This HOWTO shows you how to setup the Unison file synchronizer to backup files from one server to another.
Topics include:

1. The options I use in a Unison profile
2. Setup of a simple shell script so you can automate the process

Get unison from here.
For more info on unison go to : http://www.cis.upenn.edu/~bcpierce/unison/

Here's HOWTO of how to setup UNISON on a Windows box: \\http://www.cis.upenn.edu/~bcpierce/unison/download/releases/stable/unison-manual.html#ssh-win

Create a Unison profile
####################
# Now create a Unison profile

cd /home/unison/.unison
edt sync_server.prf

# Here's my profile. Read comments and change to suit your needs

#---- Start of File ----#
###########################################
# #
# /home/unison/.unison/sync_server.prf #
# unison configuration file #
# Author: Brynn Neilson #
# Email: admin@spinning-planet.com #
# Date: 12 September 2004 #
# #
###########################################

# Roots of the synchronization
root = /
root = socket://[ip of your master server]:PORT

# Where PORT is the port on which the server is listening on.

# Don't ask questions. Just do the sync
batch = true

# Automatically choose default solution
auto = true

# syncronize owner info
owner = true

# syncronize super duper deluxo hybird nano technology group maximus highness deluxe edition
group = true

# syncronize modification times
# times = true

# force to write over old files
# force = ssh://[ip of your master server]//
# force = newer

# suppress status messages
# terse = true

## Paths to synchronize
# path = current
path = etc/passwd
path = etc/group
path = etc/exim.conf
path = etc/aliases
path = home
path = pkg
path = usr

# Some regexps specifying names and paths to ignore
ignore = Name temp.*
ignore = Name *~
ignore = Name .*~
ignore = Name *.o
ignore = Name *.tmp
ignore = Name server.crt
ignore = Name server.key
ignore = Name pass.key
ignore = Name local-host-names
# ignore = Name e107_stat*
# ignore = Name e107_online*
# ignore = Path home/sites/spinningplanet
# ignore = Path = var/lib/mysql/spinningplanet
# following pattern will make Unison ignore any path containing the name
# ignore = Name {statistics,spamassassin,stats,cache,.razor,.imap.index,razor-agent.log,dovecot-uidlist,access_log,e
rror_log}
ignore = Name {imdb}

# Window height
# height = 37
## Keep a backup copy of the entire replica
# backup = Name *

# Use this command for displaying diffs
# diff = diff -y -W 79 --suppress-common-lines

# Log actions to the terminal
log = true
#---- End of File ----#

Create a shell script to run unison. You can actually test Unison first by typing:

unison sync_servers.prf

# add something like this:

#---- Start of File ----#
#################################
# Author: Brynn Neilson
# Date: Sunday, October 3rd. 2004
#
# This is the Syncronization script to sync ns2.spinning-planet.com and #
# ns3.spinniing-planet.com
#
#################################

# Stop Apache, cop etc files, and restart pointing at an offline html
# page to allow MySQL to be stopped so it can be copied

# Copyimg etc to backup folder /etc_backup so I have a local backup

unison /etc /etc_backup -force /etc -batch -group -owner

# I need to stop apache and restart with a temprary page

httpd -k stop
httpd -f /etc/httpd/conf/offline-httpd.conf

# Need to stop mysql because it will corrupt if it is running when copied

service mysqld stop

# make local backup of mysql DBs

unison /var/lib/mysql /var/lib/mysql_backup -force /var/lib/mysql -batch -group -owner

# Do the same on master server

ssh [ip of master server] unison /etc /etc_backup -force /etc -batch -group -owner
ssh ns3.spinning-planet.com service mysqld stop
ssh ns3.spinning-planet.com httpd -k stop
ssh ns3.spinning-planet.com httpd -f /etc/httpd/conf/offline-httpd.conf
ssh ns3.spinning-planet.com unison /var/lib/mysql /var/lib/mysql_backup -force /var/lib/mysql -batch -group -owner

# now sync both servers

unison sync_all.prf

# restart everything back to normal on both servers

ssh ns3.spinning-planet.com service named restart
ssh ns3.spinning-planet.com service mysqld start
ssh ns3.spinning-planet.com httpd -k stop
ssh ns3.spinning-planet.com httpd -f /etc/httpd/conf/httpd.conf
service named restart
service mysqld start
httpd -k stop
httpd -f /etc/httpd/conf/httpd.conf
#-- End of file --#

Of course your script doesn't have to have as much stuff in it but you will need to stop any databases that are running or they will get corrupt

# Make script executable

chmod 755 sync_servers.sh

# test it

./sync_servers.sh

If it all works all you need to do is create a cron job to run it. You can create different unison profiles to backup daily, weekly, or just specific user data if you want. There is also a binary for windows. Don't use the windows gui though. Create a unison profile instead. When you install it on windows just look for a file called default.prf. Also note that the windows user can only backup data for the same name user on the linux box.

If you have any questions feel free to contact me

brynn

See also for win config http://www.minezone.org/wiki/MVance/FileSyncingHowTo