zfs discuss - Aug 2012 - How do I import a zpool with a file as a member device?

While attempting to fix the last of my damaged zpools, there''s one that
consists of 4 drives + one 60G file.  The file happened by accident - I
attempted to add a partition off an SSD drive but missed the cache
keyword.  Of course, once this is done, there''s no way to remove the
new
unwanted member.  I fixed this by creating a file with mkfile, and
adding the file as a mirror of the SSD partition, then removed the SSD
partition from the zpool and kept the file around.

Over time something went wrong with this zpool and it hung the OS from
booting, so I removed it from the machine, but held on to it so I could
attempt to recover.

I''m trying to recover it now, but when I try to import it without cache
and read only, it tells me a member is missing (the file of course). 
But, how do I pass the file name as a member of the zpool to the import
command?

Since it''s only 60g, I suppose I could dd the file over to an external
USB drive.  Would that work?  Do I have to write it to slice 0, or a
whole volume (slice 2)? I''m guessing this might be the path of least
resistance...

Or is there some hidden option to zpool import where you can pass it
file/device names that I''m no aware of?  (Attempting to use zpool
online
poolname /path/to/file doesn''t work since the zpool isn''t
imported yet.
Catch 22 there.) :)

Otherwise, I do have a backup of the /etc/zfs/zpool.cache that contains
references to this zpool, but it seems that this is corrupted and
prevents all zpool operations.  I''ve tried to replace the zpool
members,
but it won''t let me.  I''ve even used a hex editor to replace
the device
names in the zpool.cache file with the new device names, but it''s still
locked.  So I can''t use the zpool cache file as a way to point to the
file member.  Is there some way to clear the "corrupted" flag in the
zpool.cache from allowing zpool commands to work?

I''m on oi151a5, but this zpool was created around oi134/135 or so.

On 08/13/2012 12:48 PM, Ray Arachelian wrote:
> While attempting to fix the last of my damaged zpools, there''s one
that
> consists of 4 drives + one 60G file.  The file happened by accident - I
> attempted to add a partition off an SSD drive but missed the cache
> keyword.  Of course, once this is done, there''s no way to remove
the new
> unwanted member.  I fixed this by creating a file with mkfile, and
> adding the file as a mirror of the SSD partition, then removed the SSD
> partition from the zpool and kept the file around.
> 
> Over time something went wrong with this zpool and it hung the OS from
> booting, so I removed it from the machine, but held on to it so I could
> attempt to recover.
> 
> I''m trying to recover it now, but when I try to import it without
cache
> and read only, it tells me a member is missing (the file of course). 
> But, how do I pass the file name as a member of the zpool to the import
> command?
> 
> Since it''s only 60g, I suppose I could dd the file over to an
external
> USB drive.  Would that work?  Do I have to write it to slice 0, or a
> whole volume (slice 2)? I''m guessing this might be the path of
least
> resistance...
> 
> Or is there some hidden option to zpool import where you can pass it
> file/device names that I''m no aware of?  (Attempting to use zpool
online
> poolname /path/to/file doesn''t work since the zpool isn''t
imported yet.
> Catch 22 there.) :)
> 
> Otherwise, I do have a backup of the /etc/zfs/zpool.cache that contains
> references to this zpool, but it seems that this is corrupted and
> prevents all zpool operations.  I''ve tried to replace the zpool
members,
> but it won''t let me.  I''ve even used a hex editor to
replace the device
> names in the zpool.cache file with the new device names, but it''s
still
> locked.  So I can''t use the zpool cache file as a way to point to
the
> file member.  Is there some way to clear the "corrupted" flag in
the
> zpool.cache from allowing zpool commands to work?
> 
> I''m on oi151a5, but this zpool was created around oi134/135 or so.
See the -d option to zpool import.

--
Saso

On 08/13/2012 06:50 AM, Sa?o Kiselkov wrote:
> See the -d option to zpool import. -- Saso 
Many thanks for this, it worked very nicely, though the first time I ran
it, it failed.  So what -d does is to substitute /dev.  In order for it
to work, you also have to make links to the drive devices in the /dev tree.
 
I did this in the directory where the file-members live (not knowing
exactly off the top of my head which types of devices/slices zfs wanted)
and then I was able to mount the pool, since the physical devices were
c22t0d4-d7:

for i in d4 d5 d6 d7; do for dev in /dev/dsk/c22t0${i}*; do echo $dev;
ln -s $dev; done; done

After this, using the -d option worked beautifully.

Thanks for helping me recover my data. :)

On 08/13/2012 02:01 PM, Ray Arachelian wrote:
> On 08/13/2012 06:50 AM, Sa?o Kiselkov wrote:
>> See the -d option to zpool import. -- Saso
> 
> Many thanks for this, it worked very nicely, though the first time
> I ran it, it failed.  So what -d does is to substitute /dev.  In
> order for it to work, you also have to make links to the drive
> devices in the /dev tree.
> 
> I did this in the directory where the file-members live (not
> knowing exactly off the top of my head which types of
> devices/slices zfs wanted) and then I was able to mount the pool,
> since the physical devices were c22t0d4-d7:
> 
> for i in d4 d5 d6 d7; do for dev in /dev/dsk/c22t0${i}*; do echo
> $dev; ln -s $dev; done; done
> 
> After this, using the -d option worked beautifully.
> 
> Thanks for helping me recover my data. :)
> 
No problem. Btw, the substitution for /dev/dsk is documented in the
manpage. But glad it worked. Enjoy ;-)

Cheers,
--
Saso