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When your machine turns on or reboots, you want certain things to happen automatically. If the 'machine' is a web server hosting websites defined by [[Apache]] and also a database server running [[MySQL]], then naturally you would want Apache and MySQL to start automatically. In SysV-style systems that still use <code>init</code> and the rc.d run levels, you can use either <code>chkconfig</code><ref>http://linuxcommand.org/man_pages/chkconfig8.html</ref> (RedHat and derivatives) or <code>sysv-rc-conf</code> for Debian variants to make that permanent.

When your machine turns on or reboots, you want certain things to happen automatically. If the 'machine' is a web server hosting websites defined by [[Apache]] and also a database server running [[MySQL]], then naturally you would want Apache and MySQL to start automatically. In SysV-style systems that still use <code>init</code> and the rc.d run levels, you can use either <code>chkconfig</code><ref>http://linuxcommand.org/man_pages/chkconfig8.html</ref> (RedHat and derivatives) or <code>sysv-rc-conf</code> or <code>update-rc.d</code><ref>http://manpages.ubuntu.com/manpages/precise/man8/update-rc.d.8.html</ref>for Debian variants to make that permanent. The old SysV style init has now largely been replaced by <code>'''systemd'''</code>, so this article is just to guide you through some of the equivalents across multiple ways of doing init.

=== List services ===

So what are the services controlled by 'init' scripts?

So what are the services controlled by init<ref>http://manpages.ubuntu.com/manpages/trusty/man5/init.5.html</ref><ref>http://manpages.ubuntu.com/manpages/trusty/man8/init.8.html</ref> scripts?

<~~source~~ lang="bash">

# the easy way

# the easy way (if somewhat non-specific)

ls -l /etc/rc.d/init.d/

# using chkconfig

# On Ubuntu 14.04 you'll have the 'service' command

# service --status-all runs all init scripts, in alphabetical order, with the status command. This option only calls status for sysvinit jobs

service --status-all

# upstart jobs can be queried in a similar manner with initctl list

initctl list

# on older Ubuntu like 14.04, you probably also have update-rc.d, but that doesn't have a 'list' command

# You could 'manually' search all the init scripts for the right runlevel

grep -i 'runlevel' /etc/init/*| awk '!/#/ && /start on/ && /2/ {gsub("/"," "); print $0 }' | cut -d ' ' -f4-

# or

grep -i 'runlevel' /etc/init/* | awk '/start on/ && /2/ {gsub("/"," "); gsub(":", " ");gsub(".conf"," "); print $3 }'

# the RedHat way (using chkconfig)

chkconfig --list

# for newer systemd controlled systems

systemctl list-units

</~~source~~>

</syntaxhighlight>

Here is an example list of the services you might find on your machine:

# NetworkManager

Line 130:

Line 140:

=== Enable/Disable/Start/Stop/Status a service ===

<~~source~~ lang="bash">

# for older systems using System V style init

chkconfig apache on|off|start|stop|status

# for newer systemd controlled systems

systemctl enable|disable|start|stop|status <servicename>.service

</~~source~~>

</syntaxhighlight>

== SystemD targets ==

To switch to single-user mode, what used to be called '''runlevel 1''', on a modern Linux running SystemD, you would now use the command:

<code>sudo systemctl isolate rescue.target</code>

courtesy of https://askubuntu.com/questions/788323/how-do-i-change-the-runlevel-on-systemd

== More ==

@@ Line 1: / Line 1: @@
-When your machine turns on or reboots, you want certain things to happen automatically.  If the 'machine' is a web server hosting websites defined by [[Apache]] and also a database server running [[MySQL]], then naturally you would want Apache and MySQL to start automatically.  In SysV-style systems that still use <code>init</code> and the rc.d run levels, you can use either <code>chkconfig</code><ref>http://linuxcommand.org/man_pages/chkconfig8.html</ref> (RedHat and derivatives) or <code>sysv-rc-conf</code> for Debian variants to make that permanent.
+When your machine turns on or reboots, you want certain things to happen automatically.  If the 'machine' is a web server hosting websites defined by [[Apache]] and also a database server running [[MySQL]], then naturally you would want Apache and MySQL to start automatically.  In SysV-style systems that still use <code>init</code> and the rc.d run levels, you can use either <code>chkconfig</code><ref>http://linuxcommand.org/man_pages/chkconfig8.html</ref> (RedHat and derivatives) or <code>sysv-rc-conf</code> or <code>update-rc.d</code><ref>http://manpages.ubuntu.com/manpages/precise/man8/update-rc.d.8.html</ref>for Debian variants to make that permanent.  The old SysV style init has now largely been replaced by <code>'''systemd'''</code>, so this article is just to guide you through some of the equivalents across multiple ways of doing init.
 === List services ===
-So what are the services controlled by 'init' scripts?
+So what are the services controlled by init<ref>http://manpages.ubuntu.com/manpages/trusty/man5/init.5.html</ref><ref>http://manpages.ubuntu.com/manpages/trusty/man8/init.8.html</ref> scripts?
-<source lang="bash">
+<syntaxhighlight lang="bash">
-# the easy way
+# the easy way (if somewhat non-specific)
 ls -l /etc/rc.d/init.d/
-# using chkconfig
+# On Ubuntu 14.04 you'll have the 'service' command
+# service --status-all runs all init scripts, in alphabetical order, with the status command. This option only calls status for sysvinit jobs
+service --status-all
+# upstart jobs can be queried in a similar manner with initctl list
+initctl list
+# on older Ubuntu like 14.04, you probably also have update-rc.d, but that doesn't have a 'list' command
+# You could 'manually' search all the init scripts for the right runlevel
+grep -i 'runlevel' /etc/init/*| awk '!/#/ && /start on/ && /2/ {gsub("/"," "); print $0  }' | cut -d ' ' -f4-
+# or
+grep -i 'runlevel' /etc/init/* | awk '/start on/ && /2/ {gsub("/"," "); gsub(":", " ");gsub(".conf"," "); print $3  }'
+# the RedHat way (using chkconfig)
 chkconfig --list
 # for newer systemd controlled systems
 systemctl list-units
-</source>
+</syntaxhighlight>
 Here is an example list of the services you might find on your machine:
 # NetworkManager
@@ Line 130: / Line 140: @@
 === Enable/Disable/Start/Stop/Status a service ===
-<source lang="bash">
+<syntaxhighlight lang="bash">
 # for older systems using System V style init
 chkconfig apache on|off|start|stop|status
 # for newer systemd controlled systems
 systemctl enable|disable|start|stop|status <servicename>.service
-</source>
+</syntaxhighlight>
+== SystemD targets ==
+To switch to single-user mode, what used to be called '''runlevel 1''', on a modern Linux running SystemD, you would now use the command:
+<code>sudo systemctl isolate rescue.target</code>
+courtesy of https://askubuntu.com/questions/788323/how-do-i-change-the-runlevel-on-systemd
 == More ==