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Simple script to backup a Citrix XenServer system

branch: master
README
Xenserver snapshot and template based backup script
https://github.com/markround/XenServer-snapshot-backup
Mark Round, github@markround.com

This README was copied from the text at http://www.markround.com/snapback

Please visit this page for the full HTML version of the README, along with
screenshots which may make this a little clearer!

We have recently started using Citrix Xenserver in
production at work (fantastic product, see my review at
http://www.markround.com/archives/63-Citrix-XenServer-5.6-Review.html for
more information) and needed a simple backup solution. Our VMs run from an
iSCSI SAN and are backed up daily through various methods - e.g. Bacula for
the Unix/Linux systems. However, we wanted the ability to quickly roll back
to a previous VM snapshot, and get up and running quickly if our SAN failed
for whatever reason.

Our solution was to create a large shared NFS storage repository, and
periodically snapshot VMs and copy the templates over to this SR. Doing
this means that if the SAN fails, we can create a new VM quickly from this
NFS store (using the Xenserver's local disks, or even the NFS SR itself as
storage). Once up and running, we can bring VMs back up to date by restoring
the latest backup to them.

In order to automate this, I wrote a quick script which I thought may prove
useful to someone else, so decided to post it here.

It is very simple, and although it may serve well as your only backup
solution, it's really intended as an image-level compliment to your primary
file-system based backup system such as Bacula, Amanda, Netbackup etc. It
also has not had much testing, and I fully appreciate the scripting is pretty
rudimentary and could do with some optimisation - there's no error checking,
for instance. I kept it pretty verbose on purpose though, so you can get a
good idea of exactly what it's doing at each step; it may be better to think
of this as a template you can base your own scripts off!

* Note * There is now a snapback-xva.sh script, which has modifications by 
Luis Davim, which support the creation of additional XVA snapshots on
an independant schedule. This is a great addition to the script, but as it
may not be suitable for all users, it's included as a separate script.
Thanks, Luis!

Overview
========

The script creates a snapshot of a running VM on a configurable schedule,
and then creates a template from this snapshot. It will copy all these
backup templates over to a configurable storage repository, and then clean
up any old backups according to a specified retention policy. These backups
are full backups, so if you have a 10GB VM and keep 7 previous copies you
will need a total of 80GB disk space on your backup VM. Non-running VMs,
and those not configured (as detailed below) will be skipped.

Important: See http://support.citrix.com/article/CTX123400. After backing
up each VM, you will end up with a new VDI, so you may need to manually
coalesce your VDIs again to reclaim disk space. This appears to have been
fixed in 5.6FP1, however.

Installation and usage
=====================

First, copy the script to your Xenserver pool master, and make it executable. A
good location for this is

/usr/local/bin/snapback.sh.

Next, create a cron entry for the script - to make it run daily just after
1AM, you'd create /etc/cron.d/backup with the following contents :

2 1 * * * root /usr/local/bin/snapback.sh > /var/log/snapback.log 2>&1

This will also record a log of it's actions to /var/log/snapback.log. You
now need to edit the script and change the DEST_SR variable to the UUID
of your backup storage repository. You can find this value by clicking
on the SR in Xencenter; the UUID will be displayed as a value like
"2c01dc26-f525-70d6-dedf-00baaec76645".

Lastly, you need to configure your backup and retention policy for your VMs. In
Xencenter, right click your VM, and select "Properties". Click on "Custom
Fields", and then "Edit Custom Fields". You should add two text fields :


backup : Can be one of "daily", "weekly", or "monthly". If it is set to
weekly, it will by default run on a Sunday, and if it set to monthly, it
will run on the first Sunday of the month. This day can be changed at the
top of the script - see the WEEKLY_ON and MONTHLY_ON variables.

retain : How many previous backups (in addition to the currently running
backup) to keep. So, setting this to a value of "2" would mean that after
a backup has run, you would end up with 3 backups in total.


The script will look for these fields when it is run, and will skip any VM
that doesn't have them set. You can also see them in the Xencenter summary
and properties for the VM.

You can now either run the script manually, or wait until the cron job
kicks off. It will produce a detailed log to the console (or log file if
run through cron), and when it's finished, you'll see your template backup
VMs listed in Xencenter.

If you find that this clutters up the Xencenter view a little, you can always
hide them (View->Server View->Custom Templates).

To restore a VM from a backup, just right click, and choose "New template
from backup". Anyway, I hope this helps someone else!

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