/etc/inittab explanation

/etc/inittab file

init:2:initdefault:
brc::sysinit:/sbin/rc.boot 3 >/dev/console 2>&1 # Phase 3 of system boot
powerfail::powerfail:/etc/rc.powerfail 2>&1 | alog -tboot > /dev/console # Power Failure Detection
mkatmpvc:2:once:/usr/sbin/mkatmpvc >/dev/console 2>&1
atmsvcd:2:once:/usr/sbin/atmsvcd >/dev/console 2>&1

Inittab file lists the process that init starts, and it also specifies when to start them .

There are 4 fields in the inittab file

id   – 14 characters that identify the process. Terminals use their logical device name as an identifier
runlevel – Specified in which run level this particular process runs.
The valid run-levels could be 0-9
The default run-level in AIX is 2 multi-user mode.
Action –  How to treat the process. Possible values are
i) sysinit – processes to run the system initialization
ii) respawn – If the process is not started already, start it
iii) off – Do not run the process
iv) once – start the process and do not restart if it stops
v) wait – start the process and wait before going to the next line.

Command –  The AIX command to run to start the process.

Few Important Points on /etc/inittab

*  “telinit”  command can be used to change the run-level or to  force to re-read the /etc/inittab after any changes (telinit q)
*  The following are the commands used for inittab file configuration
i) mkitab – command to create new entry
ii) chitab – command to change the existing entry
iii) rmitab – command to remove the existing entry
iv) lsitab – command to list the entries in /etc/inittab

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