IBM AIX - Boot Process

AIX Boot Process

1. When the server is Powered on Power on self test(POST) is run and checks the hardware
2. On successful completion on POST Boot logical volume is searched by seeing the bootlist
3. The AIX boot logical contains AIX kernel, rc.boot, reduced ODM & BOOT commands. AIX kernel is loaded in the RAM.
4. Kernel takes control and creates a RAM file system.
5. Kernel starts /etc/init from the RAM file system
6. init runs the rc.boot 1 ( rc.boot phase one) which configures the base devices.
7. rc.boot1 calls restbase command which copies the ODM files from Boot Logical Volume to RAM file system
8. rc.boot1 calls cfgmgr –f command to configure the base devices
9. rc.boot1 calls bootinfo –b command to determine the last boot device
10. Then init starts rc.boot2 which activates rootvg
11. rc.boot2 calls ipl_varyon command to activate rootvg
12. rc.boot2 runs fsck –f /dev/hd4 and mount the partition on / of RAM file system
13. rc.boot2 runs fsck –f /dev/hd2 and mounts /usr file system
14. rc.boot2 runs fsck –f /dev/hd9var and mount /var file system and runs copy core command to copy the core dump if available from /dev/hd6 to /var/adm/ras/vmcore.0 file. And unmounts /var file system
15. rc.boot2 runs swapon /dev/hd6 and activates paging space
16. rc.boot2 runs migratedev and copies the device files from RAM file system to /file system
17. rc.boot2 runs cp /../etc/objrepos/Cu* /etc/objrepos and copies the ODM files from RAM file system to / filesystem
18. rc.boot2 runs mount /dev/hd9var and mounts /var filesystem
19. rc.boot2 copies the boot log messages to alog
20. rc.boot2 removes the RAM file system
21. Kernel starts /etc/init process from / file system
22. The /etc/init points /etc/inittab file and rc.boot3 is started. Rc.boot3 configures rest of the devices
23. rc.boot3 runs fsck –f /dev/hd3 and mount /tmp file system
24. rc.boot3 runs syncvg rootvg &
25. rc.boot3 runs cfgmgr –p2 or cfgmgr –p3 to configure rest of the devices. Cfgmgr –p2 is used when the physical key on MCA architecture is on normal mode and cfgmgr –p3 is used when the physical key on MCA architecture is on service mode.
26. rc.boot3 runs cfgcon command to configure the console
27. rc.boot3 runs savebase command to copy the ODM files from /dev/hd4 to /dev/hd5
28. rc.boot3 starts syncd 60 & errordaemon
29. rc.boot3 turn off LED’s
30. rc.boot3 removes /etc/nologin file
31. rc.boot3 checks the CuDv for chgstatus=3 and displays the missing devices on the console
32. The next line of Inittab is executed

/etc/inittab file format: identifier:runlevel:action:command

Mkitab-----Add records to the /etc/inittab file

Lsitab-----List records in the /etc/inittab file

Chitab-----changes records in the /etc/inittab file

Rmitab-----removes records from the /etc/inittab file