AIX Boot Process.

First it check Hardware POST inventory.
Then ROS IPL checks user bootlist available devices. If a valid boot device not found then it boots from First boot device. ROS (Read Only Storage) this is a sample code which locate and load bootstrap code. It contains boot info.
Then S/W ROS locates , loads boot info and takes over control to BLV(Boot logical Volume)
Then control passed to kernel to begins to system initialization.
The system tested Hardware found in BLV & start the init process from /usr/lib/boot

With the Help of Init executes Rc.boot1 script

Init Start from Rc.boot 1.
Restbase command is called for copy the partial ODM into /dev/hd4 file system
Then cfgmgr –f called for config rules for ODM
Bootinfo –b cmd call for last boot device detection
So Phase 1 configuration methods results in the configuration of base devices into system.
Rc.boot 2 script call
Root VG will be activated with varyonvg cmd.
The /dev/hd4 file system checked and mount on / and also check for /dev/hd1 and mount on /usr
The /dev/hd9var file system checked and mount on /var. At same time copycore cmd check if dump occurred. If dump exists it will be copied from dump /dev/hd6 to default dir. /var/adm/ras then /var will be unmounted
Then swap or paging space will be turn on with the swapon cmd.
Mergedev cmd call & copied all /dev/ files from RAMFS to disk
As well as all customized ODM files from RAMFS are coped to disk.
Then /var mounted
At the end of rc.boot2 kernel removes from RAMFS.

Then init process is started Rc.boot3 script for remaining device configuration.
Then /dev/hd3 file system checked and mount on /tmp
RootVg will be synchronize with syncvg cmd.
Console is configured with cfgon cmd
Then savebase cmd saves boot customization details to be used on next boot.
Errdaemon and Syncd daemon will be started after 60 sec.
Remove /etc/nologin file
Then /etc/inittab file wiil be executes for start other process.