System Startup Procedure

There are 3 Phases involved in AIX startup procedure, they are

i) ROS (Read Only Storage) Phase
ii) Device Configuration Phase
iii) Init Phase

ROS (Read Only Storage) Phase

i) Hardware devices are verified and checked for possible issues — POST
ii) Bootlist is found — System ROS detects the first boot device in the bootlist specified
iii) Boot image is loaded into the Memory – First 512 bytes block (sector) contains the bootstrap code of the hdisk is loaded into RAM
iv) Initialization starts – Bootstrap code locates BLV (/hd5) from the disk.

During the above process the following activities has been performed

  •  BLV contains the kernel, boot commands, reduced ODM and rc.boot scripts.
  • BLV get uncompressed in RAM and release the kernel.
  • Then AIX kernel gets control.
  • AIX kernel creates temporary RAMFS with /, /etc , /usr /dev , /mnt etc.,
  • Kernel starts the init process from BLV in the RAM.
  • Init executes rc.boot script from the BLV in the RAM. There are 3 rc.boot scripts rc.boot.1 , rc.boot.2 and rc.boot.3

ii) Base Device Configuration Phase

i) All devices are configured with “cfgmgr” command
ii) init process executes “rc.boot.1” from RAMFS
iii) “restbase” command copies reduced ODM from BLV to RAMFS
iv) “cfgmgr” will run and configure all the devices

i)  LV s are varied on

  • rc.boot.2 is executed
  • varyon the rootvg
  • run fsck on /,/usr./var and mount the same to RAMFS

ii) Paging is started

  • “copycore”   command checks the occurrence of the dump and copy the same from the /var/ras/adm
  • unmount the /var and activate the paging
  • mount /var
  • now /, /usr, /var are mounted on rootvg in disk .

iii) /etc/inittab is processed

  • Kernel removes RAMFS
  • init process is started from / in rootvg
  • /etc/init starts /etc/inittab and runs /sbin/rc.boot3
  • /etc/inittab decides the run level.
  • Run the fsck on /tmp and mount the same
  • syncvg for rootvg and reports the stale PP s.
  • Use “savebase”  command to save the customized data to the BLV.
  • Exit the rc scripts

iv) Relevant services according to the run level starts, srcmstr daemon (System Resource controller) and start the relevant subsystems

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