We have been really busy the last year or so, so it has been a really loooong time since we posted regularly.
We promisse to try and post more regularly, once every week or so…

Hope you enjoy!

As opposed to rsync, unison is a two way file synchronizer. Similar to MySQL’s master to master replication. To set it up in Ubuntu (Intrepid) keep on reading…

1. Install unison on both servers

apt-get install unison

2. Create a script to add to crontab to call unison periodically

unison -numericids -owner -silent -times -contactquietly -batch -auto -log -logfile /var/log/unison.log profile_file 2>&1

3. Create the above mentioned profile file on ~/.unison/profile_file.prf

root = ssh://server_ip//path/to/root/dir
root = /path/to/root/dir
ignore = Regex .*(cache|Cache|te?mp|logs?).* # ignore log and cache files

That’s it! Now add the following line to your crontab to execute it every 5min

*/5 * * * * /path/to/my_unison_script.sh

After a few days of running this I found that sometimes one unison execution would overlap another. To resolve this I found a little tool called lockrun

To get it to work I did:

1. Download the source code from the official lockrun website

wget http://unixwiz.net/tools/lockrun.c

2. Build/install as shown in http://unixwiz.net/tools/lockrun.html

gcc lockrun.c -o lockrun
sudo cp lockrun /usr/local/bin/

3. Change the previous crontab line to use lockrun

*/5 * * * * /usr/local/bin/lockrun --lockfile=/tmp/hosting.lockrun -- /path/to/my_unison_script.sh

All done!!!

In order to keep my servers always showing the correct date/time I use a little software called chrony and make sure I’m using the correct time zone.

All the actions below need superuser privileges

To install it simply use apt-get:

$ apt-get install chrony

Once you’ve installed chrony you need to select your current time zone:

$ tzselect

To make sure it is selected on every boot I just export the TZ environment variable in my /etc/rc.local

$ vi /etc/rc.local

And add the following lines:
# Export timezone
TZ=’Europe/Brussels’; export TZ

I found doing the above was not enough, so I also edited my /etc/timezone file and added the correct time zone there:

$ echo "Europe/Brussels" > /etc/timezone

And still it wasn’t enough, so I reconfigured the package tzdata

$ dpkg-reconfigure tzdata

And finally that did it! To make sure it would still be correct on a future reboot I rebooted my machine:

$ reboot