Full system backup with rsync

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Revision as of 21:01, 13 January 2014 by FSMaxB (Talk | contribs) (replaced the --exclude flag with the much cleaner -x that only copies files on the root filesystem)

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This article is about using rsync to transfer a copy of your "/" tree, excluding a few select folders. This approach is considered to be better than disk cloning with dd since it allows for a different size, partition table and filesystem to be used, and better than copying with cp -a as well, because it allows greater control over file permissions, attributes, Access Control Lists (ACLs) and extended attributes. [1]

Either method will work even 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.

With a single command

As root, run:

# rsync -aAXvx /* /path/to/backup/folder
Note: If you are heavy user of hardlinks, you might consider using additionally -H rsync's option, which by default is turned off as memory expensive during rsync run, but nowadays it should be no problem on most of modern machines. There are a lot of hard links below the /usr folder which save disk space.
Note: You may want to add rsync's --delete option if you are running this multiple times to the same backup folder

Using a script

Same as in the above method, the system files are transferred in archive mode, ensuring that symbolic links, devices, permissions and ownerships, among other file attributes are preserved. On top of that, it shows at the end how much time it took, and it also writes a blank file stating when the backup was created. To learn more about what this script does, read man rsync and man date.

Note: You may want to add rsync's --delete option if you are running this multiple times to the same backup folder
$ cd ~/Scripts
$ nano backup.sh

if [ $# -lt 1 ]; then 
    echo "No destination defined. Usage: $0 destination" >&2
    exit 1
elif [ $# -gt 1 ]; then
    echo "Too many arguments. Usage: $0 destination" >&2
    exit 1
elif [ ! -d "$1" ]; then
   echo "Invalid path: $1" >&2
   exit 1
elif [ ! -w "$1" ]; then
   echo "Directory not writable: $1" >&2
   exit 1

case "$1" in
  "/mnt") ;;
  "/mnt/"*) ;;
  "/media") ;;
  "/media/"*) ;;
  *) echo "Destination not allowed." >&2 
     exit 1 

START=$(date +%s)
rsync -aAXvx /* $1
FINISH=$(date +%s)
echo "total time: $(( ($FINISH-$START) / 60 )) minutes, $(( ($FINISH-$START) % 60 )) seconds" | tee $1/"Backup from $(date '+%A, %d %B %Y, %T')"
$ chmod +x backup.sh

Backing up is easy.

While the system is running, open up a terminal and run (as root):

# /home/user/Scripts/backup.sh /some/destination

(replace user with username since you created the directory as user in the user's home directory)

You can also replace both $1 instances from the script with the actual destination path, move it to one of the folders from echo $PATH, and then simply run (as root):

# backup.sh

Boot requirements

Having a bootable backup can be useful in case the filesystem becomes corrupt or if an update breaks the system. The backup can also be used as a test bed for updates, with the [testing] repo enabled, etc. If you transferred the system to a different partition or drive and you want to boot it, the process is as simple as updating the backup's /etc/fstab and your bootloader's configuration file.

Update the fstab

Without rebooting, edit the backup's fstab to reflect the changes:

# nano /path/to/backup/etc/fstab
tmpfs        /tmp          tmpfs     nodev,nosuid             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 booting the backup will fail. In this example, all of the offending entries are replaced with a single one:

# nano /path/to/backup/etc/fstab
tmpfs        /tmp          tmpfs     nodev,nosuid             0   0

/dev/sdb1    /             ext4      defaults                 0   1

Remember to use the proper device name and filesystem type.

Update the bootloader's configuration file

This section assumes that you backed up the system to another drive or partition, that your current bootloader is working fine, and that you want to boot from the backup as well.

For Syslinux, all you need to do is duplicate the current entry, except pointing to a different drive or partition:

Tip: Instead of editing syslinux.cfg, you can also temporarily edit the menu during boot. When the menu shows up, press the Tab key and change the relevant entries. Partitions are counted from one, drives are counted from zero.
# nano /boot/syslinux/syslinux.cfg

For GRUB, it's recommended that you automatically re-generate the grub.cfg file:

# pacman -S os-prober
# grub-mkconfig -o /boot/grub/grub.cfg

Also verify the new menu entry in /boot/grub/grub.cfg. Make sure the UUID is matching the good partition, or else it could still boot on the old system.

First boot

Reboot the computer and select the right entry in the bootloader. This will load the system for the first time. All peripherals should be detected and the empty folders in / will be populated.

Now you can re-edit /etc/fstab to add the previously removed partitions and mount points.

If you transferred the data from HDD to SSD (solid state drive), don't forget to activate TRIM. Also consider using HDD and tmpfs mount points to reduce SSD wearing - see Relocate files to tmpfs and Tips for Minimizing SSD Read & Writes.

Note: You may have to reboot again in order to get all services and daemons working correctly. Personally, pulseaudio would not initialise because of a module loading error. I restarted the dbus.service to make it work.

See also

  1. Howto – local and remote snapshot backup using rsync with hard links Includes file deduplication with hard-links, MD5 integrity signature, 'chattr' protection, filter rules, disk quota, retention policy with exponential distribution (backups rotation while saving more recent backups than older)