Instance numbers for disks and tapes are discovered in backplane order (lowest first), then by SCSI bus ID (highest first), then (if applicable) LUN number (lowest first). When you first get a new box, the instance numbers start at the lowest numbered I/O card, typically just the multi-function card. We call this the Kitchen Sink Card because it has almost eveything except the kitchen sink on it.
However, the KSC is also the highest number in the backplane, but it is still the only card so instance numbers start at 0 for each driver. So far so good--but computers change and sysadmins add more stuff (to lower-numbered bus slots) and these new items will be scanned and added when the system reboots. Instance 0 is taken already so the new card(s) will start at instance 1. Still so far so good.
But let's cold install...if all those new cards and devices are left connected, then insf will see the lowest cards first and the KSC last. Now the KSC instance numbers are no longer 0. The system works fine but as mentioned, backup scripts or other files taken from the old environment will not match. LAN cards are similar. The lan0 device is the KSC when first installed but add a few additional LAN cards and cold install--the built-in LAN on the KSC is now lan3 or lan7...
So to control the creation order, you must disconnect devices that have been added since the original installation (that would cause a reordering of instance numbers). Then add the new cards in the order desired and reboot each time.
There is also a technique that can be used to reorder devices using ioinit but requires the standard BigBoy/BigGirl Policy statement:
"This technique will be changing the I/O config used by the kernel at bootup and mistakes (specifically to do with disk hardware) can render the system unusable and require the use of a recovery CDROM or a complete reinstall. A backup kernel will not fix I/O config file problems."
The technique is to change the file called /etc/ioconfig by using the ioinit command. Let's suppose we want to change the tape drive at 56/52.3.0 from instance 3 to instance 0, and change 56/52.1.0 from 0 to 3, thus swapping the instance numbers. Here are the steps:
# rmsf -vH 56/52.1.0
# rmsf -vH 56/52.3.0
Check the /dev/rmt diretory:
# ls /dev/rmt/
The device files for address 1 and 3 should be gone. Ignore any message from rmsf about trying to remove the driver (it can't do that anyway). Save a copy of the old ioconfig file:
# cp /etc/ioconfig /etc/ioconfig.old
Now create a file which assigns the desired instances, something like this:
56/52.1.0 tape 3
56/52.3.0 tape 0
The format is: hardware-path class instance
which can be found in the ioinit man page. This file should have all the changes you want to make. Now run ioinit to make the changes:
# ioinit -f /tmp/xx
where /tmp/xx is the file created above. If all is well, there will be no output. Run the same command again and it should report that the changes are already in place.
Now reboot. When the system comes back up, run the command:
# ioscan -knfC tape
and if no device files are shown, run the commands:
# insf -e -H 56/52.1.0
# insf -e -H 56/52.3.0
then run ioscan again. This should fix your instance numbers and device file names.
Bill Hassell, sysadmin
