted, then the contents of the other are written back to both replicas. * If the files NEW1, NEW2, and NEWARCH have all been created, they are written back to the local replica, remote replica, and backup directory, respectively. If the files NEW1, NEW2 have been created, but NEWARCH has not, then these files are written back to the local replica and remote replica, respectively. Also, if NEW1 and NEW2 have identical contents, then the same contents are stored as a backup (if the backupcurrent preference is set for this path) to reflect the fact that the path is currently in sync. * If NEW1 and NEW2 (resp. CURRENT1 and CURRENT2) are created (resp. overwritten) with different contents but the merge command did not fail (i.e., it exited with status code 0), then we copy NEW1 (resp. CURRENT1) to the other replica and to the archive. This behavior is a design choice made to handle the case where a merge command only synchronizes some specific contents between two files, skipping some irrelevant information (order between entries, for instance). We assume that, if the merge command exits normally, then the two resulting files are "as good as equal." (The reason we copy one on top of the other is to avoid Unison detecting that the files are unequal the next time it is run and trying again to merge them when, in fact, the merge program has already made them as similar as it is able to.) If the confirmmerge preference is set and Unison is not run in batch mode, then Unison will always ask for confirmation before actually committing the results of the merge to the replicas. A large number of external merging programs are available. For example, on Unix systems setting the merge preference to merge = Name *.txt -> diff3 CURRENT1 CURRENTARCH CURRENT2 -m > NEW will tell Unison to use the external diff3 program for merging. Alternatively, users of emacs may find the following settings convenient: merge = Name *.txt -> emacs -q --eval '(ediff-merge-files-with-ancestor "CURRENT1" "CURRENT2" "CURRENTARCH" nil "NEW")' (These commands are displayed here on two lines to avoid running off the edge of the page. In your preference file, each command should be written on a single line.) Users running emacs under windows may find something like this useful: merge = Name * -> C:\Progra~1\Emacs\emacs\bin\emacs.exe -q --eval "(ediff-files """CURRENT1""" """CURRENT2""")" Users running Mac OS X (you may need the Developer Tools installed to get the opendiff utility) may prefer merge = Name *.txt -> opendiff CURRENT1 CURRENT2 -ancestor CURRENTARCH -mer ge NEW Here is a slightly more involved hack. The opendiff program can operate either with or without an archive file. A merge command of this form merge = Name *.txt -> if [ CURRENTARCHOPTx = x ]; then opendiff CURRENT1 CURRENT2 -merge NEW; else opendiff CURRENT1 CURRENT2 -ancestor CURRENTARCHOPT -merge N EW; fi (still all on one line in the preference file!) will test whether an archive file exists and use the appropriate variant of the arguments to opendiff. Ordinarily, external merge programs are only invoked when Unison is not running in batch mode. To specify an external merge program that should be used no matter the setting of the batch flag, use the mergebatch preference instead of merge. Please post suggestions for other useful values of the merge preference to the unison-users mailing list--we'd like to give several examples here. The User Interface Both the textual and the graphical user interfaces are intended to be mostly self-explanatory. Here are just a few tricks: * By default, when running on Unix the textual user interface will try to put the terminal into the "raw mode" so that it reads the input a character at a time rather than a line at a time. (This means you can type just the single keystroke ">" to tell Unison to propagate a file from left to right, rather than "> Enter.") There are some situations, though, where this will not work -- for example, when Unison is running in a shell window inside Emacs. Setting the dumbtty preference will force Unison to leave the terminal alone and process input a line at a time. Exit code When running in the textual mode, Unison returns an exit status, which describes whether, and at which level, the synchronization was successful. The exit status could be useful when Unison is invoked from a script. Currently, there are four possible values for the exit status: * 0: successful synchronization; everything is up-to-date now. * 1: some files were skipped, but all file transfers were successful. * 2: non-fatal failures occurred during file transfer. * 3: a fatal error occurred, or the execution was interrupted. The graphical interface does not return any useful information through the exit status. Path specification Several Unison preferences (e.g., ignore/ignorenot, follow, sortfirst/sortlast, backup, merge, etc.) specify individual paths or sets of paths. These preferences share a common syntax based on regular-expressions. Each preference is associated with a list of path patterns; the paths specified are those that match any one of the path pattern. * Pattern preferences can be given on the command line, or, more often, stored in profiles, using the same syntax as other preferences. For example, a profile line of the form ignore = pattern adds pattern to the list of patterns to be ignored. * Each pattern can have one of three forms. The most general form is a Posix extended regular expression introduced by the keyword Regex. (The collating sequences and character classes of full Posix regexps are not currently supported). Regex regexp For convenience, two other styles of pattern are also recognized: Name name matches any path in which the last component matches name, while Path path matches exactly the path path. The name and path arguments of the latter forms of patterns are not regular expressions. Instead, standard "globbing" conventions can be used in name and path: + a * matches any sequence of characters not including / (and not beginning with ., when used at the beginning of a name) + a ? matches any single character except / (and leading .) + [xyz] matches any character from the set {x, y, z } + {a,bb,ccc} matches any one of a, bb, or ccc. * The path separator in path patterns is always the forward-slash character "/" -- even when the client or server is running under Windows, where the normal separator character is a backslash. This makes it possible to use the same set of path patterns for both Unix and Windows file systems. Some examples of path patterns appear in the section "Ignoring Paths" . Ignoring Paths Most users of Unison will find that their replicas contain lots of files that they don't ever want to synchronize -- temporary files, very large files, old stuff, architecture-specific binaries, etc. They can instruct Unison to ignore these paths using patterns introduced in the section "Path Patterns" . For example, the following pattern will make Unison ignore any path containing the name CVS or a name ending in .cmo: ignore = Name {CVS,*.cmo} The next pattern makes Unison ignore the path a/b: ignore = Path a/b Path patterns do not skip filesnames beginning with . (as Name patterns do). For example, ignore = Path */tmp will include .foo/tmp in the set of ignore directories, as it is a path, not a name, that is ignored. The following pattern makes Unison ignore any path beginning with a/b and ending with a name ending by .ml. ignore = Regex a/b/.*\.ml Note that regular expression patterns are "anchored": they must match the whole path, not just a substring of the path. Here are a few extra points regarding the ignore preference. * If a directory is ignored, all its descendents will be too. * The user interface provides some convenient commands for adding new patterns to be ignored. To ignore a particular file, select it and press "i". To ignore all files with the same extension, select it and press "E" (with the shift key). To ignore all files with the same name, no matter what directory they appear in, select it and press "N". These new patterns become permanent: they are immediately added to the current profile on disk. * If you use the include directive to include a common collection of preferences in several top-level preference files, you will probably also want to set the addprefsto preference to the name of this file. This will cause any new ignore patterns that you add from inside Unison to be appended to this file, instead of whichever top-level preference file you started Unison with. * Ignore patterns can also be specified on the command line, if you like (this is probably not very useful), using an option like -ignore 'Name temp.txt'. * Be careful about renaming directories containing ignored files. Because Unison understands the rename as a delete plus a create, any ignored files in the directory will be lost (since they are invisible to Unison and therefore they do not get recreated in the new version of the directory). * There is also an ignorenot preference, which specifies a set of patterns for paths that should not be ignored, even if they match an ignore pattern. However, the interaction of these two sets of patterns can be a little tricky. Here is exactly how it works: + Unison starts detecting updates from the root of the replicas--i.e., from the empty path. If the empty path matches an ignore pattern and does not match an ignorenot pattern, then the whole replica will be ignored. (For this reason, it is not a good idea to include Name * as an ignore pattern. If you want to ignore everything except a certain set of files, use Name ?*.) + If the root is a directory, Unison continues looking for updates in all the immediate children of the root. Again, if the name of some child matches an ignore pattern and does not match an ignorenot pattern, then this whole path including everything below it will be ignored. + If any of the non-ignored children are directories, then the process continues recursively. Symbolic Links Ordinarily, Unison treats symbolic links in Unix replicas as "opaque": it considers the contents of the link to be just the string specifying where the link points, and it will propagate changes in this string to the other replica. It is sometimes useful to treat a symbolic link "transparently," acting as though whatever it points to were physically in the replica at the point where the symbolic link appears. To tell Unison to treat a link in this manner, add a line of the form follow = pathspec to the profile, where pathspec is a path pattern as described in the section "Path Patterns" . Windows file systems do not support symbolic links; Unison will refuse to propagate an opaque symbolic link from Unix to Windows and flag the path as erroneous. When a Unix replica is to be synchronized with a Windows system, all symbolic links should match either an ignore pattern or a follow pattern. Permissions Synchronizing the permission bits of files is slightly tricky when two different filesytems are involved (e.g., when synchronizing a Windows client and a Unix server). In detail, here's how it works: * When the permission bits of an existing file or directory are changed, the values of those bits that make sense on both operating systems will be propagated to the other replica. The other bits will not be changed. * When a newly created file is propagated to a remote replica, the permission bits that make sense in both operating systems are also propagated. The values of the other bits are set to default values (they are taken from the current umask, if the receiving host is a Unix system). * For security reasons, the Unix setuid and setgid bits are not propagated. * The Unix owner and group ids are not propagated. (What would this mean, in general?) All files are created with the owner and group of the server process. Cross-Platform Synchronization If you use Unison to synchronize files between Windows and Unix systems, there are a few special issues to be aware of. Case conflicts. In Unix, filenames are case sensitive: foo and FOO can refer to different files. In Windows, on the other hand, filenames are not case sensitive: foo and FOO can only refer to the same file. This means that a Unix foo and FOO cannot be synchronized onto a Windows system -- Windows won't allow two different files to have the "same" name. Unison detects this situation for you, and reports that it cannot synchronize the files. You can deal with a case conflict in a couple of ways. If you need to have both files on the Windows system, your only choice is to rename one of the Unix files to avoid the case conflict, and re-synchronize. If you don't need the files on the Windows system, you can simply disregard Unison's warning message, and go ahead with the synchronization; Unison won't touch those files. If you don't want to see the warning on each synchronization, you can tell Unison to ignore the files (see the section "Ignore" ). Illegal filenames. Unix allows some filenames that are illegal in Windows. For example, colons (`:') are not allowed in Windows filenames, but they are legal in Unix filenames. This means that a Unix file foo:bar can't be synchronized to a Windows system. As with case conflicts, Unison detects this situation for you, and you have the same options: you can either rename the Unix file and re-synchronize, or you can ignore it. Slow Links Unison is built to run well even over relatively slow links such as modems and DSL connections. Unison uses the "rsync protocol" designed by Andrew Tridgell and Paul Mackerras to greatly speed up transfers of large files in which only small changes have been made. More information about the rsync protocol can be found at the rsync web site (http://samba.anu.edu.au/rsync/). If you are using Unison with ssh, you may get some speed improvement by enabling ssh's compression feature. Do this by adding the option "-rshargs -C" to the command line or "rshargs = -C" to your profile. Fast Update Detection If your replicas are large and at least one of them is on a Windows system, you may find that Unison's default method for detecting changes (which involves scanning the full contents of every file on every sync--the only completely safe way to do it under Windows) is too slow. Unison provides a preference fastcheck that, when set to true, causes it to use file creation times as 'pseudo inode numbers' when scanning replicas for updates, instead of reading the full contents of every file. When fastcheck is set to no, Unison will perform slow checking--re-scanning the contents of each file on each synchronization--on all replicas. When fastcheck is set to default (which, naturally, is the default), Unison will use fast checks on Unix replicas and slow checks on Windows replicas. This strategy may cause Unison to miss propagating an update if the modification time and length of the file are both unchanged by the update. However, Unison will never overwrite such an update with a change from the other replica, since it always does a safe check for updates just before propagating a change. Thus, it is reasonable to use this switch most of the time and occasionally run Unison once with fastcheck set to no, if you are worried that Unison may have overlooked an update. Fastcheck is (always) automatically disabled for files with extension .xls or .mpp, to prevent Unison from being confused by the habits of certain programs (Excel, in particular) of updating files without changing their modification times. Mount Points and Removable Media Using Unison removable media such as USB drives can be dangerous unless you are careful. If you synchronize a directory that is stored on removable media when the media is not present, it will look to Unison as though the whole directory has been deleted, and it will proceed to delete the directory from the other replica--probably not what you want! To prevent accidents, Unison provides a preference called mountpoint. Including a line like mountpoint = /mnt/foo in your preference file will cause Unison to check, after it finishes detecting updates, that something actually exists at the path /mnt/foo on both replicas; if it does not, the Unison run will abort. ATTRIBUTES ---------- See attributes(5) for descriptions of the following attributes: _______________________________________ | ATTRIBUTE TYPE | ATTRIBUTE VALUE| |_______________________________________ | Availability | SUNWunison | |_______________________________________ | Interface Stability| Uncommitted | |____________________|_________________| NOTES ----- Source for unison is available at http://www.cis.upenn.edu/~bcpierce/unison.