Assuming you have the proper hardware...
How would I know if I am running a 32-bit kernel or 64-bit kernel?
To display if the kernel is 32-bit enabled or 64-bit enabled, type:
bootinfo -K
How do I know if I am running a uniprocessor kernel or a multiprocessor kernel?
/unix is a symbolic link to the booted kernel. To find out what kernel mode is running, enter ls -l /unix and see what file /unix it links to. The following are the three possible outputs from the ls -l /unix command and their corresponding kernels:
/unix -> /usr/lib/boot/unix_up # 32 bit uniprocessor kernel
/unix -> /usr/lib/boot/unix_mp # 32 bit multiprocessor kernel
/unix -> /usr/lib/boot/unix_64 # 64 bit multiprocessor kernel
Note:
AIX 5L Version 5.3 does not support a uniprocessor kernel.
How can I change from one kernel mode to another?
During the installation process, one of the kernels, appropriate for the AIX version and the hardware in operation, is enabled by default. Let us use the method from the previous question and assume the 32-bit kernel is enabled. Let us also assume that you want to boot it up in the 64-bit kernel mode. This can be done by executing the following commands in sequence:
ln -sf /usr/lib/boot/unix_64 /unix
ln -sf /usr/lib/boot/unix_64 /usr/lib/boot/unix
bosboot -ad /dev/hdiskxx
shutdown -r
The /dev/hdiskxx directory is where the boot logical volume /dev/hd5 is located. To find out what xx is in hdiskxx, run the following command:
lslv -m hd5
Note:
In AIX 5.2, the 32-bit kernel is installed by default. In AIX 5.3, the 64-bit kernel is installed on 64-bit hardware and the 32-bit kernel is installed on 32-bit hardware by default.