UNISON(1) User's Reference Manual UNISON(1)
NAME
unison — a multi-platform bi-directional file synchronization tool
SYNOPSIS
unison [options]
unison root1 root2 [options]
unison profilename [options]
DESCRIPTION
Unison is a file-synchronization tool for POSIX-compliant systems (e.g.
*BSD and GNU/Linux), macOS and Windows. It allows two replicas of a col-
lection of files and directories to be stored on different hosts (or dif-
ferent disks on the same host), modified separately, and then brought up
to date by propagating the changes in each replica to the other.
Unison has been in use for over 20 years and many people use it to syn-
chronize data they care about.
Unison shares a number of features with other tools. Some of the distin-
guishing features are:
• Unlike simple mirroring or backup utilities, Unison can deal with up-
dates to both replicas of a distributed directory structure.
• Unison works across platforms, allowing you to synchronize a Windows
laptop with a Unix server, for example.
• Unlike most distributed filesystems, Unison is a user-level program
that simply uses normal systems calls: there is no need to modify the
kernel, to have superuser privileges on either host, or to have a
FUSE implementation.
• Unison works between any pair of machines connected to the internet,
typically communicating over ssh(1), but also directly over TCP. It
is careful with network bandwidth, and runs well over slow links.
Transfers of small updates to large files are optimized using a com-
pression protocol similar to rsync(1).
• Unison is resilient to failure. It is careful to leave the replicas
and its own private structures in a sensible state at all times, even
in case of abnormal termination or communication failures.
OPTION SUMMARY
Basic options:
General:
-doc xxx show documentation ('-doc topics' lists topics)
-version print version and exit
What to sync:
-group synchronize group attributes
-ignore xxx add a pattern to the ignore list
-ignorenot xxx add a pattern to the ignorenot list
-nocreation xxx prevent file creations on one replica
-nodeletion xxx prevent file deletions on one replica
-noupdate xxx prevent file updates and deletions on one replica
-owner synchronize owner
-path xxx path to synchronize
-perms n part of the permissions which is synchronized
-root xxx root of a replica (should be used exactly twice)
-times synchronize modification times
How to sync:
-batch batch mode: ask no questions at all
How to sync (text interface (CLI) only):
-auto automatically accept default (nonconflicting) actions
-silent print nothing except error messages
-terse suppress status messages
Text interface (CLI):
-i interactive profile mode (text UI); command-line only
Advanced options:
Fine-tune sync:
-atomic xxx add a pattern to the atomic list
-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
-ignorecase xxx identify upper/lowercase filenames (true/false/default)
-immutable xxx add a pattern to the immutable list
-immutablenot xxx add a pattern to the immutablenot list
-links xxx allow the synchronization of symbolic links
(true/false/default)
-merge xxx add a pattern to the merge list
-nocreationpartial xxx add a pattern to the nocreationpartial list
-nodeletionpartial xxx add a pattern to the nodeletionpartial list
-noupdatepartial xxx add a pattern to the noupdatepartial list
-prefer xxx choose this replica's version for conflicting changes
-preferpartial xxx add a pattern to the preferpartial list
-rsrc xxx synchronize resource forks (true/false/default)
How to sync:
-backup xxx add a pattern to the backup list
-backupcurr xxx add a pattern to the backupcurr list
-backupcurrnot xxx add a pattern to the backupcurrnot list
-backupdir xxx directory for storing centralized backups
-backuploc 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 (deprecated) keep backup copies of all files (see also
'backup')
-backupsuffix xxx a suffix to be added to names of backup files
-confirmbigdel ask about whole-replica (or path) deletes (default true)
-confirmmerge ask for confirmation before committing results of a merge
-copyonconflict keep copies of conflicting files
-dontchmod when set, never use the chmod system call
-fastcheck xxx do fast update detection (true/false/default)
-fat use appropriate options for FAT filesystems
-ignoreinodenumbers ignore inode number changes when detecting updates
-maxbackups n number of backed up versions of a file
-numericids don't map uid/gid values by user/group names
-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
How to sync (text interface (CLI) only):
-repeat xxx synchronize repeatedly (text interface only)
-retry n re-try failed synchronizations N times (text ui only)
Text interface (CLI):
-color xxx use color output for text UI (true/false/default)
-dumbtty do not change terminal settings in text UI
Graphical interface (GUI):
-height n height (in lines) of main window in graphical interface
Remote connections:
-addversionno add version number to name of unison on server
-clientHostName xxx set host name of client
-halfduplex (deprecated) force half-duplex communication with the
server
-killserver kill server when done (even when using sockets)
-listen xxx listen on this name or addr in server socket mode (can
repeat)
-rsync activate the rsync transfer mode (default true)
-servercmd xxx name of unison executable on remote server
-socket xxx act as a server on a socket
-sshargs xxx other arguments (if any) for remote shell command
-sshcmd xxx path to the ssh executable
-stream (deprecated) use a streaming protocol for transferring
file contents (default true)
-testserver exit immediately after the connection to the server
-xferbycopying optimize transfers using local copies (default true)
Archive management:
-ignorearchives ignore existing archive files
Other:
-addprefsto xxx file to add new prefs to
-contactquietly suppress the 'contacting server' message during startup
-copymax n maximum number of simultaneous copyprog transfers
-copyprog xxx external program for copying large files
-copyprogrest xxx variant of copyprog for resuming partial transfers
-copyquoterem xxx add quotes to remote file name for copyprog
(true/false/default)
-copythreshold n use copyprog on files bigger than this (if >=0, in Kb)
-diff xxx set command for showing differences between files
-ignorelocks ignore locks left over from previous run (dangerous!)
-include xxx include a profile's preferences
-key xxx define a keyboard shortcut for this profile (in some UIs)
-label xxx provide a descriptive string label for this profile
-log record actions in logfile (default true)
-logfile xxx logfile name
-maxerrors n maximum number of errors before a directory transfer is
aborted
-maxsizethreshold n prevent transfer of files bigger than this (if >=0, in
Kb)
-maxthreads n maximum number of simultaneous file transfers
-mountpoint xxx abort if this path does not exist
-rootalias xxx register alias for canonical root names
-showarchive show 'true names' (for rootalias) of roots and archive
-source xxx include a file's preferences
-ui xxx select UI ('text' or 'graphic'); command-line only
-unicode xxx assume Unicode encoding in case insensitive mode
-watch when set, use a file watcher process to detect changes
Expert options:
-debug xxx debug module xxx ('all' -> everything, 'verbose' -> more)
-dumparchives dump contents of archives just after loading
-fastercheckUNSAFE skip computing fingerprints for new files (experts only!)
-selftest run internal tests and exit
OPTIONS
Most of the options can be given as command line arguments or in a pro-
file. On command line, but not in a profile, the options are specified
with a leading dash. Like this: -option.
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-currentmajorversionnumber instead of just unison as the
remote server command (note that the minor version number is
dropped -- e.g., unison-2.51). 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.
atomic xxx
This preference specifies paths for directories whose contents
will be considered as a group rather than individually when they
are both modified. The backups are also made atomically in this
case. The option backupcurr however has no effect on atomic
directories.
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; directories
(nor their permissions or any other metadata) are not backed up.
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 Section “Path Specification”
in the manual.
backupcurr xxx
Including the preference -backupcurr 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 Section “Merging
Conflicting Versions” in the manual. The syntax of pathspec is
described in Section “Path Specification” in the manual.
backupcurrnot xxx
Exceptions to backupcurr, 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.
backuploc 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.
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. One thing to
be careful of: If the backuploc preference is set to local,
Unison will automatically ignore all files whose prefix and
suffix match backupprefix and backupsuffix. So be careful to
choose values for these preferences that are sufficiently
different from the names of your real files.
backups
(Deprecated) 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.
clientHostName xxx
When specified, the host name of the client will not be guessed
and the provided host name will be used to find the archive.
color xxx
When set to true, this flag enables color output in text mode
user interface. When set to false, all color output is disabled.
Default is to enable color if the NO_COLOR environment variable
is not set.
confirmbigdel
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 committed 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.
Default is false.
contactquietly
If this flag is set, Unison will skip displaying the `Contacting
server' message (which some users find annoying) during startup.
copymax n
A number indicating how many instances of the external copying
utility Unison is allowed to run simultaneously (default to 1).
copyonconflict
When this flag is set, Unison will make a copy of files that
would otherwise be overwritten or deleted in case of conflicting
changes, and more generally whenever the default behavior is
overridden. This makes it possible to automatically resolve
conflicts in a fairly safe way when synchronizing continuously,
in combination with the -repeat watch and -prefer newer
preferences.
copyprog xxx
A string giving the name of an external program that can be used
to copy large files efficiently (plus command-line switches
telling it to copy files in-place). The default setting invokes
rsync with appropriate options—most users should not need to
change it.
copyprogrest xxx
A variant of copyprog that names an external program that should
be used to continue the transfer of a large file that has already
been partially transferred. Typically, copyprogrest will just be
copyprog with one extra option (e.g., --partial, for rsync). The
default setting invokes rsync with appropriate options—most users
should not need to change it.
copyquoterem xxx
When set to true, this flag causes Unison to add an extra layer
of quotes to the remote path passed to the external copy program.
This is needed by rsync, for example, which internally uses an
ssh connection requiring an extra level of quoting for paths
containing spaces. When this flag is set to default, extra quotes
are added if the value of copyprog contains the string rsync.
copythreshold n
A number indicating above what filesize (in kilobytes) Unison
should use the external copying utility specified by copyprog.
Specifying 0 will cause all copies to use the external program; a
negative number will prevent any files from using it. The default
is -1. See Section “Making Unison Faster on Large Files” in the
manual for more information.
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 OLDER NEWER'. 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
the value of this preference contains the substrings NEWER and
OLDER, these will be replaced by the names of files to be diffed,
NEWER being the most recently modified file of the two. Without
any of these substrings, the two filenames will be appended to
the command. In all 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.
dontchmod
By default, Unison uses the 'chmod' system call to set the
permission bits of files after it has copied them. But in some
circumstances (and under some operating systems), the chmod call
always fails. Setting this preference completely prevents Unison
from ever calling chmod.
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. (This does not apply to the very first
run, when Unison will always scan all files regardless of this
switch). 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. For backward compatibility, yes, no,
and default can be used in place of true, false, and auto. See
Section “Fast Update Detection” in the manual for more
information.
fastercheckUNSAFE
THIS FEATURE IS STILL EXPERIMENTAL AND SHOULD BE USED WITH
EXTREME CAUTION. When this flag is set to true, Unison will
compute a 'pseudo-fingerprint' the first time it sees a file
(either because the file is new or because Unison is running for
the first time). This enormously speeds update detection, but it
must be used with care, as it can cause Unison to miss conflicts:
If a given path in the filesystem contains files on both sides
that Unison has not yet seen, and if those files have the same
length but different contents, then Unison will not notice the
presence of a conflict. If, later, one of the files is changed,
the changed file will be propagated, overwriting the other.
Moreover, even when the files are initially identical, setting
this flag can lead to potentially confusing behavior: if a newly
created file is later touched without being modified, Unison will
treat this conservatively as a potential change (since it has no
record of the earlier contents) and show it as needing to be
propagated to the other replica. Most users should leave this
flag off -- the small time savings of not fingerprinting new
files is not worth the cost in terms of safety. However, it can
be very useful for power users with huge replicas that are known
to be already synchronized (e.g., because one replica is a newly
created duplicate of the other, or because they have previously
been synchronized with Unison but Unison's archives need to be
rebuilt). In such situations, it is recommended that this flag be
set only for the initial run of Unison, so that new archives can
be created quickly, and then turned off for normal use.
fat When this is set to true, Unison will use appropriate options to
synchronize efficiently and without error a replica located on a
FAT filesystem on a non-Windows machine: do not synchronize
permissions (perms = 0); never use chmod (dontchmod = true);
treat filenames as case insensitive (ignorecase = true); do not
attempt to synchronize symbolic links (links = false); ignore
inode number changes when detecting updates (ignoreinodenumbers =
true). Any of these change can be overridden by explicitly
setting the corresponding preference in the profile.
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 Section “Symbolic Links” in the
manual for more details. The syntax of pathspec is described in
Section “Path Specification” in the manual.
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 Section “Path
Specification” in the manual 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 synchronized depends on the preference numerids.
halfduplex
(Deprecated) When this flag is set to true, Unison network
communication is forced to be half duplex (the client and the
server never simultaneously emit data). If you experience
unstabilities with your network link, this may help.
height n
Used to set the height (in lines) of the main window in the
graphical user interface.
i Provide this preference in the command line arguments to enable
interactive profile manager in the text user interface. Currently
only profile listing and interactive selection are available.
Preferences like batch and silent remain applicable to
synchronization functionality.
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
Section “Path Specification” in the manual, and further details
on ignoring paths is found in Section “Ignoring Paths” in the
manual.
ignorearchives
When this preference is set, Unison will ignore any existing
archive files and behave as though it were being run for the
first time on these replicas. It is not a good idea to set this
option in a profile: it is intended for command-line use.
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
default, filenames are automatically taken to be case-insensitive
if either host is running Windows or OSX. In rare circumstances
it may be useful to set the flag manually.
ignoreinodenumbers
When set to true, this preference makes Unison not take advantage
of inode numbers during fast update detection. This switch should
be used with care, as it is less safe than the standard update
detection method, but it can be useful with filesystems which do
not support inode numbers.
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 manual intervention. 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 ignorenotpattern. In particular, putting
ignore = Path * in your profile and then using ignorenot to
select particular paths to be synchronized will not work.
Instead, you should use the pathpreference to choose particular
paths to synchronize.
immutable xxx
This preference specifies paths for directories whose immediate
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.
include xxx
Include preferences from a profile. include name reads the
profile “name” (or file “name” in the .unison directory if
profile “name” does not exist) and includes its contents as if it
was part of a profile or given directly on command line.
key xxx
Used in a profile to define a numeric key (0-9) that can be used
in the 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.)
links xxx
When set to true, this flag causes Unison to synchronize symbolic
links. When the flag is set to false, symbolic links will result
in an error during update detection. Ordinarily, when the flag is
set to default, symbolic links are synchronized except when one
of the hosts is running Windows. On a Windows client, Unison
makes an attempt to detect if symbolic links are supported and
allowed by user privileges. You may have to get elevated
privileges to create symbolic links.
listen xxx
When acting as a server on a TCP socket, Unison will by default
listen on any address (0.0.0.0 and [::]). This command-line
argument allows to specify a different listening address and can
be repeated to listen on multiple addresses. Listening address
can be specified as a host name or an IP address.
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 .unison directory. Set this preference if you
prefer another file. It can be a path relative to your .unison
directory. Sending SIGUSR1 will close the logfile; the logfile
will be re-opened (and created, if needed) automatically, to
allow for log rotation.
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.
maxerrors n
This preference controls after how many errors Unison aborts a
directory transfer. Setting it to a large number allows Unison to
transfer most of a directory even when some files fail to be
copied. The default is 1. If the preference is set too high,
Unison may take a long time to abort in case of repeated failures
(for instance, when the disk is full).
maxsizethreshold n
A number indicating above what filesize (in kilobytes) Unison
should flag a conflict instead of transferring the file. This
conflict remains even in the presence of force or prefer options.
A negative number will allow every transfer independently of the
size. The default is -1.
maxthreads n
This preference controls how much concurrency is allowed during
the transport phase. Normally, it should be set reasonably high
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. The
default is the special value 0, which mean 20 threads when file
content streaming is desactivated and 1000 threads when it is
activated.
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 both replicas. The syntax of pathspec -> cmd
is described in Section “Path Specification” in the manual, and
further details on Merging functions are present in Section
“Merging Conflicting Versions” in the manual.
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 Section “Mount Points and Removable Media” in the
manual.
nocreation xxx
Including the preference -nocreation root prevents Unison from
performing any file creation on root root. This preference can
be included twice, once for each root, if you want to prevent any
creation.
nocreationpartial xxx
Including the preference nocreationpartial = PATHSPEC -> root
prevents Unison from performing any file creation in PATHSPEC on
root root (see Section “Path Specification” in the manual for
more information). It is recommended to use BelowPath patterns
when selecting a directory and all its contents.
nodeletion xxx
Including the preference -nodeletion root prevents Unison from
performing any file deletion on root root. This preference can
be included twice, once for each root, if you want to prevent any
deletion.
nodeletionpartial xxx
Including the preference nodeletionpartial = PATHSPEC -> root
prevents Unison from performing any file deletion in PATHSPEC on
root root (see Section “Path Specification” in the manual for
more information). It is recommended to use BelowPath patterns
when selecting a directory and all its contents.
noupdate xxx
Including the preference -noupdate root prevents Unison from
performing any file update or deletion on root root. This
preference can be included twice, once for each root, if you want
to prevent any update.
noupdatepartial xxx
Including the preference noupdatepartial = PATHSPEC -> root
prevents Unison from performing any file update or deletion in
PATHSPEC on root root (see Section “Path Specification” in the
manual for more information). It is recommended to use BelowPath
patterns when selecting a directory and all its contents.
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 numerids.
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 interpreted 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 $-1$. If one of the replica is on a
FAT [Windows] filesystem, you should consider using the fat
preference instead of this preference. If you need Unison not to
set permissions at all, set the value of this preference to $0$
and set the preference dontchmod to true.
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, except for paths marked by the preference
merge. (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
Section “Path Specification” in the manual 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!
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. When the argument is watch,
Unison relies on an external file monitoring process to
synchronize whenever a change happens.
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 Section “Roots” in the manual. 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.
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
rootalias preference.
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.
socket xxx
Start unison as a server listening on a TCP socket (with TCP port
number as argument) or a local socket (aka Unix domain socket)
(with socket path as argument).
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 and text user
interfaces.
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 Section “Path Specification” in the manual.
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.
source xxx
Include preferences from a file. source name reads the file
“name” in the .unison directory and includes its contents as if
it was part of a profile or given directly on command line.
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. The backslash is an escape character.
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.
stream (Deprecated) When this preference is set, Unison will use an
experimental streaming protocol for transferring file contents
more efficiently. The default value is true.
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.)
unicode xxx
When set to true, this flag causes Unison to perform case
insensitive file comparisons assuming Unicode encoding. This is
the default. When the flag is set to false, a Latin 1 encoding is
assumed. When Unison runs in case sensitive mode, this flag only
makes a difference if one host is running Windows or Mac OS X.
Under Windows, the flag selects between using the Unicode or 8bit
Windows API for accessing the filesystem. Under Mac OS X, it
selects whether comparing the filenames up to decomposition, or
byte-for-byte.
version
Print the current version number and exit. (This option only
makes sense on the command line.)
watch Unison uses a file watcher process, when available, to detect
filesystem changes; this is used to speed up update detection.
Setting this flag to false disables the use of this process.
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 is true.
ROOTS
A replica’s root tells Unison where to find a set of files to be synchro-
nized, 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:// to indi-
cate that the remote server should be started with ssh(1):
ssh://remotehost//absolute/path/of/root
ssh://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
socket://[IPv6literal]:portnum/path
is used to specify the hostname and the port that the client Unison
should use to contact it. Syntax
socket://{path/of/socket}//absolute/path/of/root
socket://{path/of/socket}/relative/path/of/root
is used to specify the Unix domain socket the client Unison should use to
contact the server.
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
user ::= [-_a-zA-Z0-9]+
host ::= [-_a-zA-Z0-9.]+
| \[ [a-f0-9:.]+ zone? \] IPv6 literals (no future format).
| { [^}]+ } For Unix domain sockets only.
zone ::= %[-_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 Uni-
son 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 net-
work connection, since the full contents of every file in the remote
replica will have to be transferred to the local machine to detect up-
dates.
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 run-
ning on. The empty path (i.e., the empty sequence of names) denotes the
whole replica.
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 ex-
pressions. Each preference is associated with a list of path patterns;
the paths specified are those that match any one of the path pattern.
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, three other styles of pattern are also recognized:
Name name
matches any path in which the last component matches name,
Path path
matches exactly the path path, and
BelowPath path
matches the path path and any path below. The name and path arguments of
the latter forms of patterns are not regular expressions. Instead, stan-
dard “globbing” conventions can be used in name and path:
- a * matches any sequence of characters not including / (and not be-
ginning 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. (Be careful not to put
extra spaces after the commas: these will be interpreted literally as
part of the strings to be matched!)
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.
A path specification may be followed by the separator “ -> ” itself fol-
lowed by a string which will be associated to the matching paths:
Path path -> associated string
Not all pathspec preferences use these associated strings but all path-
spec preferences are parsed identically and the strings may be ignored.
Only the last match of the separator string on the line is used as a de-
limiter. Thus to allow a path specification to contain the separator
string, append an associated string to it, even if it is not used. The
associated string cannot contain the separator string.
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 (when using the graphical user interface; for the
text interface, you have to use the -i option). If a file named
default.prf is found, its settings will be used as the default prefer-
ences.
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 = <value>
for a preference of any other type. Whitespaces around p and the value
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.
ENVIRONMENT
UNISON 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 path for this directory. This can
be just a name, or a path. If UNISON is not defined, then the di-
rectory depends on which operating system you are using. In Unix,
the default is to use $HOME/.unison. In Windows, if the environ-
ment variable USERPROFILE is defined, then the directory will be
$USERPROFILE\.unison; otherwise, it will be c:\.unison. On
macOS, $HOME/.unison will be used if it is present, but
$HOME/Library/Application Support/Unison will be created and used
by default.
UNISONLOCALHOSTNAME
The function that finds the canonical hostname of the local host
(which is used, for example, in calculating the name of the ar-
chive 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 situ-
ations where a machine’s name changes frequently (e.g., because
it is a laptop and gets moved around a lot).
UNISONBACKUPDIR
When backups are stored centrally, the directory used to hold
them is controlled by the preference backupdir and the environ-
ment variable UNISONBACKUPDIR. If both are specified then the
environment variable overrides the preference. If neither of
these are set, then the directory $UNISON/backup is used (see en-
vironment variable UNISON above).
PAGER Used by the text interface as the pager when displaying the dif-
ferences between changed files.
NO_COLOR
If the environment variable NO_COLOR is set then Unison's text
interface will not produce any color output by default. The color
preference overrides this environment variable.
FILES
~/.unison
Unison stores a variety of information in a private directory on
each host. This is the default path of this private directory.
This path may be changed by the UNISON environment variable.
~/.unison/*.prf
Profile files. Each profile is stored in a file named
profilename.prf.
~/.unison/ar*
~/.unison/tm*
~/.unison/sc*
Main and temporary archive files. These files may be deleted if
you know what you are doing. Deleting an archive file is equiva-
lent to using the -ignorearchives option.
~/.unison/fp*
Fingerprint cache files. These files may be safely deleted. Keep
in mind that deleting a fingerprint cache file means that any
unsychronized changes must be scanned again. Depending on your
replicas, this may mean scanning gigabytes of file contents.
~/.unison/lk*
Lock files indicating a running Unison process. These files may
be deleted if you are careful and know that there is no Unison
process currently running. Deleting a lock file is equivalent to
using the -ignorelocks option.
EXAMPLES
Synchronize two local directories
unison path/to/dir1 /dir2
This command synchronizes two local directories using the default op-
tions. Default options are defined by Unison and can be overridden by
user in a profile called “default”, which is by default stored in file
~/.unison/default.prf
Synchronize a local and a remote directory
unison local/dir ssh://user@host//absolute/path
This command synchronizes a local directory (here specified by a rela-
tive path) and a remote directory (here specified by an absolute path)
using ssh(1) and the default options (see example above).
Synchronize with all options specified in a profile
unison profilename
This command reads all the options from the profile named “profilename”
and synchronizes according to those options.
Synchronize with options specified in a profile and roots on command line
unison profilename /path/to/dir ssh://host/path/on/server
This command reads all options from the profile named “profilename”
with only the roots specified on the command line. Roots must not be
specified in the profile as the roots from command line will not over-
ride roots in the profile, rather append to the list of roots.
Synchronize automatically
unison -batch /path/to/dir ssh://host/path/on/server
This command synchronizes all non-conflicting changes automatically,
once.
Synchronize continuously
unison -repeat watch /path/to/dir ssh://host/path/on/server
This command first fully synchronizes the roots and then remains dor-
mant, waiting for any file changes within either root and then automat-
ically synchronizes these changes. This also works in a profile (repeat
= watch). If the filesystem monitoring helper program is not available
or not desired for other reasons, it is possible to make Unison syn-
chronize repeatedly with a defined time interval:
unison -repeat 60 /path/to/dir ssh://host/path/on/server
This command synchronizes every 60 seconds. Using -repeat implies
-batch.
Currently, continuous synchronization is not possible when using the
GUI.
DIAGNOSTICS
When running in the textual mode, Unison returns an exit status, which
describes whether, and at which level, the synchronization was success-
ful. 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.
COMPATIBILITY
If you are using Unison versions ≥ 2.52 on all machines, you do not have
to do anything extra for compatibility.
Historically (versions < 2.52), Unison versions had to be matched rela-
tively exactly for them to work together. Additionally, the version of
compiler used to build Unison also had significant relevance for compati-
bility.
As of version 2.52, Unison has a degree of backward and forward compati-
bility. This means three things. First, it is possible for local and re-
mote machines to run a different version of Unison. Second, it is possi-
ble for local and remote machines to run a version (same or different) of
Unison built with a different version of compiler. Lastly, it is possible
to upgrade Unison on the local machine and keep the existing archive.
For more information on co-existence of versions < 2.52 and ≥ 2.52, see
https://github.com/bcpierce00/unison/wiki/2.52-Migration-Guide
SEE ALSO
There is a full user manual (pdf, html and txt) included with Unison and
available online. Depending on your operating system, this manual may
have been installed at /usr/share/doc/unison/ or a similar location. The
manual can also be read in the GUI (look in the Help menu) or on the com-
mand line by unison -doc all (you probably want to pipe the output to a
pager).
https://github.com/bcpierce00/unison
https://www.cis.upenn.edu/~bcpierce/unison/
unison March 17, 2022 unison
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