Multibos

 

Is it possible to have 2 BOS instance in a single rootvg and do patching on only 1 instance.

Yes. It is possible with the introduction of multibos.

“multibos” command allows the administrator to create multiple instances of AIX on the same rootvg. multibos setup operation actually creates a standby BOS that boots from a distinct logical volume. This creates 2 bootable sets of BOS on a single rootvg. Administrator can boot from either instance of BOS by specifying the respective BLV as an argument to the bootlist command.

The multibos command allows the administrator to access, install maintenance and technology levels for, update, and customize the standby BOS either during setup or in subsequent customization operations. Installing maintenance and technology updates to the standby BOS does not change system files on the active BOS. This allows for concurrent update of the standby BOS, while the active BOS remains in production.

In addition, the multibos command has the ability to copy or share logical volumes and file systems. By default, the BOS file systems (currently /, /usr, /var, and /opt,) and the boot logical volume are copied. You can also make copies of other file systems using –L flag.

ll other file systems and logical volumes are shared between instances of BOS. Separate log device logical volumes (for example, those that are not contained within the file system) are not supported for copy and will be shared.

But there are some restrictions for implementing multibos.

• The multibos command is supported on AIX 5L Version 5.3 with the 5300-03 Recommended Maintenance package and later.
• The current rootvg must have enough space for each BOS object copy. BOS object copies are placed on the same disk or disks as the original.
• The total number of copied logical volumes cannot exceed 128. The total number of copied logical volumes and shared logical volumes are subject to volume group limits.

 

Lets see some examples,

1. To preview the creation of a standby BOS,

# multibos –sXp

My recommendation: Always preview (-p flag) the setup operation becore proceeding with the actual operation

2. To create a standby BOS,

# multibos –sX

3. To mount a standby BOS,

# multibos –m

4. To unmount a standby BOS,

# multibos –u

5. To remove a standby BOS,

# multibos –R

6. To start a standby BOS shell,

# multibos –S

After starting a standby BOS shell, you can do patching or customize the BOS.

7. To setup bootlist for the standby BOS,

# bootlist pm normal hdisk0 blv=bos_hd5

whereas bos_hd5 is the BLV for the standby BOS which was created by multibos setup operation.

If you want to boot from the old BOS, please boot from hd5.

I started using multibos to avoid alt_disk_install during patching. This saves a lot of downtime for me. After the creation of standby BOS, we do patching in the standby bos which happens during production time with no downtime. We need downtime only to boot the machine in standby BLV. Its very simple. Have a try.

Man Page for multibos