Re: subvolume/snapshot usage question

[Goffredo Baroncelli <kreijack@alice.it>]

Hello tsuraan,

"bcp" is what you need. "bcp" is part of "btrfs-prog-unstable"

See http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg02292.html


BR
Goffredo

On Saturday 22 August 2009, tsuraan wrote:
> Suppose I have a directory under my home on a btrfs filesystem where I
> store virtual machine images.  I have one base virtual machine, and
> from it I make copies that I actually run.  To make a copy of a VM
> today, I do cp -r, which seems pretty wasteful since the VMs are
> almost entirely identical.  Is there some way that I can do a snapshot
> of just the directory that holds my base VM, and then mount different
> "forks" of that snapshot to be the bases of my different running
> machines?
> 
> It looks like I could create a snapshot of the root of my btrfs
> filesystem for each vm, mount that snapshot somewhere, and run the vm
> from that full fs snapshot, but that's not ideal.  I could also create
> a large file for my base VM directory, format it btrfs, mount it using
> the loopback device, and then mount snapshots of that loopback
> filesystem, but having to preallocate filesystem space for my VMs is
> not as nice as being able to share space with the rest of my
> filesystem.  Is there a partial-snapshot capability in btrfs?  I don't
> understand what subvolumes are, and I think they're unrelated to what
> I want, but the name sounds promising...
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