A simple backup scheme using rsnapshot

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This article describes a simple automated backup scheme using the tool rsnapshot, which is based on rsync. rsnapshot makes a specified number of incremental backups of specified file trees, using hard links to save space on the backup medium.

The following backup scheme will rotate the backups on a daily, weekly and monthly basis. That means, it will keep a daily snapshot for 7 days, a weekly snapshot for 4 weeks and a monthly snapshot for 12 month. Furthermore, it uses an extra partition for the backup which will be mounted only for the time of the backup process.



Install app-backup/rsnapshot:

root #emerge --ask app-backup/rsnapshot



Assumed the backup partition is labeled backup, formatted with ext4 and it should be mounted on /mnt/backup during backup: Add an entry like the following in your fstab:

FILE /etc/fstab
LABEL=backup    /mnt/backup    ext4    noatime,noauto    0 0

The noauto option means that this backup filesystem will not be mounted by default. The backup filesystem would normally be on an external device to be safe in the case of a device failure.

Cron scripts

Create cron scripts for the different backup intervals:

FILE /etc/cron.daily/rsnapshot.daily
echo "### RSNAPSHOT DAILY ###"
mount /mnt/backup && rsnapshot daily || echo "Backup failure"
umount /mnt/backup
echo ""
FILE /etc/cron.weekly/rsnapshot.weekly
echo "### RSNAPSHOT WEEKLY ###"
mount /mnt/backup && rsnapshot weekly || echo "Backup failure"
umount /mnt/backup
echo ""
FILE /etc/cron.monthly/rsnapshot.monthly
echo "### RSNAPSHOT MONTHLY ###"
mount /mnt/backup && rsnapshot monthly || echo "Backup failure"
umount /mnt/backup
echo ""
These scripts must be executable before they will run.
rsnapshot knows nothing about timing. The daily, weekly and monthly parameters are identifiers for rsnapshot without any semantic meaning. Therefore, it is important to call the daily snapshot only once a day, to call the weekly snapshot only once a week, etc.

rsnapshot configuration files

Set up the rsnapshot configuration file.

rsnapshot configuration files are tab delimited. Be careful to always use tabs instead of spaces for the options.
Filetree specifications are in rsync format. See the rsync man page for details.

Default rsnapshot config file:

FILE /etc/rsnapshot.conf
# Default config version
config_version	1.2

# So the hard disk is not polluted in case the backup filesystem is not available
no_create_root	1

# Standard settings
cmd_cp			/bin/cp
cmd_rm			/bin/rm
cmd_rsync		/usr/bin/rsync
link_dest		1

# For convenience, so that mount points can be taken as backup starting points
one_fs			1

# Store all backups in one directory per machine
# A useful alternative may be to create a separate directory for each interval
snapshot_root	/mnt/backup/

# increments, which are kept
retain	daily	7
retain	weekly	4
retain	monthly	12

# Backup folder(s)/files
backup	/path/to/something/	localhost/
backup	/var/			localhost/

# Exclude pattern (refer to --exclude-from from rsync man page)
exclude		/path/to/something/tmp/

In these files, the second argument of backup specifies a container directory for the backups, usually referring to the machine (in this case, localhost). This can be changed to any name of your choosing. The final snapshots will be saved under /mnt/backup/{daily,weekly,monthly}.[0-9]*/localhost/path/to/something/

rsnapshot will always take the last daily snapshot to create the first weekly snapshop and the last weekly snapshot to create the first monthly one. It will not take the 7th daily snapshot to create the first weekly snapshot. Therefore, it is possible to keep less or more than 7 daily snapshots, but is this case the first weekly snapshot is not one week old.

Using rsyncd on a trusted LAN

Following the Home Router Rsync server you can setup a rsync daemon on your source computer with a share like:

FILE /etc/rsyncd.conf
  path = /home/larry
  comment = Larry's home directory
  exclude = /foo

On the destination server, which runs rsnapshot, define a backup line in /etc/rsnapshot.conf like:

FILE /etc/rsnapshot.conf
backup	larry@my_computer::larry	larry/

Pay attention to highly insecure mechanism without password checking or encrypted transfer.



To restore the localhost backups specified above, we would use:

root #mount /mnt/backup
root #rsync -a /mnt/backup/localhost/monthly.0/localhost/. /mnt/myroot/
root #rsync -a /mnt/backup/localhost/weekly.0/localhost/. /mnt/myroot/
root #rsync -a /mnt/backup/localhost/daily.0/localhost/. /mnt/myroot/

where /mnt/myroot is the mount point of the fresh root filesystem. In the paths above *.0 refers to the latest increment.

Possible improvements

It is also possible to make remote backups via rsync or SSH -- see the rsnapshot man page for details.

BTRFS snapshots

Those using btrfs can leverage its snapshotting abilities with rsnapshot. Walter Werther has a guide on this.