*2022 Update. As this was written some time ago and time flies, some minor changes to the script are needed. Our old friend udisks is now depreciated so instead it’s successor udisksctl has to be used. You can comment the line and add a new one /I corrected the script here this way/ or just replace it with the new one.*
Now before you read this article I strongly advise you to read those once first if you think you are not too familiar with this subject. The first one is located HERE and is a very good explanation on how to use rsync for full OS backup. The second one is a detailed explanation on backing up data on to external USB drive by Bobulous, which you can find HERE. The script in this article is a modified version of the original script created by Bobulous as I needed to achieve few other things as well.
It is kind of important to get your fstab file organized first. Do not forget to modify it so your external hard drive gets the same mount point every time it is mounted. For this you will have to find out what your drive UUID is. As an example, the line in my fstab file look like:
UUID=ff0ba5cf-dc79-4b96-a86b-a64f26154232 /mnt/sync ext4 user,noauto,noatime 0 0
As I wanted the drive to be used only for the purpose of system backup I did not want it working all the time, so I wanted not just to unmount, but eject it as well and switch it off after use. This is where udisks utility comes handy, if it is not installed on your system – you will have to install it so the script works as it should. But udisks does not use the UUID to handle the drive, so the correct device file mapping has to be found.
The first thing is to extract the UUID, this is done in variable declaration:
uuid=`cat /etc/fstab | grep ${mount_point} | cut -c 6-41`
Before using the script make sure the result of the commands is the UUID of your drive, take care of cut command and adjust it if the output is not exactly what you are expecting. Or instead of cut you can use sed command, which might be a bit more universal:
uuid=`cat /etc/fstab | grep ${mount_point} | sed -r ‘s_.*=(.*) ${mount_point}.*_\1_’`
though I haven’t tried it myself.
After the disk is successfully mounted the declaration of HDID takes care of finding the correct device file:
HDID=`ls -l /dev/disk/by-uuid/${uuid} | sed -r ‘ s_^.* -> ../../(…).$_\1_’`
If you are like me and find sed command often confusing – there is a great tutorial about it by Bruce Barnett.
The actual backup work is done by rsync command, but you may want to adjust it depending on your Linux distribution, I run it on Debian 7 and it works fine for me.
And this is the script itself, you can modify it to suit your needs:
#!/bin/bash
# Script to backup full ystem to the external USB drive.
# Specify the mount point here (DO NOT end mount_point with a forward-slash).
mount_point=’/mnt/sync’
# Set the backup path here (DO NOT end mount_point with a forward-slash).
backup_path=${mount_point}
#Find UUID by mount point
uuid=`cat /etc/fstab | grep ${mount_point} | cut -c 6-41`
echo “#####”
echo “”
# Check whether target volume is mounted, and mount it if not.
if ! mountpoint -q ${mount_point}/; then
echo “Mounting the external USB drive.”
echo “Mountpoint is ${mount_point}”
if ! mount ${mount_point}; then
echo “An error code was returned by mount command!”
exit 5
else echo “Mounted successfully.”
HDID=`ls -l /dev/disk/by-uuid/${uuid} | sed -r ‘ s_^.* -> ../../(…).$_\1_’`
echo “${HDID} is the backup drive ID”;
fi
else echo “${mount_point} is already mounted.”;
fi
# Target volume **must** be mounted by this point. If not, die screaming.
if ! mountpoint -q ${mount_point}/; then
echo “Mounting failed! Cannot run backup without backup volume!”
exit 1
fi
echo “Preparing to transfer differences using rsync.”
echo “Backup storage directory path is ${backup_path}”
echo “Starting backup of / . . . “
rsync -aAXHhv /* ${backup_path}/ –progress –delete –exclude={/dev/*,/proc/*,/sys/*,/tmp/*,/run/*,/mnt/*,/media/*,/lost+found}
# Ask user whether target volume should be unmounted.
echo -n “Do you want to unmount ${mount_point} and eject the drive (no)”
read -p “: ” unmount_answer
unmount_answer=${unmount_answer,,} # make lowercase
if [ “$unmount_answer” == “y” ] || [ “$unmount_answer” == “yes” ]; then
if ! umount ${mount_point}; then
echo “An error code was returned by command!”
exit 5
else echo “Dismounted successfully.”
# udisks –detach /dev/${HDID}
udisksctl power-off -b /dev/${HDID}
echo “Disk ejected.”;
fi
else echo “Volume remains mounted.”;
fi
echo “”
echo “####”
Vessinity's IT Blog - Vess Georgiev 