Unison

References

• Homepage
• Manual
  • Unison manual is usually found locally at /usr/share/doc/unison*/.
  • Sample Profiles
• Unison: Backup & synchronize files

Unison also has built-in help:

unison -help               # Brief help
unison -doc topics         # Get list of details documentation
unison -doc all            # Get the whole manual

Alternatives to Unison

• SyncThing (link fails in Opera)
• Bit-torrent Sync (see this tutorial)

Basic usage

• Synchronize two directories

unison <dir-a> <dir-b>

• Selecting files to synchronize
  • Synchronize home directory, using Ignore facility to skip some files.
  • Create a subdirectory called shared, and synchronize that directory only.
  • (Linux only) Create a subdirectory called shared, with symbolic links to other local directories, and synchronize that directory only using follow (making symlink transparent).
  • Synchronize home directory as root, using -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.

Configuration tips

• On Samba / CIFS file system, ignore permissions:

perms = 0

In some cases, you also need to use the preferences dontchmod.

• When running unison with ssh, uses servercmd if unison is not found in the path:

servercmd = /usr/bin/unison

Basic Profile

Here we assume that all profiles will include the default one. If not, a more complex solution is to create a file .unison/common-prefs, that would be included by all profiles, including the default one.

Here a basic setup to backup pen usb stick on Cygwin:

~/.unison/default.prf (<file name="default.prf" tag="source">download</file>)

# Unison default preferences file

# Fastcheck - by default false on windows machine, and true on Unix machine.
# When true, uses modification date + file size as inone number. Otherwise do a full scan
fastcheck = true

# If any new preferences are added by Unison (e.g. 'ignore'
# preferences added via the graphical UI), then store them in the
# default profile file
addprefsto = default.prf

# Ignore file permissions (necessary on samba/CIFS fs)
perms = 0

# Make sure that both roots are mounted
mountpoint = .

# Common Ignore specification
ignore = Name System Volume Information

~/.unison/usb-pen-backup.prf (<file name="usb-pen-backup.prf" tag="source">download</file>)

# Roots of the synchronization
root = /cygdrive/f
root = /cygdrive/z

# Common include
include default.prf