On one of my customer’s devices, the backup software requires that the backups go to a separate partition (or drive). However, the customer only has one raid array and the bulk of the space is in /home. To work around this limitation, I created a raw image file called backup.img, which gets mounted as /backup. After the software performs its local backup, I use duplicity to backup /backup remotely to a backup server at my location (with encryption).
Today I got an alert that /backup was running low on space. It was an 80GB image and 61GB was in use, leaving only 15GB free. Now, this amount of free space should last quite a while. However, the software (cPanel) has a known issue for years that the 80% limit is hardcoded into the program. I can change this, but every time cPanel updates, it overwrites that change.
So to be proactive, I decided to go ahead and increase the image size.
In order to increase the size of an image, you simply unmount your raw image and use the dd command.
/sbin/e2fsck -f backup.img
e2fsck -f backup.img