Zones, ZFS and snapshots (making your life easier)

Maybe like me you play around a lot with software installations. For example you would like to install and configure the latest Identity Manager. The problem is that it is very easy to screw up an environment. Is it possible to rollbak some modifications you made to the zone ? Easily ? The answer is : YES. Very easily.

--> existing zones on my system

root@catalogne:~# zoneadm list -iv
ID NAME STATUS PATH BRAND IP
0 global running / native shared
- identity_manager_80 installed /zones/identity_manager_80 ipkg shared
- sparse installed /z/sparse ipkg shared
- identity-manager-80 installed /z/identity-manager-80 ipkg shared

Let's play a little with the zone name identity-manager-80 !

--> booting the zone

root@catalogne:~# zoneadm -z identity-manager-80 boot

To create a snapshot of a zone we need to use zfs snapshot.

Some theory :

root@catalogne:~# zfs
missing command
usage: zfs command args ...
where 'command' is one of the following:
...
snapshot [-r] [-o property=value] ...
...

ZFS filesystems :

root@catalogne:~# zfs list
NAME USED AVAIL REFER MOUNTPOINT
rpool 14.8G 83.1G 74K /rpool
rpool/ROOT 4.10G 83.1G 18K legacy
rpool/ROOT/opensolaris 4.10G 83.1G 3.96G /
rpool/dump 1.62G 83.1G 1.62G -
rpool/export 3.75G 83.1G 19K /export
rpool/export/home 3.75G 83.1G 19K /export/home
rpool/export/home/rudy 3.75G 83.1G 3.75G /export/home/rudy
rpool/identity_manager_80 2.49G 83.1G 21K /zones/identity_manager_80
rpool/identity_manager_80/ROOT 2.49G 83.1G 18K legacy
rpool/identity_manager_80/ROOT/zbe 2.49G 83.1G 2.49G legacy
rpool/share 18K 83.1G 18K /zones/share
rpool/swap 1.62G 84.7G 53.3M -
rpool/z 1.22G 83.1G 1006M /z
rpool/z/identity-manager-80 5.09M 83.1G 21K /z/identity-manager-80
rpool/z/identity-manager-80/ROOT 5.07M 83.1G 18K legacy
rpool/z/identity-manager-80/ROOT/zbe 5.05M 83.1G 240M legacy
rpool/z/sparse 239M 83.1G 21K /z/sparse
rpool/z/sparse/ROOT 239M 83.1G 18K legacy
rpool/z/sparse/ROOT/zbe 239M 83.1G 238M legacy
rpool/zones 18K 83.1G 18K /rpool/zones

If we look closely to identity-manager-80 we retrieve 1 filesystem to snapshot :identity-manager-80.
Is identity-manager-80 the one to snapshot ? Answer : NO !
Let's proove that it is not /z/identity-manager-80.

--> let's open a console :

root@catalogne:~# zlogin -C identity-manager-80
[Connected to zone 'identity-manager-80' console]

identity-manager-80 console login: root
Password:
Mar 5 09:26:42 identity-manager-80 login: ROOT LOGIN /dev/console
Last login: Wed Mar 4 17:56:46 on console
Sun Microsystems Inc. SunOS 5.11 snv_101b November 2008

--> let's create a big file : big and size of big is 500 mb.

root@identity-manager-80:~# mkfile 500m bigfile

root@identity-manager-80:~# mkfile 500m bigfile_to_disappear
root@identity-manager-80:~# ls -lrt
total 936067
-rw------- 1 root root 524288000 Mar 5 09:28 bigfile

--> let's review the filesystems

root@catalogne:~# zfs list
NAME USED AVAIL REFER MOUNTPOINT
rpool 15.2G 82.7G 74K /rpool
rpool/ROOT 4.10G 82.7G 18K legacy
rpool/ROOT/opensolaris 4.10G 82.7G 3.96G /
rpool/dump 1.62G 82.7G 1.62G -
rpool/export 3.75G 82.7G 19K /export
rpool/export/home 3.75G 82.7G 19K /export/home
rpool/export/home/rudy 3.75G 82.7G 3.75G /export/home/rudy
rpool/identity_manager_80 2.49G 82.7G 21K /zones/identity_manager_80
rpool/identity_manager_80/ROOT 2.49G 82.7G 18K legacy
rpool/identity_manager_80/ROOT/zbe 2.49G 82.7G 2.49G legacy
rpool/share 18K 82.7G 18K /zones/share
rpool/swap 1.62G 84.3G 53.3M -
rpool/z 1.63G 82.7G 1006M /z
rpool/z/identity-manager-80 419M 82.7G 21K /z/identity-manager-80
rpool/z/identity-manager-80/ROOT 419M 82.7G 18K legacy
rpool/z/identity-manager-80/ROOT/zbe 419M 82.7G 654M legacy
rpool/z/sparse 239M 82.7G 21K /z/sparse
rpool/z/sparse/ROOT 239M 82.7G 18K legacy
rpool/z/sparse/ROOT/zbe 239M 82.7G 238M legacy
rpool/zones 18K 82.7G 18K /rpool/zones

As you can see it is NOT rpool/z/sparse that increased BUT rpool/z/identity-manager-80/ROOT/zbe !
From 240M to 654M(col REFER)

/ROOT/zbe has to be used and it is because ZFS filesystem data is not hierarchical. Only (most of) the configuration is.

--> Let's snapshot rpool/z/identity-manager-80/ROOT/zbe !

From the global zone

root@catalogne:~# zfs snapshot rpool/z/identity-manager-80/ROOT/zbe@snap0933

It means that a snapshot was taken from the dataset rpool/z/identity-manager-80/ROOT/zbe and the name is snap0933(taken at 9h33).

--> List of the snapshots

root@catalogne:~# zfs list -t snapshot
NAME USED AVAIL REFER MOUNTPOINT
rpool/ROOT/opensolaris@install 138M - 2.21G -
rpool/z/identity-manager-80/ROOT/zbe@snap0933 0 - 740M -
rpool/z/sparse/ROOT/zbe@identity-manager-80_snap 542K - 236M -

We can retrieve in the list that snapshot that interest us : rpool/z/identity-manager-80/ROOT/zbe@snap0933.

Let's go back to the zone and create a second bigfile. The idea is to rollback the zone using the znapshot we have just taken and see what happened !

root@identity-manager-80:~# mkfile 500m bigfile_to_disappear
root@identity-manager-80:~# ls -lrt
total 936067
-rw------- 1 root root 524288000 Mar 5 09:28 bigfile
-rw------- 1 root root 524288000 Mar 5 09:37 bigfile_to_disappear

--> Let's rollback the zone using the snapshot(from the global zone)

root@catalogne:~# zfs
missing command
usage: zfs command args ...
where 'command' is one of the following:
...
rollback [-rRf]
...

But it is always better to shutdown the zone(clean state).

root@catalogne:~# za -z identity-manager-80 halt

--> The zone was shutdown.

root@identity-manager-80:~#
[NOTICE: Zone halted]

--> The snapshot is rollbacked.

root@catalogne:~# zfs rollback rpool/z/identity-manager-80/ROOT/zbe@snap0933

--> The zone is booted again.

root@catalogne:~# za -z identity-manager-80 boot

[NOTICE: Zone booting up]


SunOS Release 5.11 Version snv_101b 64-bit
Copyright 1983-2008 Sun Microsystems, Inc. All rights reserved.
Use is subject to license terms.
Hostname: identity-manager-80
Reading ZFS config: done.
Mounting ZFS filesystems: (5/5)

--> Login as root again.

identity-manager-80 console login: root
Password:
Mar 5 09:42:11 identity-manager-80 login: ROOT LOGIN /dev/console
Last login: Thu Mar 5 09:26:42 on console
Sun Microsystems Inc. SunOS 5.11 snv_101b November 2008
root@identity-manager-80:~# ls
bigfile

Youpee ! Indeed the file bigfile_to_disappear is gone !

That's all for today. I hope it will make your life easier because you can try something and then make it gone !

All you need is ZFS !!!

-Rudy-