linux-kernel - Re: btrfs userspace question - where's the utility to dump/restore?

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Date:	Sat, 19 Jan 2013 13:02:30 -0500
From:	Valdis.Kletnieks@...edu
To:	Hugo Mills <hugo-lkml@...fax.org.uk>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: btrfs userspace question - where's the utility to dump/restore?

On Thu, 17 Jan 2013 22:18:19 +0000, Hugo Mills said:

> On Thu, Jan 17, 2013 at 03:05:35PM -0500, Valdis Kletnieks wrote:
> > So I'm looking at playing with btrfs, and I start looking at the
> > userspace pieces I'll need.  What I can't find is an equivalent
> > of the ext[34] "dump/restore" package to dump data to an external
> > backup device. Is 'tar cf --acls --selinux --xattrs /external/fs.dump'
> > as good as it gets, or is something else recommended?
>
>    tar doesn't handle reflinks(+), so the above won't quite give you a
> complete duplicate. In the btrfs tool, there's send/receive, which
> should(*) be sufficient to deal with reflinks.

So I decided to try it out on the filesystem that I stash all my music
(mostly because I can survive without that filesystem if I trash it, and
I have a known good backup).

Apparently, send/receive isn't in the manpage, which is why I didn't
see it.  Fortunately, there's --help

[~] btrfs send --help
usage: btrfs send <command> <args>

    btrfs send [-v] [-i <subvol>] [-p <parent>] <subvol>
        Send the subvolume to stdout.

[~] btrfs send -v /mp3 > /disk2/backups/mp3.btrfs
ERROR: /mp3 is not read-only.
[~] mount -o remount,ro /mp3
[~] btrfs send -v /mp3 >| /disk2/backups/mp3.btrfs
ERROR: /mp3 is not read-only.

Bah. Obviously this isn't anywhere near as easy as it is for ext4.

/me wanders off to find more caffeine...

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