LPI-1 Linux Certification – SysV Startup Sequence

SysV startup sequence

OS startup sequence (SysV) Debian Red Hat
At startup /sbin/init executes all instructions on /etc/inittab . This script at first switches to the default runlevel… id:2:initdefault: id:5:initdefault:
… then it runs the following script (same for all runlevels) which configures peripheral hardware, applies kernel parameters, sets hostname, and provides disks initialization… /etc/init.d/rcS /etc/rc.d/rc.sysinit or/etc/rc.sysinit
… and then, for runlevel N, it calls the script/etc/init.d/rc N (i.e. with the runlevel number as parameter) which launches all services and daemons specified in the following startup directories: /etc/rcN.d/ /etc/rc.d/rcN.d/

The startup directories contain symlinks to the init scripts in /etc/init.d/ which are executed in numerical order. Links starting with K are called with argument stop, links starting with S are called with argument start.

lrwxrwxrwx. 1 root root   14 Feb 11 22:32 K88sssd -> ../init.d/sssd
lrwxrwxrwx. 1 root root   15 Nov 28 14:50 K89rdisc -> ../init.d/rdisc
lrwxrwxrwx. 1 root root   17 Nov 28 15:01 S01sysstat -> ../init.d/sysstat
lrwxrwxrwx. 1 root root   18 Nov 28 14:54 S05cgconfig -> ../init.d/cgconfig
lrwxrwxrwx. 1 root root   16 Nov 28 14:52 S07iscsid -> ../init.d/iscsid
lrwxrwxrwx. 1 root root   18 Nov 28 14:42 S08iptables -> ../init.d/iptables

 

The last script to be run is S99local -> ../init.d/rc.local ; therefore, an easy way to run a specific program on boot is to add it to this script file.

/etc/init.d/boot.local   runs only at boot time, not when switching runlevel.

/etc/init.d/before.local (SUSE) runs only at boot time, before the scripts in the startup directories.

/etc/init.d/after.local     (SUSE) runs only at boot time, after the scripts in the startup directories.

 

Debian Red Hat
To add or remove services at boot sequence: update-rc.d service defaults update-rc.d -f service remove chkconfig –add service chkconfig –del service
Parameters supported by the init scripts
start Start the service Mandatory
stop Stop the service
restart Restart the service (stop, then start)
status Display daemon PID and execution status
force-reload Reload configuration if the service supports this option, otherwise restart the service
condrestart try-restart Restart the service only if already running Optional
reload Reload service configuration

/etc/init.d/service start

service service start    (Red Hat)                Start a service

rcservice start              (SUSE)

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