Re: [BackupPC-users] How to manage disk space?

[Holger P. <wb...@pa...>]

Hi,

Kris Lou wrote on 2015-04-15 12:57:54 -0700 [Re: [BackupPC-users] How to manage disk space?]:
> On Wed, Apr 15, 2015 at 12:00 PM, Dave Sill <de5...@sw...>
> wrote:
> 
> > A corollary would be: how do I know that the space BackupPC is using
> > doesn't include a bunch of cruft like files from systems that have been
> > removed from BackupPC, or file systems that have been removed, ...
> 
> Somebody might have a script to check this,

I doubt that, because it seems to be impossible to exactly define what the
script should look for :-).

If you change a backup definition to no longer include part of the files it
used to include, existing backups will still include those files, and that is
how it should be. In some cases you may wish to remove those files from
previous backups (because they were erraneously included), in others, you may
simply not need to back them up in the future (e.g. they were previously
created by hand, and now they're generated from data included in the backup).
There is no automatic way to decide this. You can always delete files you do
not need, but you could not undo the effect of files you would have needed
being automatically purged from the backup. Just imagine *accidentally*
removing files from your backup definition. If that would immediately mangle
your backup history, you would undoubtedly immediately switch to another
backup tool :-).

Yes, it would be possible (but complicated) to check if existing backups match
the current backup definition and alert you to differences, but it seems like
a *lot* of work without much gain. If you find out that your backups include
something they shouldn't, you should really change the backup definition *and*
remove the extraneous files (or decide that they won't do any harm until the
backups expire). While BackupPC does not natively support changing existing
backups, I believe there are user contributed scripts to do such things,
probably written by Jeffrey ;-).

As for hosts that have been removed, that is really easy to check:
ls -l $topdir/pc

If there are directories not corresponding to existing hosts, you can 'simply'
remove them - if you don't want to wait, move them to $topdir/trash and
BackupPC will take care of it for you. You won't immediately get back much
space, because all files are linked to the pool. BackupPC_nightly will proceed
to delete the pool files not referenced by other backups (which might take
several nights, depending on your configuration).

Aside from that, you probably need to trust BackupPC to work as designed :-).

Regards,
Holger