[Discuss] Dropping obsolete commands (Linux Pocket Guide) (dump/restore)

[bogstad at pobox.com (Bill Bogstad)]

On Tue, Nov 10, 2015 at 11:24 AM, Chuck Anderson <cra at wpi.edu> wrote:
> On Tue, Nov 10, 2015 at 12:06:03PM +0000, Edward Ned Harvey (blu) wrote:
>> If you want to backup the entire filesystem in such a way that all the above is unnecessary - you instead boot from rescue media, partition & format the hard disk, and simply run "restore" and boot back into the restored system as if no problem had ever occurred, then assuming you're using ext filesystems, you need dump & restore. (Or you need storage on some snapshotting storage system external to the system you're restoring.)
>
> According to Ted Ts'o (filesystem developer), it is NOT a recommended
> way to backup your filesystem:
>
> http://www.gossamer-threads.com/lists/linux/kernel/1197768
>
> "It does read the mounted block device directly, and so it's certainly
> not a _recommended_ way to back up your ext4 filesystem. It should
> work, though, since it just uses the high-level libext2fs functions
> --- and a while back, I think I did a quick test and found that it
> really did work. So I'm not sure what broke, but it might not be that
> hard to fix. That being said, it may not be worth it to fix it, since
> with delayed allocation, backups using dump will be even more
> unreliable than they were before. " - Ted Ts'o

Note that this is from 2010 AND it was for a live (mounted
filesystem).  I've used the rsync method myself to copy a system disk,
but I've always been worried that if I didn't get the options just
right I might lose an ACL or some other extended attribute and not
know it.    "Runs fine" doesn't mean some subtle problem (possibly
security related?) hasn't been created.  For stuff in /home, I worry
much less about this and see no reason not to use rsync.

I'm about to add an SSD to a system with an HD and I'm going to give
"dump | restore" a try.
One interesting feature of the Linux dump is that you can specify
inodes not to backup and if it is a directory the whole subtree will
not be copied.   The system in question has /, /var, and /home all on
one partition and I'm going to split them up in the new configuration
so this will be helpful.   /home is going to stay on the HD while / is
moving to the SSD.  Not sure about /var yet.

Bill Bogstad