Boot Environments for Solaris 10 Branded Zones

Until recently, Solaris 10 Branded Zones on Solaris 11 suffered one notable regression: Live Upgrade did not work. The individual packaging and patching tools work correctly, but the ability to upgrade Solaris while the production workload continued running did not exist. A recent Solaris 11 SRU (Solaris 11.1 SRU 6.4) restored most of that functionality, although with a slightly different concept, different commands, and without all of the feature details. This new method gives you the ability to create and manage multiple boot environments (BEs) for a Solaris 10 Branded Zone, and modify the active or any inactive BE, and to do so while the production workload continues to run.

Background

In case you are new to Solaris: Solaris includes a set of features that enables you to create a bootable Solaris image, called a Boot Environment (BE). This newly created image can be modified while the original BE is still running your workload(s). There are many benefits, including improved uptime and the ability to reboot into (or downgrade to) an older BE if a newer one has a problem.

In Solaris 10 this set of features was named Live Upgrade. Solaris 11 applies the same basic concepts to the new packaging system (IPS) but there isn't a specific name for the feature set. The features are simply part of IPS. Solaris 11 Boot Environments are not discussed in this blog entry.

Although a Solaris 10 system can have multiple BEs, until recently a Solaris 10 Branded Zone (BZ) in a Solaris 11 system did not have this ability. This limitation was addressed recently, and that enhancement is the subject of this blog entry.

This new implementation uses two concepts. The first is the use of a ZFS clone for each BE. This makes it very easy to create a BE, or many BEs. This is a distinct advantage over the Live Upgrade feature set in Solaris 10, which had a practical limitation of two BEs on a system, when using UFS. The second new concept is a very simple mechanism to indicate the BE that should be booted: a ZFS property. The new ZFS property is named com.oracle.zones.solaris10:activebe (isn't that creative? ).

It's important to note that the property is inherited from the original BE's file system to any BEs you create. In other words, all BEs in one zone have the same value for that property. When the (Solaris 11) global zone boots the Solaris 10 BZ, it boots the BE that has the name that is stored in the activebe property.

Here is a quick summary of the actions you can use to manage these BEs:

To create a BE:

• Create a ZFS clone of the zone's root dataset

To activate a BE:

• Set the ZFS property of the root dataset to indicate the BE

To add a package or patch to an inactive BE:

• Mount the inactive BE
• Add packages or patches to it
• Unmount the inactive BE

To list the available BEs:

• Use the "zfs list" command.

To destroy a BE:

• Use the "zfs destroy" command.

Preparation

Before you can use the new features, you will need a Solaris 10 BZ on a Solaris 11 system. You can use these three steps - on a real Solaris 11.1 server or in a VirtualBox guest running Solaris 11.1 - to create a Solaris 10 BZ. The Solaris 11.1 environment must be at SRU 6.4 or newer.

1. Create a flash archive on the Solaris 10 system

   s10# flarcreate -n s10-system /net/zones/archives/s10-system.flar

2. Configure the Solaris 10 BZ on the Solaris 11 system

   s11# zonecfg -z s10z
   Use 'create' to begin configuring a new zone.
   zonecfg:s10z> create -t SYSsolaris10
   zonecfg:s10z> set zonepath=/zones/s10z
   zonecfg:s10z> exit
   s11# zoneadm list -cv
     ID NAME             STATUS     PATH                           BRAND     IP    
      0 global           running    /                              solaris   shared
      - s10z             configured /zones/s10z                    solaris10 excl  

3. Install the zone from the flash archive

   s11# zoneadm -z s10z install -a /net/zones/archives/s10-system.flar -p

You can find more information about the migration of Solaris 10 environments to Solaris 10 Branded Zones in the documentation.

The rest of this blog entry demonstrates the commands you can use to accomplish the aforementioned actions related to BEs.

New features in action

Note that the demonstration of the commands occurs in the Solaris 10 BZ, as indicated by the shell prompt "s10z# ". Many of these commands can be performed in the global zone instead, if you prefer. If you perform them in the global zone, you must change the ZFS file system names.

Create

The only complicated action is the creation of a BE. In the Solaris 10 BZ, create a new "boot environment" - a ZFS clone. You can assign any name to the final portion of the clone's name, as long as it meets the requirements for a ZFS file system name.

s10z# zfs snapshot rpool/ROOT/zbe-0@snap
s10z# zfs clone -o mountpoint=/ -o canmount=noauto rpool/ROOT/zbe-0@snap rpool/ROOT/newBE
cannot mount 'rpool/ROOT/newBE' on '/': directory is not empty
filesystem successfully created, but not mounted

You can safely ignore that message: we already know that / is not empty! We have merely told ZFS that the default mountpoint for the clone is the root directory.

(Note that a Solaris 10 BZ that has a separate /var file system requires additional steps. See the MOS document mentioned at the bottom of this blog entry.)

List the available BEs and active BE

Because each BE is represented by a clone of the rpool/ROOT dataset, listing the BEs is as simple as listing the clones.

s10z# zfs list -r rpool/ROOT
NAME               USED  AVAIL  REFER  MOUNTPOINT
rpool/ROOT        3.55G  42.9G    31K  legacy
rpool/ROOT/zbe-0     1K  42.9G  3.55G  /
rpool/ROOT/newBE  3.55G  42.9G  3.55G  /

The output shows that two BEs exist. Their names are "zbe-0" and "newBE".

You can tell Solaris that one particular BE should be used when the zone next boots by using a ZFS property. Its name is com.oracle.zones.solaris10:activebe. The value of that property is the name of the clone that contains the BE that should be booted.

s10z# zfs get com.oracle.zones.solaris10:activebe rpool/ROOT
NAME        PROPERTY                             VALUE  SOURCE
rpool/ROOT  com.oracle.zones.solaris10:activebe  zbe-0  local

Change the active BE

When you want to change the BE that will be booted next time, you can just change the activebe property on the rpool/ROOT dataset.

s10z# zfs get com.oracle.zones.solaris10:activebe rpool/ROOT
NAME        PROPERTY                             VALUE  SOURCE
rpool/ROOT  com.oracle.zones.solaris10:activebe  zbe-0  local
s10z# zfs set com.oracle.zones.solaris10:activebe=newBE rpool/ROOT
s10z# zfs get com.oracle.zones.solaris10:activebe rpool/ROOT
NAME        PROPERTY                             VALUE  SOURCE
rpool/ROOT  com.oracle.zones.solaris10:activebe  newBE  local
s10z# shutdown -y -g0 -i6

After the zone has rebooted:

s10z# zfs get com.oracle.zones.solaris10:activebe rpool/ROOT
rpool/ROOT  com.oracle.zones.solaris10:activebe  newBE  local
s10z# zfs mount
rpool/ROOT/newBE                /
rpool/export                    /export
rpool/export/home               /export/home
rpool                           /rpool

Mount the original BE to see that it's still there.

s10z# zfs mount -o mountpoint=/mnt rpool/ROOT/zbe-0
s10z# ls /mnt
Desktop                         export                          platform
Documents                       export.backup.20130607T214951Z  proc
S10Flar                         home                            rpool
TT_DB                           kernel                          sbin
bin                             lib                             system
boot                            lost+found                      tmp
cdrom                           mnt                             usr
dev                             net                             var
etc                             opt

Patch an inactive BE

At this point, you can modify the original BE. If you would prefer to modify the new BE, you can restore the original value to the activebe property and reboot, and then mount the new BE to /mnt (or another empty directory) and modify it.

Let's mount the original BE so we can modify it. (The first command is only needed if you haven't already mounted that BE.)

s10z# zfs mount -o mountpoint=/mnt rpool/ROOT/zbe-0
s10z# patchadd -R /mnt -M /var/sadm/spool 104945-02

Note that the typical usage will be:

1. Create a BE
2. Mount the new (inactive) BE
3. Use the package and patch tools to update the new BE
4. Unmount the new BE
5. Reboot

Delete an inactive BE

ZFS clones are children of their parent file systems. In order to destroy the parent, you must first "promote" the child. This reverses the parent-child relationship. (For more information on this, see the documentation.)

The original rpool/ROOT file system is the parent of the clones that you create as BEs. In order to destroy an earlier BE that is that parent of other BEs, you must first promote one of the child BEs to be the ZFS parent. Only then can you destroy the original BE.

Fortunately, this is easier to do than to explain:

s10z# zfs promote rpool/ROOT/newBE 
s10z# zfs destroy rpool/ROOT/zbe-0
s10z# zfs list -r rpool/ROOT
NAME               USED  AVAIL  REFER  MOUNTPOINT
rpool/ROOT        3.56G   269G    31K  legacy
rpool/ROOT/newBE  3.56G   269G  3.55G  /

Documentation

This feature is so new, it is not yet described in the Solaris 11 documentation. However, MOS note 1558773.1 offers some details.

Conclusion

With this new feature, you can add and patch packages to boot environments of a Solaris 10 Branded Zone. This ability improves the manageability of these zones, and makes their use more practical. It also means that you can use the existing P2V tools with earlier Solaris 10 updates, and modify the environments after they become Solaris 10 Branded Zones.