AIX

I just upgraded my AIX6.1 NIM server to AIX7 with a DVD I received from my vendor. I noticed that I got an AIX7 TL0 SP1 DVD, which is quite old, so I hoped not to have too much trouble upgrading. Alas.

As the upgrade nearly finished, it asked to load DVD #2, but when I did that, it barfed an error message about some drivers not being able to load. As I had booted from the first DVD, I suspected an error on DVD2 (maybe it was corrupt ?) and switched back to DVD1. Once that was loaded, I was greeted with the following error message :

0301-154 bosboot: missing proto file: /usr/lib/drivers/pci/sissas64_dd

The installation stopped, and I had no other choice than rebooting. But as the bosboot command had failed, no bootable disks were found. Panic ! The only choice I had, it seemed, was to revert to the AIX6 mksysb I luckily had prepared before the upgrade, but I decided to boot the lpar from the AIX7 DVD in maintenance mode and see what I could rescue. After all, only the bootblock was missing.

The missing driver in /usr/lib/drivers/pci/sissas64_dd was indeed missing from the DVD, and it seems that this is a bug in the AIX7 TL0. Fix was provided in TL0SP3.

I decided to try some last command, by copying the /usr/lib/drivers/pci/sissas_dd to sissas64_dd, after which the bosboot command wonderfully worked ! After rebooting the LPAR again, it booted nicely from the bootdisk and I was greeted with the AIX7 login prompt. Pffew !

We all know that you can modify online certain attributes on AIX devices, like queue_depth on disks for example :

# chdev -l hdisk15 -a queue_depth=16

However, some attributes changes need a reboot as the device property is in use at that time. You can modify the property by specifying that it will be modified at boot time, with the 'chdev -P' option. This can lead to quite some confusion : imagine a junior sysadmin changing the property, but forgetting the reboot. The 'lsattr' command will report the modified value, but not if it is effectively in use.

We can obtain the currently used value by interrogating the AIX kernel with the kernel debugger, quite a handy feature.
The following command shows the current value of cmd_num_elems on the virtual fiber adapter :

echo vfcs fcs0 | kdb | grep num_cmd_elems 

The following command lists the current values of the queue_depth parameter on hdisk15 :

# echo scsidisk hdisk3 |kdb |grep queue
    ushort queue_depth   = 0x8;

Over the years, I've fallen in love with the AIX multibos command. Here's a little procedure howto test patches without even a reboot of the system :

• First, clear out all references to old multibos instances :

# multibos -R

# mount nim:/patches /mnt

# multibos -Xs
[...]
# multibos -Xac -l /mnt/6100-07-07

# multibos -S
	MULTIBOS> oslevel -s
	6100-07-07-1316

# bootlist -m normal -o
hdisk0 blv=bos_hd5 pathid=0
hdisk0 blv=bos_hd5 pathid=1
hdisk0 blv=hd5 pathid=0
hdisk0 blv=hd5 pathid=1