Inittab Queries

[Dinesh_15]

Hi Folks

Again ..

Can any body explain the following entries in my HP 11i /etc/inittab file.




stty::sysinit:/sbin/stty 9600 clocal icanon echo opost onlcr ixon icrnl ignpar
vxen::bootwait:/sbin/fs/vxfs/vxenablef -a

vol1::sysinit:/sbin/init.d/vxvm-sysboot /dev/console 2>&1 ##vxvm

vol2::sysinit:/sbin/init.d/vxvm-startup start /dev/console 2>&1 ##vxvm

brc1::bootwait:/sbin/bcheckrc /dev/console 2>&1 # fsck, etc.

link::wait:/sbin/sh -c "/sbin/rm -f /dev/syscon; \
/sbin/ln /dev/systty /dev/syscon" >/dev/console 2>&1


sqnc::wait:/sbin/rc /dev/console 2>&1 # system init



#ttp1:234:respawn:/usr/sbin/getty -h tty0p1 9600
krsd:123456:respawn:/sbin/krsd -i

sfd:123456:respawn:/sbin/sfd

ems1::bootwait:/sbin/rm -f /etc/opt/resmon/persistence/runlevel4_flag

ems2::bootwait:/sbin/cat /etc/opt/resmon/persistence/reboot_flag


ems3:3456:wait:/sbin/sh -c "/usr/bin/touch /etc/opt/resmon/persistence/runlevel4_flag; /usr/bin/chmod 644 /etc/opt/resmon/persistenc
e/runlevel4_flag"


ems4:3456:respawn:/etc/opt/resmon/lbin/p_client

cim1:3456:respawn:/opt/wbem/sbin/cimserverd

#ups::respawn:rtprio 0 /usr/lbin/ups_mond -f /etc/ups_conf

a0:234:respawn:/usr/sbin/getty -h -t 40 ttyd1p2 19200m
#


Sorry for posting the big question

Rgds
Dinu

[Bharat Katkar]

HI Dinu,

a0:234:respawn:/usr/sbin/getty -h -t 40 ttyd1p2 19200m

first thing is : is a delimiter and then we have different fields separated by colon delimiter.

Field 1: Process ID
Fiedl 2: Process Run Levels
Field 3: PRocess STate
Field 4: Process

Respawn is Start the process and restart if it dies.

Hope that helps,
Regards,

[Dinesh_15]

Hi Bharath

Thanks for the answer.

In fact I want other details..Let me be specific..I know the fileds and their delemeters..

But I want what the process as mentioned in the inittab files does..
Eg
a0:234:respawn:/usr/sbin/getty -h -t 40 ttyd1p2 19200m

In this system is running the getty process and process never dies, as respawn is there..
Like that I want the details for the other entries.. Can you please have a try..

or anybody else


Please

Rgds
Dinu

[Bharat Katkar · Accepted solution]

Hi Dinu,

a0:234:respawn:/usr/sbin/getty -h -t 40 ttyd1p2 19200m

Now let us take this entry as an example. Now here the process is getty with some arguments. Then a0 is the process ID.

234 this means this process can be started in any of the run levels 2 3 and 4.
i.e. init 2, init 3 and init 4 will make sure that getty is started and running.

The next field os ProcessState so it is not actually state but the action taken by init on that process. This is the most important to understand and it has various values as given below:


respawn:
If the process does not exist, then start the process; do not wait for its termination (continue scanning the inittab file), and when the process dies, restart the process. If the process currently exists, do nothing and continue scanning the inittab file.

wait:
When init enters the run level that matches the entry's rstate, start the process and wait for its termination. All subsequent reads of the inittab file while init is in the same run level cause init to ignore this entry.

once:
When init enters a run level that matches the entry's rstate, start the process, do not wait for its termination. When it dies, do not restart the process. If init enters a new run level and the process is still running from a previous run level change, the program is not restarted.

boot:
The entry is to be processed only at init's boot-time read of the inittab file. init is to start the process and not wait for its termination; when it dies, it does not restart the process. In order for this instruction to be meaningful, the rstate should be the default or it must match init's run level at boot time. This action is useful for an initialization function following a hardware reboot of the

system.
bootwait:
The entry is to be processed the first time init goes from single-user to multi-user state after the system is booted. (If initdefault is set to the process runs right after the boot.)

init:
starts the process, waits for its termination and, when it dies, does not restart the process.

powerfail:
Execute the process associated with this entry only when init receives a power fail signal, SIGPWR (see signal(3C)).

powerwait:
Execute the process associated with this entry only when init receives a power fail signal, SIGPWR, and wait until it terminates before continuing any processing of inittab.

off:
If the process associated with this entry is currently running, send the warning signal SIGTERM and wait 5 seconds before forcibly terminating the process with the kill signal SIGKILL. If the process is nonexistent, ignore the entry.

ondemand:
This instruction is really a synonym for the respawn action. It is functionally identical to respawn but is given a different keyword in order to divorce its association with run levels. This instruction is used only with the a, b or c values described in the rstate field.

initdefault:
An entry with this action is scanned only when init is initially invoked. init uses this entry to determine which run level to enter initially.It does this by taking the highest run level specified in the rstate field and using that as its initial state. If the rstate field is empty, this is interpreted as 0123456 and init will enter run level 6. This will cause the system to loop (it will go to firmware and reboot continuously). Additionally, if init does not find an initdefault entry in inittab, it requests an initial run level from the user at reboot time.

sysinit:
Entries of this type are executed before init tries to access the console (that is, before the Console Login: prompt). It is expected that this entry will be used only to initialize devices that init might try to ask the run level question. These entries are executed and init waits for their completion before continuing.

I think this should be sufficient for you to understand inittab.
Regards,

[Dinesh_15]

Hi Bharat

Splendid ...

Thanks for the nice explanation..
Hope u will not mind if I trouble you more on this with little bit of digging.. Newbie please help
..
1)Always there are more than one process with wait status.. Does this mean that these are run sequentilally. i.e first process with wait status and the second, third like that..
2) link::wait:/sbin/sh -c "/sbin/rm -f /dev/syscon; \
/sbin/ln /dev/systty /dev/syscon" >/dev/console 2>&1

In above statement why the system console file( I hope so) is deleted first and then recreated with link again?
3):/sbin/sfd-----
what the sfd process does?

4)stty::sysinit:/sbin/stty 9600 clocal icanon echo opost onlcr ixon icrnl ignpar ---What is this nprocess

Please answer this

Rgds
Dinu

[Dinesh_15]

Hi All

Can anybody answer for the above


Rgds
Dinu

[Sridhar Bhaskarla]

Hi Dinesh,

1. 'wait' has nothing to do with the hierarchy of the entries in /etc/inittab.
2. syscon is a logical console that is linked to the physical console systty. In order to ensure that the console works correctly, each time it is started by 'init' process, it is freshly linked. The state 'wait' along with no rstate definition means init needs to re-start it as soon as there is a change in the run level.
3. sfd command creates special files dynamically with 'insf' command.
4. It's not really a process. It sets the characterstics of the console.

-Sri