zfs discuss - Jul 2009 - How to check what''s on a given ZFS file system ?

Hi,
I''ve already sent a few posts around this issue, but haven''t
quite got the answer - so I''ll try to clarify my question :)

Since I have upgraded from 2008.11 to 2009.06 a new BE has been created. On ZFS,
that corresponds to two file systems, both (strangely) mounted on /. The old BE
corresponds to a file system of 7G, the new one to a fs of 3G. As I fall short
of space and do not need the old 2008.11 any more, I would like to work out how
to delete it. I know I should do beadm destroy <name>. But before I do
that I would like to understand what I am erasing in those 7G (makes sense,
doesn''t it ?).

In particular, I''d like to:
- understand what''s in that old 7G ?
- understand why the new environment only takes 3G
- possibly mount the old 7G to check what''s inside ? I''m
surprised it is said to be mounted on /
- understand what beadm destroy actually destroys !

Thanks very much !
Axelle

$ zfs list
NAME                       USED  AVAIL  REFER  MOUNTPOINT
rpool                     42.1G  5.90G  1.42G  /a/rpool
rpool/ROOT                10.5G  5.90G    18K  legacy
rpool/ROOT/opensolaris    7.18G  5.90G  6.75G  /
rpool/ROOT/opensolaris-1  3.30G  5.90G  7.39G  /
rpool/dump                 895M  5.90G   895M  -
rpool/export              28.4G  5.90G    19K  /export
rpool/export/home         28.4G  5.90G   654M  /export/home
rpool/export/home/axelle  27.8G  5.90G  27.4G  /export/home/axelle
rpool/swap                 895M  6.69G  88.3M  -

$ beadm list 
BE            Active Mountpoint Space Policy Created          
--            ------ ---------- ----- ------ -------          
opensolaris   -      -          7.57G static 2009-01-03 13:18 
opensolaris-1 NR     /          3.42G static 2009-07-20 22:38
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This message posted from opensolaris.org

On Mon, Jul 27, 2009 at 2:51 PM, Axelle
Apvrille<no-reply at opensolaris.org> wrote:
> Hi,
> I''ve already sent a few posts around this issue, but
haven''t quite got the answer - so I''ll try to clarify my
question :)
>
> Since I have upgraded from 2008.11 to 2009.06 a new BE has been created. On
ZFS, that corresponds to two file systems, both (strangely) mounted on /. The
old BE corresponds to a file system of 7G, the new one to a fs of 3G.
Not quite. "beadm list" and the "USED" column of "zfs
list" does not
always correspond to the sum of data size of all it''s
files/directories. Do something like this:
- mkdir /a (if not''s there already)
- beadm mount rpool/ROOT/opensolaris /a
- df -h /
- df -h /a
- beadm umount rpool/ROOT/opensolaris

Compare the output of df to the output of "beadm list", and
you''ll see
what I mean. Note that the df output should be similar to that of
"REFER" from "zfs list".
> As I fall short of space and do not need the old 2008.11 any more, I would
like to work out how to delete it. I know I should do beadm destroy
<name>. But before I do that I would like to understand what I am erasing
in those 7G (makes sense, doesn''t it ?).
>
> In particular, I''d like to:
> - understand what''s in that old 7G ?
> - understand why the new environment only takes 3G
some of the space is probably shared (as in they refer to the same
block) between the old and new environment (/var comes to mind). If
you destroy the old BE (which is essentially a "zfs destroy"), it
might be possible that you won''t be able to reclaim all that 7G space
if the new environment still refers to them.

It''s actualy odd that your old BE uses more space. In my setup the new
BE always uses most space. Try runnning this:

zfs get all | grep origin

> - possibly mount the old 7G to check what''s inside ?
use "beadm mount"
> I''m surprised it is said to be mounted on /
No they aren''t. The "mountpoint" property merely records what
the
mountpoint is or will be when the fs is mounted, and not the actual
current mountpoint. In your case rpool/ROOT/opensolaris is not mounted
anywhere. Do this

zfs get mounted,mountpoint,canmount rpool/ROOT/opensolaris
rpool/ROOT/opensolaris-1
> - understand what beadm destroy actually destroys !
This fs
> rpool/ROOT/opensolaris ? ?7.18G ?5.90G ?6.75G ?/
which should be a zfs clone of this fs, or the other way around
> rpool/ROOT/opensolaris-1 ?3.30G ?5.90G ?7.39G ?/
-- 
Fajar

Thanks - that answers my question ! :))
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