Nice example for the power of boot environments

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Nice example for the power of boot environments

Tuesday, October 4. 2011

There is a nice example of the power of boot environment. Boot environments are something like snapshots of your operating system installation made writeable. As you may already assume, they are based on ZFS snapshots and the clone functionality. This is possible due to the usage of ZFS as the root filesystem.

So: Please don't try this at home. Whey you try it, don't try it on any Solaris 11 Express installation of any value. But don't try it. I don't want to hear any story. that you've deleted your ERP system by accident because you used the wrong terminal window. Leave that to trained professional stunt admins with the right equipment (Solaris 11 Express)

Assume you have a system, configured with all your application, everything is running fine. So you think it would be nice to have something like a freezed state of this situation. No problem. This command will do the trick.

# beadm create rescuenet
# init 6

When you reboot your system you will see it as a new entry in the grub menu.

Okay, but boot into the old environment starting "Oracle Solaris ..." first by selecting it in the grub menu (it should be already selected, or you used beadm activate already. Now i will drop the atomic bomb on your installation.

# rm --no-preserve-root -rf /

Essentially we've just nuked the installation. After a moment the system should just freeze. Reset the system and boot again via grub into the boot environment starting with "Oracle Solaris ...":

Okay ... on a normal system this would send you to the tapes. With Solaris 11: Reset the system. Boot into the boot environment "rescuenet" via selecting it in grub.

Tada! Just creating a boot environment with a single command after a config change may safe your butt later .... and btw ... this even works in zones ... they know the concepts of boot environment,too.

Posted by Joerg Moellenkamp in English, Solaris, Sun/Oracle at 20:06 | Comments (7) | Trackbacks (0)

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How much of the original environment is actually left? Years ago I did this, and once it deleted libc.so (which was fairly fast because it seemed to be deleting by inode number, and that library was a pretty low inode number) that is when the system "freezes". Boot off of a cd/dvd and surprisingly most of the data is still there and accessible.

#1 solariswiz on 2011-10-05 00:17 (Reply)

On a related note, I updated my OpenSolaris b134 image to OpenIndiana b148 while using the system to write some code during the installation. And I can boot back and forth. Pretty cool.

Unfortunately Oracle Solaris builds don't play as nicely. It appears b173 breaks with the past -- you can't upgrade from Express to Early Adopter, or if you can I haven't figured out how. In other news, http://pkg.opensolaris.org was recently killed without warning. I guess no single playground is good enough for all the children...

#2 Michael Ernest (Homepage) on 2011-10-05 00:18 (Reply)

You can not upgrade from Solaris 11 Express to b173, but the real Solaris 11 will allow this. And to upgrade from OpenSolaris to Solaris 11, too.

#2.1 Kebabbert on 2011-10-06 12:59 (Reply)

This is one of the features I miss from Solaris' ZFS on FreeBSD, there are 'side' projects like 'manageBE' that allow BE on FreeBSD, but its PITA to properly setup BE on FreeBSD currently, maybe after some GSoC project ... ;p

#3 vermaden on 2011-10-05 08:31 (Reply)

That is pretty impressive, copy on write file systems are the way to go for sure and zfs seems to be miles ahead of the pack.
I would guess that this means the luadmin (live upgrade) suite of commands will no longer be needed.

#4 Stuart on 2011-10-05 13:25 (Reply)

Minimal offtopic, aber: wo geht man denn derzeit hin wenn man ein aktuelles Solaris11 Express / OpenSolaris / whatever zum Experimentieren will? Auf opensolaris.org gibts ja nur noch die paar halbtoten abgeleiteten Projekte (schilix, belenix etc), und auf oracle.com verlinkt S11 Express auf eine Live-CD vom letzten Jahr. Sowas antikes wollte ich mir eigentlich nicht antun. Oder soll ich gleich aufs Release von S11 warten? Sollte ja jetzt bald soweit sein

#5 Woo (Homepage) on 2011-10-06 17:01 (Reply)

Ich habe es in mit einer Solaris 11 EA - Installation in einer Guest LDOM getestet. Der rm Befehl kam irgendwann zurück (nach vielen Fehlermeldungen weil er u.a. im /proc und /dev* nicht alles löschen konnte. Danach ging nichts mehr. Die LDOM konnte nicht mehr booten, da das Boot-Archiv fehlte - wohl auch vom rm gelöscht worden. Da hilft dann auch kein Boot-Enviroment. ;-((

#6 Christian M. on 2011-11-02 07:30 (Reply)

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