background:
Being somewhat of a coward I have up to now dd whole filesystems for backup. Major drawback has become the excessive use of memory for those complete backups (which unfortunatelly also included free blocks)
question
I would like to backup now only the files inside the filesystem, but yet be able to recreate the filesystem if need be. While the data can be easily extracted (i.e. via rsync -a),
I wonder, if there are some cases I overlook where for instance the inode number assigned to the file would matter?
This is especcially with the background of backing up the / root filesystem with the system on it. I am not so much worried about the /home/ filesystem but would be imaginative enough to expect that some strange thing might be when restoring the / root filesystem and suddenly the inodes have changed?
A good answer would include a most comprising list of cases in which the inode number might matter and cause eventually trouble.
update
Some experimenting reveals that for instance the hard links (naturally referencing the same inode) might need some attantion. Unsure if they need to have to be reassigned necessarily the same inode.
Luckily the number of hardlinks on a plain ubuntu 12.04 here is only about 10 files (so that I can script-record them and repair if needed and rsync -a would not care about the inode number)
Example
one case I think important is the case of selinux security module as it bassically uses inode numbers. So this is already one case, but maybe there are others.
Update2
I just run a test backing up and restoring a dummy 12.04 Ubuntu system using rsync -aH while reformating the partition in between to setup a new ext4 by mkfs.ext4 /dev/sdX -U oldfsUUID. Essentially when the files where restored all the inodes used most often where not anymore related to the original ones. Luckily hence it seems that for this one case of my Ubuntu 12.04 setup the inodes did not seem to matter. I am aware that this does not prove much. I still would appreciate an answer with a list of problematic cases. The one selinux I already mentioned, but I think there might be more and hence the chance for a good answer from somebody who knows.