[dm-devel] DM_snapshot_cow filesystem (dmsetup create snapshot)
Douglas McClendon
dmc.lists at filteredperception.org
Mon Nov 28 01:08:31 UTC 2011
On 11/27/2011 04:31 PM, Frederick Grose wrote:
> On Sat, Oct 29, 2011 at 4:49 PM, Alasdair G Kergon <agk at redhat.com
> <mailto:agk at redhat.com>> wrote:
>
> markmc did some code that shows how to read the format a few years
> ago here:
> http://people.gnome.org/~markmc/code/merge-dm-snapshot.c
> <http://people.gnome.org/%7Emarkmc/code/merge-dm-snapshot.c>
>
> Otherwise look at dm-snap-persistent.c in the kernel tree.
>
> Alasdair
>
>
> Users can easily exhaust a LiveUSB snapshot overlay by writing
> too many changes to the OS filesystem, such as by performing
> a yum update.
>
> Would such an 'exhausted' overlay be amenable to some sort of
> data recovery or forensics?
>
> If so, how so; if not, why not?
Can you not mount the exhausted dm snapshot? If you mean data recovery
or forensics beyond that, please elaborate.
I know I've had issues 'read-only' mounting ext3(2?3?4?) filesystems
before (on actually read-only block devices). Maybe some flags that
I've forgotten get past that, but worst case you can always fake a
writable device with a 2nd overlay/snapshot going to a writable device,
i.e. if you wanted to let fsck repair things.
-dmc
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