Manage Linux init or
startup scripts
Init scripts are small shell programs that usually control
services, also known as daemons. Other applications for init
scripts involve simply controlling the state of something such
as hdparm (HDD sleep timeouts), iptables (loading firewall
rule-sets into the kernel) and setserial (COM port
configuration).The /etc/init.d directory contains the scripts
executed by init at boot time and when the init state.
Init scripts are also important during startup and shutdown
(simply “runlevel” changes on *nix systems). If you take a look
at the list of processes running on your machine (try ps auwx),
chances are that the process with the lowest PID is called
“init”. This is the parent of all processes; it’s the first
program the kernel starts when booting. init , which can be
found in /sbin/init, is responsible for getting the system up
and running after the kernel has finished booting.
There are three simple utilities to manage your startup or init
scripts
rcconf
update-rc.d
file-rc
Now we will see one by one with some examples
Rcconf
Rcconf allows you to control which services are started when the
system boots up or reboots. It displays a menu of all the
services which could be started at boot. The ones that are
configured to do so are marked and you can toggle individual
services on and off.This tool configures system services in
connection with system runlevels. It turns on/off services using
the scripts in /etc/init.d/. Rcconf works with System-V style
runlevel configuration. It is a TUI(Text User Interface)
frontend to the update-rc.d command.
Rcconf gets a list of services from /etc/init.d and looks in the
/etc/rc?.d directories to determine whether each service is on
or off.
If the number(NN of /etc/rc?.d/NNname) is not 20(default),
rcconf saves the service name and the number in /var/lib/rcconf/services
so as to be able to restore the service to its original
configuration.
Install rcconf in debian
#apt-get install rcconf
This will complete the installation now if you want to run this
application use the following command
rcconf
you should see the following screen here you can select which
services you want to run at boot time
Important Files
/var/lib/rcconf/services - The service number data file.
/var/lib/rcconf/lock - Lock file.
/var/lib/rcconf/guide.default - Guide File update-rcconf-guide
generates.
/var/lib/rcconf/guide - Guide File user(Administrator) can
define.
If you want to know more about rcconf check
man page
update-rc.d
install and remove System-V style init script links.update-rc.d
automatically updates the System V style init script links /etc/rcrunlevel.d/NNname
to scripts /etc/init.d/name. These are run by init when changing
runlevels and are generally used to start and stop system
services such as daemons. runlevel is one of the runlevels
supported by init, 0123456789S, and NN is the two-digit sequence
code used by init to decide which order to run the scripts in.
update-rc.d Syntax
update-rc.d [-n] [-f] name remove
update-rc.d [-n] name defaults [NN | NN-start NN-stop]
update-rc.d [-n] name start|stop NN runlevel runlevel start|stop
NN runlevel runlevel
When run with either the defaults, start, or stop options,
update-rc.d makes links /etc/rcrunlevel.d/[SK]NNname pointing to
the script /etc/init.d/name,If any files /etc/rcrunlevel.d/[SK]??name
already exist then update-rc.d does nothing. This is so that the
system administrator can rearrange the links, provided that they
leave at least one link remaining, without having their
configuration overwritten.
Available Options
-n Don’t do anything, just show what we would do.
-f Force removal of symlinks even if /etc/init.d/name still
exists.
update-rc.d Examples
Insert links using the defaults
#update-rc.d samba defaults
Equivalent command using explicit argument sets
#update-rc.d samba start 20 2 3 4 5 . stop 20 0 1 6 .
If you want to remove the script from the startup use the
following command
# update-rc.d -f samba remove
If you want to know more about update-rc.d check
man page
file-rc
Alternative boot mechanism using a single configuration file
This package provides an alternative mechanism to boot the
system, to shut it down and to change runlevels. The /etc/rc?.d/*
links will be converted into one single configuration file /etc/runlevel.conf
instead, which is easier to administrate than symlinks, and is
also more flexible. The package will automatically convert your
existing symlinks into the file method on installation, and
convert the file back into symlinks on removal. Both mechanisms
are compatible through /etc/init.d/rc, /etc/ init.d/rcS, /usr/sbin/update-rc.d,
and /usr/sbin/invoke-rc.d scripts.
Install file-rc in debian
# apt-get install file-rc
Reading Package Lists… Done
Building Dependency Tree… Done
The following packages will be REMOVED:
rcconf sysv-rc
The following NEW packages will be installed:
file-rc
WARNING: The following essential packages will be removed
This should NOT be done unless you know exactly what you are
doing!
sysv-rc (due to sysvinit)
0 upgraded, 1 newly installed, 2 to remove and 5 not upgraded.
Need to get 36.3kB of archives.
After unpacking 119kB disk space will be freed.
You are about to do something potentially harmful
To continue type in the phrase ‘Yes, do as I say!’
?]Yes, do as I say!
Get:1 http://mirror.ox.ac.uk stable/main file-rc 0.8.7 [36.3kB]
Fetched 36.3kB in 0s (231kB/s)
(Reading database … 20533 files and directories currently
installed.)
Removing rcconf …
dpkg: sysv-rc: dependency problems, but removing anyway as you
request:
sysvinit depends on sysv-rc (>= 2.85-2) | file-rc (>> 0.7.0);
however:
Package sysv-rc is to be removed.
Package file-rc is not installed.
Removing sysv-rc …
Selecting previously deselected package file-rc.
(Reading database … 20507 files and directories currently
installed.)
Unpacking file-rc (from …/archives/file-rc_0.8.7_all.deb) …
Setting up file-rc (0.8.7) …
Configuration file for file-rc is located at /etc/runlevel.conf.If
you want to know the default configuration file check
here
Examples
#
05 - 0 /etc/init.d/halt
05 - 1 /etc/init.d/single
05 - 6 /etc/init.d/reboot
10 0,1,6 2,3,4,5 /etc/init.d/sysklogd
12 0,1,6 2,3,4,5 /etc/init.d/kerneld
[…]
89 0,1,6 2,3,4,5 /etc/init.d/cron
99 - 2,3,4,5 /etc/init.d/rmnologin
99 0,1,6 2,3,4,5 /etc/init.d/xdm
If you want to know more details about file-rc check
man page
