A daemon is a program that runs in the background, waiting for events to occur and offering services. A good example is a webserver 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. A daemon which writes messages into a log file (e.g. syslog, metalog), a daemon which lowers your CPU frequency if the system has nothing to do.
Starting on Boot
A default install of Arch Linux will leave you with very few services (or daemons) enabled during boot. You can add or remove services by editing the the daemon array line in your rc.conf file. It will initially look something like this:
DAEMONS=(syslog-ng network netfs crond)
They will start in the order you have them listed. You can disable one and keep it in the array by prefixing it with an exclamation mark (!). You can also have them start in the background by adding an at (@) symbol in front of it.
Manual Starting and Stopping
You can see what service start up scripts you have by looking in your /etc/rc.d/ directory. You can also manually start, stop, and restart them by issuing
They may also have other commands, check with the documentation.
Note that some services will start other services. For example, HAL will automatically start D-Bus and Acpid. But also please remember, as has been mentioned elsewhere, that HAL sometimes fails to automatically start D-Bus, and without the user being aware of that fact. It is considered good practice to add D-Bus explicitly before HAL, and to not "background" it. This will let the user know during bootup if it fails to start, before other services dependent on D-Bus break.
Keep in mind, as you install new services, that you will have to manually add them to rc.conf.
Starting Daemons in Background
This is helpful for starting a service and letting the next service start before the previous one has finished. Which services to start background depends on your needs. Do not background anything you need immediately. Here is an example:
DAEMONS=(syslog-ng gensplash network netfs dbus hal @avahi-daemon @samba @crond @alsa @openntpd @cups @mpd)
Starting openntpd in the background could lead to synchronization errors between the actual time and the time stored on your computer. If you recognize an increasing time difference between your desktop clock and the actual time, try to start the openntpd daemon normally and not in the background.
ArchLinux Daemon Manager GUI
List of Daemons
(Here is a list of daemons, although it might not be complete. Please feel free to add any missing daemons here, in alphabetical order.)
|alsa||Enables sound with the Advanced Linux Sound Architecture.|
|crond||Daemon to schedule and time events.|
|cups||Common UNIX Printing System daemon.|
|dbus||Message bus system for software communication.|
|hal||Hardware Abstraction Layer|
|mysqld||Daemon to connect to MySQL databases|
|netfs||Creates network file system.|
|rsyslogd||The latest version of a system logger.|
|stbd||This daemon was previously necessary for gnome-system-tools. However, as of gnome-tools 2.28, it is no longer needed.|
|syslogd||This was the older and basic system logger.|
|syslog-ng||System logger next generation.|