Difference between revisions of "Daemons"
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| − | A [[Wikipedia:Daemon (computing)|daemon]] is a program that runs | + | A [[Wikipedia:Daemon (computing)|daemon]] is a program that runs as a "background" process (without a terminal or user interface), commonly waiting for events to occur and offering services. A good example is a web server that waits for a request to deliver a page, or a ssh server waiting for someone trying to log in. While these are full featured applications, there are daemons whose work is not that visible. Daemons are for tasks like writing messages into a log file (e.g. {{ic|syslog}}, {{ic|metalog}}) or keeping your system time accurate (e.g. [[Network Time Protocol daemon|{{ic|ntpd}}]]). For more information see {{ic|man 7 daemon}}. |
{{Note|The word daemon is sometimes used for a class of programs that are started at boot but have no process which remains in memory. They are called daemons simply because they utilize the same startup/shutdown framework (e.g. systemd service files of Type oneshot) used to start traditional daemons. For example, the service files for {{ic|alsa-store}} and {{ic|alsa-restore}} provide persistent configuration support but do not start additional background processes to service requests or respond to events. | {{Note|The word daemon is sometimes used for a class of programs that are started at boot but have no process which remains in memory. They are called daemons simply because they utilize the same startup/shutdown framework (e.g. systemd service files of Type oneshot) used to start traditional daemons. For example, the service files for {{ic|alsa-store}} and {{ic|alsa-restore}} provide persistent configuration support but do not start additional background processes to service requests or respond to events. | ||
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==Managing daemons== | ==Managing daemons== | ||
| − | In Arch Linux, daemons are | + | In Arch Linux, daemons are managed by [[systemd]]. The [[systemd#Basic systemctl usage|systemctl]] command is the user interface used to manage them. It reads ''<service>''.service files that contain information about how and when to start the associated daemon. Service files are stored in {{ic|/{etc,usr/lib,run}/systemd/system}}. See [[systemd#Using units]] for complete information about using systemctl to manage daemons. |
===Starting on boot=== | ===Starting on boot=== | ||
| − | + | To add or remove services to be started at boot-time, use {{ic|systemctl enable<nowiki>|</nowiki>disable ''<service_name>''}} | |
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===Starting manually=== | ===Starting manually=== | ||
| − | To start or stop services at runtime, use {{ic|systemctl start<nowiki>|</nowiki>stop ''< | + | To start or stop services at runtime, use {{ic|systemctl start<nowiki>|</nowiki>stop ''<service_name>''}}. |
===Restarting=== | ===Restarting=== | ||
| − | To restart services, use {{ic|systemctl restart ''<service>''}}. | + | To restart services, use {{ic|systemctl restart ''<service_name>''}}. |
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| + | ===Status reporting=== | ||
| + | To report the current status of a service, use {{ic|systemctl status ''<service_name>''}}. | ||
==List of daemons== | ==List of daemons== | ||
Revision as of 13:22, 8 February 2013
zh-CN:Daemon
A daemon is a program that runs as a "background" process (without a terminal or user interface), commonly waiting for events to occur and offering services. A good example is a web server that waits for a request to deliver a page, or a ssh server waiting for someone trying to log in. While these are full featured applications, there are daemons whose work is not that visible. Daemons are for tasks like writing messages into a log file (e.g. syslog, metalog) or keeping your system time accurate (e.g. ntpd). For more information see man 7 daemon.
alsa-store and alsa-restore provide persistent configuration support but do not start additional background processes to service requests or respond to events.
From the user's perspective the distinction is typically not significant unless the user tries to look for the "daemon" in a process list.
Contents
Managing daemons
In Arch Linux, daemons are managed by systemd. The systemctl command is the user interface used to manage them. It reads <service>.service files that contain information about how and when to start the associated daemon. Service files are stored in /{etc,usr/lib,run}/systemd/system. See systemd#Using units for complete information about using systemctl to manage daemons.
Starting on boot
To add or remove services to be started at boot-time, use systemctl enable|disable <service_name>
Starting manually
To start or stop services at runtime, use systemctl start|stop <service_name>.
Restarting
To restart services, use systemctl restart <service_name>.
Status reporting
To report the current status of a service, use systemctl status <service_name>.
List of daemons
See Daemons List for a list of daemons with the name of the service and legacy rc.d script.
See also
- systemd
- Examples for writing Systemd/Services