AIX

This may be a dumb question and the more I think about it the worst it seems!!

I have inherited some standalone systems where they are using the mksysb command to create a disk file image; this image is then backed up to Networker.

My dumb question is how would we go about restoring this image should the server need to be replaced (i.e. internal disks as well)?

The estate doesn't have a NIM and the servers are old enough that we have no HMC or Virtualisation.

Any ideas would be gratefully received.

Cheers
Bryan
Bryan Hardwick

As a matter of fact, there are no dumb questions - just dumb answers.


In fact this is a very good question! Backups are a worthless waste of space if they can't be restored so it is prudent to make sure they indeed can be.

I suppose you are not very proficient with AIX so i will start with some basics:

An mksysb image is a (bootable) backup of the systems default volume group - rootvg, where all the relevant filesystems - "/", "/usr", "/var", etc... are located. Do a

Code:

lsvg -l rootvg

to find out what exactly is in your rootvg. All this is backed up in such an image. There is a command "savevg", which does similar backups for any (non-rootvg) volume group which you may want to read up about.

Still, there is more to an mksysb: it also contains boot code and all the means to restore it to an empty hardware. In principle you can boot from an mkysb image and have the complete system (minus application data in VGs other than the rootvg) restored completely, including network interfaces, users, groups, print queues and whatever you have configured on your system.

So, to answer your question: from a working mksysb image you are able to restore the complete system with every customisation. Alas, there is a catch: You can direct the image to every device or a file like you do, but if you do not take the mksysb either from NIM or to a tape as destination the boot code will not be included. You will need to boot from a generic boot device (system CD-ROM, etc.) and then use the mksysb image to restore the system.

You may want to try this out on spare hardware to understand the process, before you really need to restore a system in the wake of some catastrophe.

I hope this helps.

bakunin

mksysb output is only 'bootable' when written to a bootable device (e.g., a tape).

mkcd is a command that can be used to create ISO files (or write directly to a cd/dvd if one is available) that can later be burned to a cd/dvd.

When mksysb is written to a file (e.g., to a NIM server) the NIM server can create a special SPOT that can be used to boot from and then restore the complete mksysb image.

you can try to install a new AIX system, restore old mksysb with alt_disk_mksysb to another disk in the system and boot from it. But I'm not sure if you will be able to do it, if the new and old AIX versions are different. I did it only once, but both AIX versions were the same. And in my case the mksysb backup was made from NIM. As bakunin write, you might have mksysb image without boot code.

I suppose it goes back to "When you try to boot what will you see?" If you are using a partitioned server or a whole physical server it should not matter either way. If you can get the console opened and then power on/activate you would (if there are no usable boot devices) drop into the SMS menus. You can then probe to see what devices are visible. You can force this by pressing the appropriate key at the right time during the start-up. Do you know how to do that?

I suppose one question to ask is "Do you have a mirrored pair of disks for your root volume group?" which should give you some resilience. If you don't know, then the output from the following would be useful:-

Code:

lsvg -p rootvg
lsvg -l rootvg
lscfg -vl hdisk0
bootlist -om normal

As has been commented, you really need to force the mksysb off the server you may need to recover such that you can boot from it, so tape, DVD or NIM server (yes, I know you haven't got NIM) because then you can select that device from the SMS menus to boot from and (hopefully) it will all recover.


If you have other volume groups, then we can work on how to save the structure and/or contents. If you have Networker backing up data over the network , then you will probably just want the structure so you can recover that then restore your data.

The output from:-

Code:

lsvg
lsvg | grep -v rootvg | while read vg
do
  lsvg -p $vg
  lsvg -l $vg
done

.... will help us plan. The best place to store the structure information is somewhere in the root volume group so that it is recovered from a mksysb when you really need it.

if you can elaborate on what you have then I'm sure we can help. It would also be useful to know if the recovery would be to the same/similar server or if there are going to be differences, e.g. do you have LVM mirrored disks and the recovery server has hardware mirrors so you only have half the storage etc.

Don't worry if you don't have all the answers yet. We can work on them later.


Kind regards,
Robin