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# System backup

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Related articles

- Synchronization and backup programs
- System maintenance#Backup
- Data-at-rest encryption#Backup for disk encryption scenarios
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A system backup is the process of backing up the operating system, files and system-specific useful/essential data. [It] primarily ensures that not only the user data in a system is saved, but also the system's state or operational condition. This helps in restoring the system to the last-saved state along with all the selected backup data.[1]

## Using Btrfs snapshots

See Btrfs#Snapshots, #Snapshots and /boot partition, and Snapper.

## Using LVM snapshots

See LVM#Snapshots, Create root filesystem snapshots with LVM, and #Snapshots and /boot partition.

## Using rsync

See rsync#As a backup utility.

## Using tar

See Full system backup with tar.

## Using SquashFS

See Full system backup with SquashFS.

Note: SquashFS does not support ACLs.

## Bootable backup

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 boot loader's configuration file.

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

### Update the fstab

Without rebooting, edit the backup's fstab by commenting out or removing any existing entries. Add one entry for the partition containing the backup like the example here:

    /dev/sdaX    /             ext4      defaults                 0   1

Remember to use the proper device name and filesystem type.

### Update the boot loader's configuration file

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.

For GRUB, it is recommended that you automatically re-generate the main configuration file. If you want to freshly install all GRUB files to somewhere other than `/boot`, such as `/mnt/newroot/boot`, use the `--boot-directory` flag.

Also verify the new menu entry in `/boot/grub/grub.cfg`. Make sure the UUID is matching the new partition, otherwise it could still boot the old system. Find the UUID of a partition with lsblk:

    $ lsblk -no NAME,UUID /dev/sdXY

where `/dev/sdXY` is the desired partition (e.g. `/dev/sdb3`). To list the UUIDs of partitions GRUB thinks it can boot, use grep:

    # grep UUID= /boot/grub/grub.cfg

### First boot

Reboot the computer and select the right entry in the boot loader. 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.

## Snapshots and /boot partition

The factual accuracy of this article or section is disputed.

Reason: "the vmlinuz and other essential files effectively are deleted before this hook runs". (Discuss in Talk:System backup#Snapshots and /boot partition hook is broken)

If your file system supports snapshots (e.g., LVM or Btrfs), these will most likely exclude the `/boot` partition or ESP.

You can copy the boot partition automatically on a kernel update to your `root` partition with a pacman hook (make sure the hook file is owned by root):

    /etc/pacman.d/hooks/95-bootbackup_pre.hook

    [Trigger]
    Operation = Upgrade
    Operation = Install
    Operation = Remove
    Type = Path
    Target = usr/lib/modules/*/vmlinuz

    [Action]
    Depends = rsync
    Description = Backing up pre /boot...
    When = PreTransaction
    Exec = /usr/bin/bash -c 'rsync -a --mkpath --delete /boot/ "/.bootbackup/$(date +%Y_%m_%d_%H.%M.%S)_pre"/'

    /etc/pacman.d/hooks/95-bootbackup_post.hook

    [Trigger]
    Operation = Upgrade
    Operation = Install
    Operation = Remove
    Type = Path
    Target = usr/lib/modules/*/vmlinuz

    [Action]
    Depends = rsync
    Description = Backing up post /boot...
    When = PostTransaction
    Exec = /usr/bin/bash -c 'rsync -a --mkpath --delete /boot/ "/.bootbackup/$(date +%Y_%m_%d_%H.%M.%S)_post"/'

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- Backup

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