AIXBootLevel

How to display and set the AIX Boot Level

This is a request that comes back from time to time: "I need this AIX machine to boot in 64bits mode!". All right, all right, here is how to do it...

1. Displaying the current boot level (32/64 bits)

Use the bootinfo command, like this:

bash-3.00# bootinfo -K
64

Of course, the value returned indicates whether AIX is working in 32- or 64-bits mode.

2. Setting the boot level to 64 bits

To switch from 32-bit mode to 64-bit mode run the following commands, in the given order:

  1. ln -sf /usr/lib/boot/unix_64 /unix
  2. ln -sf /usr/lib/boot/unix_64 /usr/lib/boot/unix
  3. bosboot -ad /dev/ipldevice
  4. shutdown -Fr
  5. bootinfo -K (should now show 64)

(The above is copied straight from one of the references given below)

For instance:

# ln -sf /usr/lib/boot/unix_64 /unix
# ln -sf /usr/lib/boot/unix_64 /usr/lib/boot/unix
# bosboot -ad /dev/ipldevice

bosboot: Boot image is 32940 512 byte blocks.

# shutdown -Fr

SHUTDOWN PROGRAM
Fri Oct 31 11:51:38 CDT 2008
Wait for 'Rebooting...' before stopping.
Error logging stopped...
Advanced Accounting has stopped...
Process accounting stopped...
Stopping NFS/NIS Daemons
0513-004 The Subsystem or Group, nfsd, is currently inoperative.
0513-044 The biod Subsystem was requested to stop.
0513-044 The rpc.lockd Subsystem was requested to stop.
[...etc...]

One the machine has finished its reboot:

# uname -a && bootinfo -K
AIX galactus 3 5 00047689D600
64

3. Setting the boot level to 32 bits

To switch from 64-bit mode to 32-bit mode run the following commands, in the given order:

  1. ln -sf /usr/lib/boot/unix_mp /unix
  2. ln -sf /usr/lib/boot/unix_mp /usr/lib/boot/unix
  3. bosboot -ad /dev/ipldevice
  4. shutdown -Fr
  5. bootinfo -K (should now show 32)

See Also:

This is the page that gave me the most precise information:

The following page contains additional information, especially regarding the boot disk management: