Dec 072006
 

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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

Install rcconf in Ubuntu

sudo 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) ...

Install file-rc in Ubuntu

sudo apt-get install file-rc

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

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 Posted by at 12:40 pm
  • http://www.clmitchell.net/ Quasaur

    I’m trying to get a consensus on the optimal order in which these services should be loaded…?

    Quasaur

  • Eugene

    “man update-rc.d” says:

    INSTALLING INIT SCRIPT LINKS

    A common system administration error is to delete the links with the thought that this will “disable” the service, i.e., that this will prevent the service from being started. However, if all links have been deleted then the next time the package is upgraded, the package’s postinst script will run update-rc.d again and this will reinstall links at their factory default locations. The correct way to disable services is to configure the service as stopped in all runlevels in which it is started by default. In the System V init system this means renaming the service’s symbolic links from S to K.

    EXAMPLES
    Example of disabling a service:
    update-rc.d -f foobar remove
    update-rc.d foobar stop 20 2 3 4 5 .

    It seems to me that correct way for disabling samba requires one more line: “update-rc.d samba stop 20 2 3 4 5 .” in addition to mentioned “update-rc.d samba remove” in the article above.

  • Ed

    Thank you for your nice explanation.
    I wrote a small tutorial about starting applications at boot time with root privileges in Debian Wheezy.

    You can find it in here:

    http://cosmolinux.no-ip.org/raconetlinux2/boot.html

    I wish it is useful to someone.

  • je

    When using update-rc.d, I needed to call it using sudo otherwise the script is not visible to “normal” users (it can be found in /usr/sbin).