Re: [gentoo-user] backup to a cold-swap drive

[Florian Philipp]

Am 29.04.2010 02:38, schrieb Iain Buchanan:
> Hi & thanks,
>
> On Wed, 2010-04-28 at 17:31 +0200, Florian Philipp wrote:
[...]
>
>> If you can live with just one big partition as a backup (probably with
>> separate /boot), you should replace fstab and grub.conf on the backup
>> medium and blacklist them from the files which you want to back up.
>
> why wouldn't I backup fstab and grub.conf as well?  If my internal disk
> dies, I assume I'll swap them over, meaning grub and fstab will have to
> be the same.

I think you misunderstood me or I didn't explain it correctly. I try it
again:

You probably have a lot of partitions on your internal disk; one for /,
/usr and /home, for example. My reasoning was that it is probably easier
to have just one big partition on your backup medium instead of many
small ones. If you would then swap your backup medium in, with exactly
the same fstab as in your original installation, your system would try
to mount partitions which are simply not there. Therefore you need a
different fstab and most likely also another grub.conf.

>
>> Concerning the backup tool, I would use `rsync --delete` plus all
>> relevant switches for permissions, times, acls, etc. If you use another
>> tool, just make sure it doesn't put some metadata onto the backup medium
>> and that it can delete files which no longer exist on the original medium.
>
> I was thinking of rsync, but I didn't want to do it in an hourly cron
> fashion, I was hoping for some "gamin" alteration-triggered idea.
>

Ah, I see what you mean. I've never worked with the file alteration
monitor (FAM) but once evaluated inotify for some administrative
purposes. AFAIK they are not scalable good enough to work on a system
wide basis. For example, I think the default limit of observable files
with inotify is 8192.

>> With regard to your requirement to just 'pull the cord' without
>> umounting it:
>
> I wasn't thinking of pulling the chord without unmounting, I was
> thinking of the machine dying, hence leaving the disk in a non-shutdown
> state.
>

Okay, I thought you meant the unreliable power at those "weird
locations" you were talking about. Such a black-out or brown-out is
basically the same as pulling the cord.

> thanks for the tips :)  rsync will at least get me going quickly.
> Yesterday I tried iotop to with dd - some slowness but otherwise quite
> nice.
>

To reduce the performance impact, you can also use the ionice command.

Hope this helps,
Florian Philipp