backups using rsync

Polytropon freebsd at
Mon Mar 4 11:56:30 UTC 2013

On Mon, 04 Mar 2013 03:35:30 -0800, Ronald F. Guilmette wrote:
> Now, unfortunately, I have just been bitten by the evil... and apparently
> widely known (except to me)... ``You can't use dump(8) to dump a journaled
> filesystem with soft updates'' bug-a-boo.

There are other tools you can use, for example tar or cpdup
or rsync, as you've mentioned in the subject.

> I _had_ planned on using dump/restore and making backups from live mounted
> filesystems while the system was running.  But I really don't want to have
> to take the system down to single-user mode every week for a few hours while
> I'm making my disk-to-disk backup.  So now I'm looking at doing the backups
> using rsync.

The same problems that apply when dumping live systems can
bite you using rsync, but support for this "on file system
level" seems to be better in rsync than what dump does "on
block level".

> If I use all of the following rsync options...  -a,-H,-A, -X, and -S ....
> when trying to make my backups, and if I do whatever additional fiddling
> is necessary to insure that I separately copy over the MBR and boot loader
> also to my backup drive, then is there any reason that, in the event of
> a sudden meteor shower that takes out my primary disk drive while leaving
> my backup drive intact, I can't just unplug my old primary drive, plug in
> my (rsync-created) backup drive, reboot and be back in the sadddle again,
> almost immediately, and with -zero- problems?

You would have to make sure _many_ things are consistent
on the backup disk.

Regarding terminology, that would make the disk a failover
disk, even if the act of making it the actual "work disk"
is something you do manually.

The disk would need to have an initialized file system and
a working boot mechanism, both things rsync does not deal
with, if I remember correctly. But as soon as you have
initialized the disk for the first time and made sure (by
testing your first result of a rsync run), it should work
with any subsequent change of data you transfer to that

> P.P.S.  Before anyone asks, no I really _do not_ want to just use RAID
> as my one and only backup strategy. 

RAID _is_ **NO** backup. It's for dedundancy and performance.
If something is erased or corrupted, it's on all disks. And
all the disks permanently run. A backup disk only runs twice:
when backing something up, or when restoring. In your case,
restoring means that the disk is put into operation in its
role as a failover disk.

> RAID is swell if your only problem
> is hardware failures. 

Still hardware failures can corrupt data on all participating

> As far as I know however it will not save your
> bacon in the event of a fumble fingers "rm -rf *" moment.  Only frequent
> and routine actual backups can do that.

Correct. It's important to learn that lesson _before_ it is
actually needed. :-)

Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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