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Full operating-system tar backup of a Linux server

A simple bare-bones backup: one compressed tarball of the whole root filesystem, minus the folders that are virtual, temporary or backed up separately.

Exclude list

/etc/backup.exclude:

/proc/*
/sys/*
/dev/*
/run/*
/tmp/*
/var/tmp/*
/usr/tmp/*
/mnt/*
/media/*
/lost+found
/var/cache/*
/swapfile

Keep /etc/fstab in the backup; you will want it for a restore.

The backup

#!/bin/bash
set -euo pipefail
umask 077                                  # the archive contains /etc/shadow and keys
dst=/mnt/backup/$(hostname -s)/system
mountpoint -q /mnt/backup
mkdir -p "$dst"
nice -n 19 tar --one-file-system -cpjf "$dst/$(date +%F).system.tar.bz2" \
    --exclude-from=/etc/backup.exclude -C / .
find "$dst" -type f -name '*.tar.bz2' -mtime +3 -delete
  • Use --one-file-system to stay on the root filesystem. In modern GNU tar, -l means --check-links, not "one filesystem".
  • umask 077 matters. The archive holds password hashes, SSH host keys and database credential files, so it must not be readable by everyone on the NAS share.
  • zstd (tar -I zstd) is much faster than bzip2 if it is available.

Schedule

0 0 * * 0 root /usr/local/bin/backup_system.sh >/dev/null 2>&1

Restore

Boot a rescue system, mount the new root at /mnt/sysimage, then run tar -xpjf <archive> -C /mnt/sysimage. Reinstall the boot loader, and fix /etc/fstab UUIDs if the disks changed.

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