aix boot sequence

STEP-1          POST(power on self test)

it's purpose is to verify that the basic hardware is in functional state.
     the memory,communication and audio devices are all initialized.

STEP 2           System ROS (Read only storage)

system ROS is necessary for AIX 5L version 5.3 to boot, but it doesn't built the data structures required for booting.

it will locate the bootstrap code.

system ROS contains generic boot information and is OS independent.

STEP 3             SOFTWARE ROS(also called bootstrap)

Software ROS forms an IPL(initial program load) block ,that takes control and builds AIX5L specific boot information.

A special filesystem called RAMFS filesystem is created in memory.


softwareROS locates and loads Boot logical volume(BLV)in ram.

• contents of BLV

               1. AIX 5L kernel
               2. reduced version of ODM
               3. rc.boot script
               4. boot commands called during boot process like bootinfo,cfgmgr.

AIX 5L kernel is loaded. the kernel will complete the boot process and starts the init process.

  LED =0299

now, rc.boot script will be called three times,and is passed through different parameters each time.


BOOT PHASE 1

Init process started from RAMFS execute the boot script rc.boot1

if init fails LED will display c06

"restbase "command  -- copies partial image of ODM  from BLV to ramfs.

LED =548 if successful

"cfgmgr -f" command

Reads the config-rules class from the reduced ODM.
                                             in this class, devices with attribute phase=1 are considered base devices
base devices are all devices that are necessary to access rootvg.

"bootinfo -b" command

determines the last boot device

LED =511 ,if successful

 BOOT PHASE 2




in this phase,the rc.boot script is passed  with parameter 2.

"ipl-varyonvg rootvg" command

rootvg is activated.

LED =517 ,if sucessfull
LED =552,554 or 556 ,if boot process is halted.

root(/) filesystem (hd4) is checked using  "fsck -f"  to verify whether the filesystem was unmounted clearly before the last shutdown.

/dev/hd4 is temporarly mounted in RAMFS


LED=557,if fails

/user,/var are verified using  " fsck -f"  command and then mounted temporarily
LED =518 ,if /usr fails tomount 

"copycore" command

checks if a dump occurred. if it is copied ffrom default dump device /dev/hd6 to the default copy directory/var/adm/ras/

afterward /var and /usr are unmounted.

the primary paging space from rootvg ,/dev/hd6 is activated.


"mergedev " process is called and all /dev files from REAMFS are copied to disk

All customized ODM files RAMFS are copied to disk.
                                                   both ODM versions from hd4 and hd5 are synchronized.

finally root file system from rootvg is mounted over the original mountpoint from RAMFS.

/var and /usr are also mounted to their mount-point.

BOOT PHASE 3

After boot phase 2, rootvg is activated.

Init process is started . it reads the/etc/inittab file and calls rc.boot with arguement 3
/tmp filesystem is mountd.

"syncvg" command  - rootvg is synchronized . it runs as backgroundprocess. it checks all stale partitions from rootvg and updates it.
LED =553,if successfull.

"cfgmgr" command

if booted in
  normal mode - option is p2
 service boot - option is p3.

it reads the config-rules class from ODM and calls all methods correponding to either phase=2 or phase=3

all other devices ,that are not base devices are configured this time

"cfgcon "command

console is configured by calling the cfgcon command.
     after the configuration of the console,boot messages are sent to the consoleif no STDOUT direction is made.
         all missed messages can be found in /var/adm/ras/conslog


LED C31 - console not yet configured.
        C33 - console is tty.
        C34 - console is a file on disk.

"savebase" command

synchronization of ODM  in BLV wiith the ODM  in root filesystem is done.

syncd daemon and errdaemon are started.
LED display is turned off.

if /etc/nologin exists,it is removed.