[Libguestfs] [PATCH v3 1/2] NEW API: add a new api wipefs
Wanlong Gao
wanlong.gao at gmail.com
Thu Feb 9 15:34:43 UTC 2012
On 02/09/2012 10:12 PM, Richard W.M. Jones wrote:
> On Wed, Feb 08, 2012 at 01:32:47PM +0800, Wanlong Gao wrote:
>> Add the new api wipefs to erase the filesystem signatures
>> on a device but now erase any data.
>
> Having had a bit of time to think about this, I think this comment is
> right:
>
>> -guestfs_zero should use wipefs. See wipefs(8).
>
> wipefs is generally better (than "zero") in that it knows about what's
> on the disk (via blkid) and only overwrites the minimum necessary to
> remove partition tables, RAID signatures etc. This is good.
>
> What's bad is that: (1) It probably doesn't work for formats that
> blkid doesn't understand. (2) It doesn't preserve sparseness,
> although arguably that doesn't matter because it's only overwriting
> stuff that should be non-zero already.
>
> Cf: libblkid/src/probe.c:blkid_do_wipe
> daemon/zero.c:do_zero
>
> On balance, I think that changing guestfs_zero to use wipefs is a
> better way to approach this, but I'm open to opinions on this ...
Yeah, I also considered about this, since wipefs can't erase the partition
table, but guestfs_zero does, so, I'm afraid that if I use wipefs(8) to
change the internal of guestfs_zero, the function also changed.
Then, I also considered about just using libblkid's api to implement this api,
guestfs_wipefs or guestfs_zero, but I looked into util-linux and found
that the blkid_do_wipe() was introduced recently, not for long, and it may
not be in RHEL5, so, I just used the wipefs(8) to do this thing.
Here, if you like to change guestfs_zero's internal to use wipefs, I'd like
to do it, too. ;-P
Thanks
-Wanlong Gao
>
> Rich.
>
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