Boot Environments
Boot Environments Intro
Boot Environments feature helps you to have several separate environments with different Solaris versions (e.g. 11.2.7, 11.3.12. etc.), different package versions, different system configurations. Typically they are used to update Solaris systems (most of the work is done by IPS behind the scenes, but you can learn the mechanics of the process in the IPS Lab.
Boot environments use ZFS snapshot/clone technology so they can be created quickly and they don't consume storage space until you make changes. You can have as many Boot Environments as you want and keep different system configurations in them. By default, every time you update Solaris OS, a new boot environment is created (you can specify its name).
Protection from Human Errors
Task: You want to make updates to your system, but you want to be able to return back to the previous state.
Lab: We will use a Solaris 11 feature called Boot Environments. We'll create an extra boot environment as a backup (think saving your state in a shooting game). Then we'll make some fatal mistakes which make our system unbootable. After we failed to boot our default boot environment, we'll boot into the backup BE.
The only command you want to know to work with Boot Environments is
beadm(1M). Start with showing all boot environments in the system:
root@solaris:~# beadm list BE Active Mountpoint Space Policy Created -- ------ ---------- ----- ------ ------- solaris NR / 6.87G static 2011-11-14 13:13
Create a new boot environment:
root@solaris:~# beadm create solaris-backup
Check the status again:
root@solaris:~# beadm list BE Active Mountpoint Space Policy Created -- ------ ---------- ----- ------ ------- solaris NR / 7.13G static 2011-11-14 13:13 solaris-backup - 126.14M static 2011-11-15 11:09
Now pretend you are making some changes in the system configuration, creating and removing directories, and... Somebody has distracted you and instead of removing a temporary directory, you have typed:
root@solaris:~# rm -rf /usr
What??? You just have destroyed the whole /usr directory! You have
killed your system! Try ls or ps or any normal command. What do
you see? Even if you try to reboot your system using init 6, the
result is the same: Command not found. Try to "Power Off" your virtual
machine and reboot it—you'll see it won't boot. Don't wait too long,
3–5 minutes is enough to be sure that it doesn't boot. Hint: While
waiting for the system to reboot, press the ESC key to see the error
messages.
No worries! We have a backup! And you don't have to go and find the
backup tape in your fireproof cabinet, go through all the hassles of
restoring the unbootable system... Just when your VirtualBox VM shows
you the GRUB menu, choose the solaris-backup item instead of the
Oracle Solaris 11.3 which is the default.
SPARC version
If you are using a SPARC system for this lab (for
example, in Oracle Solutions Center we use logical domains for that)
then you need console access to be able to choose a different Boot
Environment. In the case of LDoms, you have to login in the Control
Domain and stop your guest domain with ldm stop lab0 (or whatever
domain name you are using). Then make sure the domain will not
auto-boot: ldm set-var auto-boot\?=false lab0 and start the domain
again: ldm start lab0. Now you can access the domain's console via
telnet localhost 5000. You will see the familiar ok prompt. Then
use boot -L to list existing Boot Environments.
{0} ok boot -L Boot device: /virtual-devices@100/channel-devices@200/disk@0:a File and args: -L 1 solaris 2 solaris-backup Select environment to boot: [ 1 - 2 ]: 2 To boot the selected entry, invoke: boot [] -Z rpool/ROOT/solaris-backup Program terminated {0} ok boot -Z rpool/ROOT/solaris-backup
It boots again! What a relief!
What now? List your boot environments again:
root@solaris:~# beadm list BE Active Mountpoint Space Policy Created -- ------ ---------- ----- ------ ------- solaris R / 7.13G static 2011-11-14 13:13 solaris-backup N - 126.14M static 2011-11-15 11:09
What does it mean? It means that you are now running solaris-backup
boot environment, but at the next reboot the system will try to boot the
solaris boot environment, which is corrupted. Let's fix that. The plan
is: activate your current BE, delete the solaris BE (as it's corrupted
anyway), create a new solaris BE and activate it.
root@solaris:~# beadm activate solaris-backup root@solaris:~# beadm destroy solaris root@solaris:~# beadm create solaris root@solaris:~# beadm activate solaris
Check your work:
root@solaris:~# beadm list BE Active Mountpoint Space Policy Created -- ------ ---------- ----- ------ ------- solaris R - 6.05G static 2012-11-14 16:35 solaris-backup N / 275.5K static 2012-11-14 16:22
Now you've got everything back. You can safely reboot into solaris BE
or you can continue working in solaris-backup until next reboot.
Boot Environments have many applications: you can update your system, installing packages into inactive boot environment; create boot environment snapshots etc. We leave it for your homework.