Re: btrfs-image and btrfs send related queries

[Roman Mamedov <rm@romanrm.net>]

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On Mon, 18 Apr 2016 16:13:28 +0200
Henk Slager <eye1tm@gmail.com> wrote:

> (your email keeps ending up in gmail spam folder)
> 
> On Mon, Apr 18, 2016 at 9:24 AM, sri <toyours_sridhar@yahoo.co.in> wrote:
> > I tried btrfs-image and created image file and ran btrfs-image -r to a
> > different disk. Once recovered and mounted, I can able to see data is
> > not zeroed out as mentioned in btrfs-image man page.
> 
> "different disk"  you mention, that is important info. If you doe the
> restore to a image file, that image file is sparse and all data blocks
> are read as zeros.
> 
> However, if you restore to a block device, then you can assume it just
> writes the device blocks for metadata and leaves the rest untouched.
> So trim whole device first or brute-force overwrite completely with
> zeros.
> 
> So maybe the man pages needs some correction / extra notes.
> 
> > I tried on same machine.

Does btrfs-image store/restore the FS UUID? If it does, then potentially both
the source FS and the restored one were visible at the same time to the kernel
with identical UUIDs, and maybe it was actually accessing/mounting the source
one.

-- 
With respect,
Roman

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