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| A [[WikiPedia:Daemon_(computing)|daemon]], or service, is a background process usually started during the initial boot sequence by [[init]]. Daemons typically run independent of users, waiting for system events to occur and providing services in response. Some common daemons include: | <<TableOfContents>> == What is a daemon? == A [[WikiPedia:Daemon_(computing)|daemon]], or system service, is a background process usually started during the initial boot sequence by [[init]]. Daemons typically run independent of users, waiting for system events to occur and providing services in response. Some common daemons include: |
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| ## If your page gets really long, uncomment this Table of Contents ## <<TableOfContents(2)>> |
== Managing daemons in Debian == Debian makes use of [[WikiPedia:Init#SysV-style|System V]]-style init scripts for daemon management. This allows daemons to operate conditionally, based on the current RunLevel of the computer. For example, a daemon can be configured to run only when the computer is in single-user mode (runlevel 1) or, more commonly, when in multi-user mode (runlevels 2-5). For more information, see [[init]] and [[RunLevel]]. |
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| == Managing daemons in Debian == Debian makes use of [[WikiPedia:Init#SysV-style|System V]]-style init scripts for daemon management. This allows daemons to operate conditionally, based on the current RunLevel of the computer. For example, a daemon can be configured to run only when the computer is in single-user mode (runlevel 1) or, more commonly, when in multi-user mode (runlevels 2-5). For more information, see RunLevel. |
=== A brief introduction to daemon scripts === Under Debian, daemon init scripts are stored in {{{/etc/init.d/}}} |
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| == Daemon configuration == | When a daemon is enabled or disabled, symbolic links targeting the respective init script are created or removed under the various {{{/etc/rc*.d/}}} directories, corresponding to the RunLevel(s) in which the daemon is to run. To view a list of currently available services: {{{ $ ls /etc/init.d }}} === Common service tasks === Most system services accept a common set of options, which can be passed directly to the daemon script at the command line, for example: {{{ # /etc/init.d/ssh restart Restarting OpenBSD Secure Shell server: sshd. }}} A brief description of the most common options follows: * '''start''': start a service * '''stop''': stop a service * '''restart''': restart a service without reloading its job config file * '''reload''': send a SIGHUP signal to running process * '''status''': return the status of a service Starting and stopping daemons in this manner is temporary and will not survive a reboot. Refer to the next section to enable/disable daemons on a permanent basis. === Enable/disable daemons === |
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| === Start, stop and reload daemons === The easiest way to manually (and temporarily) start, stop or reload a daemon is to run the following in a terminal as root: |
Several tools exist to manage system services, including DebianPkg:rcconf and DebianPkg:sys-v-conf. The default tool however is '''update-rc.d''' and that is what the following examples use. ==== Enabling services ==== To (re)enable a service, using the default settings, run the following: |
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| # /etc/init.d/daemonname [stop|start|restart] | # update-rc.d <servicename> defaults |
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| Controlling daemons in this manner is temporary and will not survive a reboot. Refer to the next section to manage daemons on a more permanent basis. | |
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| === Enable/disable daemons === | ==== Disabling services ==== To disable a service, run the following in a terminal as root: {{{ # update-rc.d -f <servicename> remove }}} |
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| For more detail on what these commands do, refer to the [[DebianMan:8/update-rc.d|update-rc.d manpage]]. |
Translation(s): English
Contents
What is a daemon?
A daemon, or system service, is a background process usually started during the initial boot sequence by ?init. Daemons typically run independent of users, waiting for system events to occur and providing services in response. Some common daemons include:
sshd - listens for and manages incoming ?SSH connections
acpid - listens for power management events and executes scripts based on them
apache - provides a local HTTP web server
Managing daemons in Debian
Debian makes use of System V-style init scripts for daemon management. This allows daemons to operate conditionally, based on the current RunLevel of the computer. For example, a daemon can be configured to run only when the computer is in single-user mode (runlevel 1) or, more commonly, when in multi-user mode (runlevels 2-5). For more information, see ?init and RunLevel.
A brief introduction to daemon scripts
Under Debian, daemon init scripts are stored in /etc/init.d/
When a daemon is enabled or disabled, symbolic links targeting the respective init script are created or removed under the various /etc/rc*.d/ directories, corresponding to the RunLevel(s) in which the daemon is to run.
To view a list of currently available services:
$ ls /etc/init.d
Common service tasks
Most system services accept a common set of options, which can be passed directly to the daemon script at the command line, for example:
# /etc/init.d/ssh restart Restarting OpenBSD Secure Shell server: sshd.
A brief description of the most common options follows:
start: start a service
stop: stop a service
restart: restart a service without reloading its job config file
reload: send a SIGHUP signal to running process
status: return the status of a service
Starting and stopping daemons in this manner is temporary and will not survive a reboot. Refer to the next section to enable/disable daemons on a permanent basis.
Enable/disable daemons
Note: Many daemons provide essential services to a working Debian installation; others can pose unnecessary security risks when enabled carelessly. Caution should be used whenever managing daemons. When in doubt, refer to the documentation of the daemon itself.
Several tools exist to manage system services, including rcconf and sys-v-conf. The default tool however is update-rc.d and that is what the following examples use.
Enabling services
To (re)enable a service, using the default settings, run the following:
# update-rc.d <servicename> defaults
Disabling services
To disable a service, run the following in a terminal as root:
# update-rc.d -f <servicename> remove
For more detail on what these commands do, refer to the update-rc.d manpage.
See also