Ready for AIX recovery with mksysb and mkdvd

Ready for AIX recovery with mksysb and mkdvd

AnthonyEnglish | Feb 14 2011 | Comments (2) | Visits (11691) 

 

mksysb - an oldie but a goodie

Long before the days of HMCs, VIO servers and LPARs, AIX version 3 and 4 ran on standalone systems. A system had its own tape drive. This would be useful for mksysb backups, which backed up the rootvg. 

Reliability, Availability, Scalability 1990s style

Actually, a rootvg backup was usually a full backup of everything - including all the data - since the idea of separate disks and volume group for data was a luxury most of us hadn't thought of. I saw many sites which survived for 10 years on a single 1 GB SCSI disk. The backup tapes were kept in a cardboard box on top of the server and never taken off site. The server itself was next to the sysadmin's desk in the main office. Aircon was a business hours concept except when the server was out on the factory floor. In those cases the server's main protection from the less than pristine environment were several layers of dust.

Done and dusted

Gone are the days of dusty servers and decade-old disks, but some things have survived the test of time. Like the mksysb. The mksysb command has been around forever, but it's still a valuable tool. With the development of virtualisation, it's got wider use than recovering your system when your only 1 GB disk dies.

You can use a mksysb backup to:

• clone your OS, for example from a Standard Operating Environment (SOE) LPAR: a gold image
  
• migrate to new hardware
• a disaster recovery test

mkdvd for ISO images

We have the ability today to create a mksysb backup into an ISO format image using the mkdvd command. You can then copy that ISO file to a VIO server and use it as as a file-backed device by means of the Virtual Media Library (also called the Virtual Media Repository).  This allows you to present the mksysb backup on a virtual optical device without having to use a NIM server or rely on physical media such as DVDs. For more details on how this all holds together, see Reliable Restores.

Just temporary

The mkdvd command creates its own temporary file systems: one each for 

• making a new mksysb (unless you use an existing mksysb specified by the -m flag)
• a DVD file system structure from which a single ISO file will be built; and
  
• a location for the final ISO image (or images if the backup doesn't fit into 4.7 GB).
  

By default, these file systems are prefixed with /mkcd because the mkcd command was originally used to burn mksysbs onto physical CDs. And they are created in rootvg unless you specify an alternate volume group using the mkdvd -V flag. The mkdvd command is one of many reasons why it's smart toleave some spare disk in rootvg.

If you don't want to use the default file systems when you run mkdvd, you can overwrite them using the flags shown in the table below. For example, you may want to use an NFS mount for all your temporary workspace.

	Description	User-specified option	Default
	Location of existing mksysb	-m filename	Create new mksysb
	Volume group for new file systems	-V dvdfsvolumegroup	rootvg
	Location of new mksysb	-M mksysbtarget	/mkcd/mksysbimage
	File system for DVD file system structure	-C cdfsdir	/mkcd/cd_fs
	Location of final DVD images	-I cdimagesdir	/mkcd/cd_images

You don't only have to use mkdvd for mksysbs. You can also use the mkdvd command to create an ISO file of an existing directory structure. It's a simple way of sharing software around to several LPARs without copying it to them all. To create an ISO file of some directory and all that sails in her, use

mkdvd -r /some_directory -S

I use mkdvd all the time, because I use the Virtual Media Library all the time. It's really worth getting used to some of its most common flags.

For more information on mksysb and mkdvd, have a look at the article in the IBM Systems Magazine Reliable Restores.


Tags:  iso media mkdvd restore mksysb nim dvd backup virtual aix library vmlibrary virtual_optical_device rootvg repository