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Automated Raspberry Pi Backup – complete image

I love my Raspberry Pi projects and I run a lot of specialist "mini" servers at home doing everything from torrent sharing of Linux distros to media streaming and media playing. But all Raspberry Pi's and other single board computers that rely on SD-cards sooner or later comes to a point where they trash the card and doesn't boot again.

Every time I run into that situation without remembering exactly what was running and how on the particular Raspberry Pi. I want backups, not just the backup I usually do right after installation but a last night backup or similar. So I put up an NFS share on my NAS to store the backups, it will work just as well with a USB stick connected directly to the Raspberry Pi. Here is a step by step guide how I automated the backups on all my Raspberry Pi's. This script will create a complete image of the SD-card while the Raspberry Pi is running. You can just write that image to a new SD-card and pop it into the Pi and it will be like nothing happened!

  1. Create the folder /mnt/backup
  2. Edit fstab with
    sudo /etc/fstab

    Add the share on the NAS for mounting /mnt/backup nfs rsize=8192,wsize=8192,timo=14,intr 0 0
  3. Test the mount
    sudo mount -a
  4. Download my backup script from Github
    wget https://github.com/kallsbo/BASH-RaspberryPI-System-Backup/raw/master/system_backup.sh

    I placed the script on my NAS share so all the Raspberry Pi's could use the same script file.

  5. Make the script file executable
    chmod +x system_backup.sh
  6. Add it to crontab. Since the script needs to be executed as root we need to edit the root crontab.
    sudo crontab -e

    Just add the line (with correction for the path to the script)

    0 3 * * * /mnt/backup/system_backup.sh

The script is a simple bash script that you can look at and download from Github - BASH-RaspberryPI-System-Backup. The script has two variables, backup_path and rentention_days. The first is the path where to store the backup and the second is the number of days to save it. They can have defaults set in the script but you can override them by supplying command line arguments like:

sudo ./system_baskup.sh /mnt/otherpath 7

That will give you the backup path of /mnt/otherpath and a retention of 7 days. The next few lines (until line 38) just checks if it's running as root and checks for command line arguments. Then we touch the file /boot/forcefsck this creates a blank file at that path and forces the Raspberry Pi to check the filesystem on the next boot. This is so the backup image, if used, will be checked for filesystem inconsistencies on first boot.

Then comes the magic sauce, creating a complete copy of the SD-card:

dd if=/dev/mmcblk0 of=$backup_path/$HOSTNAME.$(date +%Y%m%d).img bs=1M

Then the script removes the /boot/forcefsck file so the force file is only in the backup image and not on the currently running SD-card. Then it looks for backups older then the number of retention days and deletes them. Since the script includes the hostname in the filename and only looks for it's own hostname you can have several Raspberry Pi's backing up to the same location without being worried about them deleting each others backups.

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