I'm a Linux newbie. From what I've read, you can back up an entire partition like this:dd if=/dev/sda1 of=/media/external/backupCan anyone tell me if I need to worry about files being changed while doing this? Could it be that some critical system file might get changed during the dd operation and then when you want to restore the backup, it won't work?I'm on Ubuntu 12.04.
Backing up partition using dd and changing files
backup
Unfortunately this may not be safe when filesystem you are backing up like this is mounted. Consider such situation:Your backup is half way done (i.e. first half of partition is already written to backup file.Now you (or some program) make a copy of a file that happens to be located on the other half of partition. Filesystem knows nothing about you backup process but it decides that there is some space left at the beginning of partition and this is where your copy of file is made. Obviosly, your backup won't contain this file.Now since you think you have a copy of this file, you decide you don't need original file and deletes it. And right after that, your backup process comes to the place where this file was and write information to the backup file that this file was deleted.As you might expect, you end up without any copy of this file in your backup.  That's just an example and it isn't worst thing that could happen. 