AIX boot Process

AIX Boot process .

1)you power on the AIX server
2)The POST ( Power On Self Test ) will be done .

It varifies the basic hardware, Check is it is in functional state or not.
The memory,keyboard, communication and audio devices are also initialized
we can see the icons on the the screen
3)This is the correct step where you can select the boot list by pressing function key
4)The LED values displayed during this phase are model specific.
5)The system read only Storage is specific to the system type. It is the one which is used to boot the system ,but it will not contain any data structure.
This ROS contain only the location to the bootstrap .
It will load the the Bootstrap .
ROS contains generic boot information and is operating system independent.
6)The bootstrap also called as software ROS.
This bootstrap contains IPL ( Initial Program loader )
Which is used to build AIX specific boot information.
Software RS is AIX 5L information created based on machine type and is responsible for completing machine preparation to enable it to start AIX 5L kernel.
7)A special file system will be created in memory called RAMFS ,
8)Bootstrap locates and loads the BLV in to memory and gives control to BLV
9)BLV ( boot Logical volume )
The complete list of files that are there in BLV can be found in /usr/lib/boot.
The AIX 5L kernel
The boot command called during the booting process like cfgmgr, bootinfo
The reduced version of ODM ( object Data Manager ),
The hd4 contains all the device spcific methods info , but before loading we need
some devices like keyboard more . So the BLV contains methods to load those
devices .
The rc.boot program

10)Then BLV loads complete AIX kernel,and gives control. LED 0299.
11)All Previous LED values are hardware specific.
12)Complete the boot process by lading all the devices.
13) LED codes displayed during this stage will be generic AIX 5L specific
14)Now Init process will be started
15)Till now the rootvg is not mounted.
16)Till now the rc.boot script called 3 tiles with 1, 2, 3 arguments.
We call this as the 3 phases of initialization .
17)rc.boot 1 -----> Boot phase 1.
a) The init process started from RAMFS executes the boot script rc.boot 1
b) If init process fails the LED code will be c06.
c) restbase will be called in this phase to copy the partial copy of the ODM from BLV to RMFS.
d) IF successful then shows 510 , if fails 548 on LED.
e) After this, the cfgmgr -f command reads the Config_Rules class from the reduced ODM

f) devices with the attribute phase=1 are considered base devices. Base devices are all
devices that are necessary to access rootvg.
g) Like all the devices that are there to acced rootvg from mothere board to Hard disk
will be activated.
h) The bootinfo -b will be called to determine the last boot device .

18)rc.boot 2 -----------> Boot Phase 2.

a) The rootvg volume group is varied on with the special version of the varyonvg
ipl_varyon command
b) If this command is successful the LED value will be 517.
c) If failed LED value will be 552, 554, 556 and the boot process is halted.
d) Root file system hd4 is checked using the fsck -f command. This will verify
whether the lass shutdown was clean .
e) if command fails system will show 555
f) The root file system (/dev/hd4) is mounted on a temporary mount point /mnt in
g) If this fails, 557 will appear in the LED display.
h)The /usr file system is verified using the fsck -f command and then mounted.
i) If fails then LED value will be 518.
j) The /var file system is verified using the fsck -f command and then mounted.
k) Then copycore command will check for dumps if exist then copy form the
default dump device /dev/hd6 to default directory /var/adm/ras.
l) After this /var is unmounted
m) The primary paging space from rootvg, /dev/hd6, will be activated.
n) The mergedev process is called and all /dev files from the RAM file system
copied on to disk.
o) All customized ODM files from the RAM file system are copied to disk.
p) Both ODM versions from hd4 and hd5 are now synchronized.
q) Finally, the root file system from rootvg (disk) is mounted over the root
filesystem from the RMFS.
r) The mount points for the rootvg file system is available now.
s) then /var /usr are mounted again on normal mount points.
t) There is no console available at this all the messages are copied to alog.
u) alog is program that maintain all the logs.

19) rc.boot 3 -----------> Boot Phase 3.

a) /etc/init program starts and reades the /etc/inittab callas rc.boot with 3.
b) The /tmp file system is mounted.
c) The rootvg is synchronized by calling the syncvg command and launching it as
as a background process.
d) As a result all stale partitions from rootvg are the LEC value is 553.
e) At this stage, the cfgmgr command is called: if the system is booted in normal
mode with the option -p2.
if it booted in service mode the cfgmgr is called with -p3 option.
f) The cfgmgr command reads the Config_rules file from oDM and calls all
methods corresponding to either phase=2 or phase=3.
g) All the devices that are not basic devices are initialized.
h) The console is configured by calling the cfgcon command , Now boot
messages are sent to console .
i) if there is any problem in console the messages are stored in

20)Finally the syncronization of ODM done from BLV with /root filesystem is done. Savebase command.
21)he syncd daemon and errdemon are started.
22)LED display went off.
23)If the file /etc/nologin exists, it will be removed.
24)If there are devices marked as missing in CuDv a message is displayed on the console
25)The message System initialization completed is sent to the console.
The execution of rc.boot is has completed the process init will continue the next command from /etc/inittab .

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