Rsync Backup root filesystem
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.
Files
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
rbackup.sh and make it executable:
rbackup.sh
#!/bin/sh
# rsync backup script
sudo sh -c "
rsync -av --delete-excluded --exclude-from=backup.lst / $1;
touch $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
- Include/exclude list; --exclude-from=backup.lst
- This example uses backup.lst.
Include/exclude list
As deciding which files should populate this list can be difficult,
here's a typical backup example that excludes common files that do not
need to be backed up, such as the vast majority of
/dev. Note that specifying every desired file or directory in
Include is not needed; this section only acts as a filter for statements in
Exclude. This file is in the traditional include/exclude rsync format.
Save the following as
backup.lst:
backup.lst
# Include
+ /dev/console
+ /dev/initctl
+ /dev/null
+ /dev/zero
# Exclude
- /dev/*
- /proc/*
- /sys/*
- /tmp/*
- lost+found/
- /media/backup/*
- Exclude
- 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.
Warning: don't forget to also exclude the mounted directory where you'll put the backup to avoid an infinite loop (in this example /media/backup/).
- Include
- Even though /dev is excluded, 4 files that are not dynamically created by udev need to be preserved. These are console, initctl, null and zero.
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):
# ./rbackup.sh /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
none /dev/pts devpts defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/sda1 /boot ext4 defaults 0 1
/dev/sda5 /var ext4 defaults 0 1
/dev/sda6 /usr ext4 defaults 0 1
/dev/sda7 / ext4 defaults 0 1
/dev/sda8 /home ext4 defaults 0 1
/dev/sda9 swap swap defaults 0 0
Because rsync has performed a recursive copy of the
entire root filesystem, all of the
sda
mounpoints 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
none /dev/pts devpts defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/sdb1 / ext4 defaults 0 1
As before, 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
rbackup.sh so that it copies a custom
menu.lst:
rbackup.sh
#!/bin/sh
# rsync backup script
sudo sh -c "
rsync -av --delete-excluded --exclude-from=backup.lst / $1;
cp ~/custom.menu.lst $1/boot/grub/menu.lst;
touch $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.
References:
https://wiki.archlinux.org/index.php/Full_System_Backup_with_rsync
