When you boot the system or change run levels with the init or shutdown command, the init daemon starts processes by reading information from the /etc/inittab file. This file defines three important items for the init process:
The system's default run level
What processes to start, monitor, and restart if they terminate
What actions to take when the system enters a new run level
Each entry in the /etc/inittab file has the following fields:
id:rstate:action:process
The following table describes the fields in an inittab entry.
Table 11–2 Fields Descriptions for the inittab File
Field |
Description |
---|---|
id |
Is a unique identifier for the entry. |
rstate |
Lists the run levels to which this entry applies. |
action |
Identifies how the process that is specified in the process field is to be run. Possible values include: initdefault, sysinit, boot, bootwait, wait, and respawn. initdefault identifies the default run level. For a description of the other action keywords, see inittab(4). |
process |
Defines the command or script to execute. |
The following example shows an annotated default inittab file that is installed with the Solaris release:
1 ap::sysinit:/sbin/autopush -f /etc/iu.ap 2 ap::sysinit:/sbin/soconfig -f /etc/sock2path 3 fs::sysinit:/sbin/rcS sysinit >/dev/msglog 2<>/dev/msglog </dev/console 4 is:3:initdefault: 5 p3:s1234:powerfail:/usr/sbin/shutdown -y -i5 -g0 >/dev/msglog 2<>/dev/... 6 sS:s:wait:/sbin/rcS >/dev/msglog 2<>/dev/msglog </dev/console 7 s0:0:wait:/sbin/rc0 >/dev/msglog 2<>/dev/msglog </dev/console 8 s1:1:respawn:/sbin/rc1 >/dev/msglog 2<>/dev/msglog </dev/console 9 s2:23:wait:/sbin/rc2 >/dev/msglog 2<>/dev/msglog </dev/console 10 s3:3:wait:/sbin/rc3 >/dev/msglog 2<>/dev/msglog </dev/console 11 s5:5:wait:/sbin/rc5 >/dev/msglog 2<>/dev/msglog </dev/console 12 s6:6:wait:/sbin/rc6 >/dev/msglog 2<>/dev/msglog </dev/console 13 fw:0:wait:/sbin/uadmin 2 0 >/dev/msglog 2<>/dev/msglog </dev/console 14 of:5:wait:/sbin/uadmin 2 6 >/dev/msglog 2<>/dev/msglog </dev/console 15 rb:6:wait:/sbin/uadmin 2 1 >/dev/msglog 2<>/dev/msglog </dev/console 16 sc:234:respawn:/usr/lib/saf/sac -t 300 17 co:234:respawn:/usr/lib/saf/ttymon -g -h -p "`uname -n` console login: " -T terminal-type -d /dev/console -l console -m ldterm,ttcompat |
Initializes STREAMS modules
Configures socket transport providers
Initializes file systems
Defines default run level
Describes a power fail shutdown
Defines single-user level
Defines run level 0
Defines run level 1
Defines run level 2
Defines run level 3
Defines run level 5
Defines run level 6
Defines an unused level, firmware
Defines an unused level, off
Defines an unused level, reboot
Initializes Service Access Controller
Initializes console and identifies the terminal type
The init process is started and reads the /etc/default/init file to set any environment variables. By default, only the TIMEZONE variable is set.
Then init reads the inittab file and does the following:
Identifies the initdefault entry, which defines the default run level (3).
Executes any process entries that have sysinit in the action field so that any special initializations can take place before users login.
Executes any process entries that have a 3 in the rstate field, which matches the default run level, 3.
For a detailed description of how the init process uses the inittab file, see init(1M).
The following table describes the keywords used for run level 3's action field.
Table 11–3 Run Level 3 Action Keyword Descriptions
Key Word |
Description |
---|---|
powerfail |
Starts the process when the init process receives a power failure signal |
respawn |
Starts the process and restarts it when it dies |
wait |
Starts the process and waits for it to finish before going on to the next entry for this run level |
The following table describes the processes (or commands) that are executed at run level 3.
Table 11–4 Command Descriptions for Run Level 3
Command or Script Name |
Description |
---|---|
/usr/sbin/shutdown |
Shuts down the system. The init process runs the shutdown command only if the system has received a power fail signal. |
/sbin/rcS |
Checks and mounts root (/), /usr, /tmp, /var, /var/adm, and /var/run file systems. |
/sbin/rc2 |
Starts the standard system processes and brings the system up into run level 2 (multiuser level). |
/sbin/rc3 |
Starts NFS resource sharing for run level 3. |
/usr/lib/saf/sac -t 30 |
Starts the port monitors. This process is restarted if it fails. |
/usr/lib/saf/ttymon -g -h -p "`uname -n` console login: " -T terminal_type -d /dev/console -l console |
Starts the ttymon process that monitors the console for login requests. This process is restarted if it fails. The terminal_type on a SPARC based system is sun. The terminal_type on an x86 based system is AT386. |