In AIX its important to know exactly which “kernel mode” we are using as its useful for server security and performance. Basically in AIX the symbolic link is used to define the “kernel mode” which is different as compare to other operating systems. In AIX three main “kernel mode” is available on every server, we can set the “kernel mode” as per requirement, The “kernel mode” symbolic link defined under the /unix directory , therefore we can change the “kernel mode” by removing the symbolic present under the /unix directory and create the new symbolic link as per “kernel mode” we want to set.
To check the “kernel mode”, simply login into the Server as a root user and run the following commands from the shell.
ls -l /unix
It will show the following three possible outputs as per “kernel mode” defined on server.
/unix -> /usr/lib/boot/unix_up # The 32 bit uniprocessor kernel
/unix -> /usr/lib/boot/unix_mp # The 32 bit multiprocessor kernel
/unix -> /usr/lib/boot/unix_64 # The 64 bit multiprocessor kernel
For example, if you want to change the “kernel mode” from 32 bit “kernel mode” to 64 bit “kernel mode”, then refer to the following command one by one but make sure that you know exactly which command you are running else it will cause you many problem.
ln -sf /usr/lib/boot/unix_64 /unix
# It will create new symbolic link for 64 bit “kernel mode”
ln -sf /usr/lib/boot/unix_64 /usr/lib/boot/unix
# It will create symbolic link in boot logical volume
bosboot -ad /dev/hdiskxxx
# It will create complete boot image ( -a ) and define boot device ( -d )
shutdown -r
# It will initiate system reboot through the shutdown command.
The /dev/hdiskxx directory is a directory under which the complete boot image will be created. To find out what xxx is in hdiskxx, run the following command.
lslv -m hdxxx
For example dev/hdisk is /dev/hd3, then command will be
lslv -m /dev/hd3
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