System backup

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Revision as of 10:33, 8 July 2012 by DSpider (talk | contribs) (Backup script: a few cosmetic changes)
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This rsync script allows creating a full backup copy across filesystems. It is setup so that the copy includes intact booting capabilities, optionally excluding selected files.

The approach has benefits over omitting system files by just copying personal data; if the system becomes corrupted in the main partition, overcoming the problem means booting into the backup as opposed to identifying and reinstalling affected programs.

Instructions were converted from this forum post.

With a single command

This operation can be done while the system is running. Since it's going to take a while, you may freely browse the web during this time. Worst case scenario you won't get the same opened tabs when you restore the backup (or boot from it) because they weren't saved. Not a big deal.

As root, run:

Warning: If you plan on backing up your system somewhere other than /mnt or /media, don't forget to add it to the list, to avoid a copying loop.
# rsync -av /* /media/Backup/backup --exclude={/dev/*,/proc/*,/sys/*,/tmp/*,/run/*,/mnt/*,/media/*,/lost+found,$HOME/.gvfs}
Note: The contents of /dev, /proc, /sys, /tmp, /run were excluded because they are populated at boot (while the folders themselves are not created), lost+found is filesystem-specific, and $HOME/.gvfs should be added too, so that it won't complain at the end that "some files/attrs were not transferred".
Note: Additionally, you may also want to skip ~/.thumbnails/*, ~/.mozilla/firefox/*.default/Cache/* and ~/.cache/chromium/*

With a list

For this method, two files are needed: the backup script and a file stating which files to include/exclude from the backup source.

Backup script

The script is very simple; it rsyncs in archive mode, ensuring that symbolic links, devices, permissions and ownerships, among other file attributes are preserved, while excluding files that match the patterns from the include/exclude list.

Save it as and make it executable:

sudo sh -c "
    rsync -av --delete-excluded --exclude-from=backup.lst / $1;
    date > $1/BACKUP
Backup source: /
In this case it's performing a backup on the whole root.
Backup destination: $1
Passed as an argument to the script (e.g. /media/backup)
Exclude list: --exclude-from=backup.lst
This example uses a file called backup.lst.

Exclude list

As deciding which files should populate this list can be difficult, here's a typical example of files that do not need to be backed up.

Save the following as backup.lst:

# Include

# Commented out. See bellow.

# Exclude
- /dev/*
- /run/*
- /proc/*
- /sys/*
- /tmp/*
- lost+found/
- /media/*
- /mnt/*
Warning: don't forget to also exclude the mounted directory where you'll put the backup to avoid an infinite loop. You can use some folder in /media or /mnt, since they're already on the list.
Content in system directories; /dev, /proc, /sys and /tmp are excluded because they are created by the system at runtime, while the directories themselves need to be preserved since they are not regenerated at boot. Lastly, all lost+found instances are skipped since they are partition-specific. For Archlinux /var/lib/pacman/sync/* can also be excluded. This can save a lot of time on every backup since the directory contains many small files that tend to change quite often. These are description files for every package from the repositories. These files can be regenerated with pacman -Syu.
See the example at the bottom of this article if you explicitly want to keep something from the user folder or /media (although you could simply copy them after rsync is done, so this section is a bit redundant). Note that specifying every desired file or directory in Include is not needed; this section only acts as a filter for statements in Exclude.

Backing up

Substitute /media/backup as appropriate, and mount the destination device:

# mount /dev/sdb1 /media/backup
Tip: if the ability to boot the backup isn't important, omit the previous step and simply backup to an arbitrary directory.

Run the backup script (note that the trailing "/" character is necessary):

# ./ /media/backup/

Boot setup

After the sync is finished, the backup destination's /etc/fstab has to be modified, a boot loader needs to be installed on the backup destination, and configuration in the destination's /boot/grub/menu.lst requires to reflect the new location.

Modify fstab

Edit the backup destination's fstab:

# nano /media/backup/etc/fstab
tmpfs        /tmp          tmpfs     nodev,nosuid,noexec      0   0

/dev/sda1    /boot         ext2      defaults                 0   2
/dev/sda5    none          swap      defaults                 0   0
/dev/sda6    /             ext4      defaults                 0   1
/dev/sda7    /home         ext4      defaults                 0   2

Because rsync has performed a recursive copy of the entire root filesystem, all of the sda mountpoints are problematic and will cause the backup boot to fail. In this example, all of the offending entries are replaced with a single one:

# nano /media/backup/etc/fstab
tmpfs        /tmp          tmpfs     nodev,nosuid,noexec      0   0

/dev/sdb1    /             ext4      defaults                 0   1

Remember to use the proper device name and filesystem type.

Install bootloader

While these instructions assume GRUB is being employed, they could easily be adapted to other bootloaders, such as LILO.

Open the GRUB console:

# grub

Direct the install towards the destination device:

root (hd1,0)
setup (hd1)
root; hd 1,0
This should point to where the GRUB files are located--in this case, "hd 1" means the second storage device (/dev/sdb) and "0" is the first partition (/dev/sdb1).
setup; hd 1
The command specifies where the actual boot loader is to be installed. In this example it is installed to the MBR of the second storage device.

Configure bootloader

The problem here is that even though the boot loader installs correctly, its menu entries are for the main system's partitions, not the backup system's.

It's possible to fix this by creating a custom /boot/grub/menu.lst for the backup destination. In order to do this, modify so that it copies a custom menu.lst:
# rsync backup script

sudo sh -c "
    rsync -av --delete-excluded --exclude-from=backup.lst / $1;
    cp ~/ $1/boot/grub/menu.lst;
    date > $1/BACKUP
Tip: instead of replacing menu.lst with a custom version solely for the backup, add a new GRUB entry pointing to the backup device or simply edit GRUB's menu during boot time.

External links

A sample implementation can be found here: