Dump questions

[Matthew Seaman]

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On 22/02/2010 14:30, Jerry McAllister wrote:
> No.   In multi-user, files are still changing.   The snapshot could
> possibly be made between parts of a change - between different writes
> to the file, so there could be some inconsistency.  In practice this 
> is not a big problem, but, single user with filesystems unmounted is 
> still the most absolute way of making sure a filesystem is quiescent 
> during a dump.   

Umm.... you don't *need* to go to single user to ensure a consistent
filesystem dump: unmounting the partition is sufficient, or remounting
it read-only.  It's just that shutting the system down and rebooting to
single user mode can save you a deal of faffing about trying to kill
off any processes still using the filesystem, which would otherwise
block your ability to unmount it.

Note too, it's *reboot* into single user ('shutdown -r now', then press
4 at the boot menu) not *drop* into single user ('shutdown now') which
doesn't unmount filesystems for you, although it should kill almost all
processes.

Single user has it's own disadvantages: generally there's no network
configured, and with the root partition mounted read-only, you can't
update /etc/dumpdates.

Whenever you boot into single user, remember to run 'fsck -p' to ensure
filesystem integrity.  I'm not sure what happens if you attempt to
dump'n'restore a dirty filesystem, but it's certainly going to have
unintended consequences if the filesystem is actually damaged rather
than just dirty.

	Cheers,

	Matthew

- -- 
Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
                                                  Kent, CT11 9PW
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