File:  [NetBSD Developer Wiki] / wikisrc / guide / rc.mdwn
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Tue Mar 5 23:33:53 2013 UTC (8 years, 7 months ago) by jdf
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Cosmetics (mainly removing trailing whitespaces).

    1: # The rc.d System
    3: NetBSD uses individual scripts for controlling system and service startup,
    4: similar to System V, but without runlevels.
    5: Nowadays, most Linux distributions switched to systemd, which is a different
    6: approach: It does not use scripts anymore, but tries to have everything binary.
    7: It also serves for several other purposes, while NetBSD's rc.d system just
    8: serves for starting up services at system startup or by user intervention.
   10: This chapter is an overview of NetBSD's rc.d system and its configuration.
   12: ## Basics
   14: The system startup files reside in the `/etc` directory. They are:
   16:  * `/etc/rc`
   17:  * `/etc/rc.conf`
   18:  * `/etc/rc.d/*`
   19:  * `/etc/rc.lkm`
   20:  * `/etc/rc.local`
   21:  * `/etc/rc.shutdown`
   22:  * `/etc/rc.subr`
   23:  * `/etc/defaults/*`
   24:  * `/etc/rc.conf.d/*`
   26: First, a look at controlling and supporting scripts (also documented in
   27: [rc(8)](
   29:  * After the kernel has initialized all devices at startup, it starts
   30:    [init(8)](,
   31:    which in turn runs `/etc/rc`.
   33:  * `/etc/rc` sorts the scripts in `/etc/rc.d` using
   34:    [rcorder(8)](
   35:    and then runs them in that order. See below and the manpage for details of
   36:    how the order of rc.d scripts is determined.
   38:  * `/etc/rc.subr` contains common functions used by `/etc/rc` and various rc.d
   39:    scripts.
   41:  * When shutting down the system with
   42:    [shutdown(8)](,
   43:    `/etc/rc.shutdown` is run, which runs the scripts in `/etc/rc.d` in
   44:    reverse order (as defined by
   45:    [rcorder(8)](
   47:    *Note*: If you shut down the system using the
   48:    [halt(8)](
   49:    command, these scripts will not be run.
   51: There are some special scripts outside the `rc.d` directory, which are also
   52: run:
   54:  * `/etc/rc.lkm` loads or unloads Loadable Kernel Modules (LKMs). See
   55:    [modload(8)](
   56:    and `/etc/rc.d/lkm[123]`.
   58:  * `/etc/rc.local` is almost the last script called at boot up. This script can
   59:    be edited by the administrator to start local daemons that don't fit the
   60:    rc.d model, or do maintenance that should be done only once at startup.
   62: rc.d scripts are controlled by a central configuration file, `/etc/rc.conf`,
   63: which loads its default settings from `/etc/defaults/rc.conf`. If you want to
   64: change a default setting, do not edit `/etc/defaults/rc.conf`; instead, override
   65: the setting in `/etc/rc.conf`.
   67: It is a good idea to read the
   68: [rc.conf(5)](
   69: man page to learn about the services that are by default available to you.
   71: The following example shows how to enable the SSH daemon, which is disabled by
   72: default:
   74:     # cd /etc; grep ssh defaults/rc.conf
   75:     sshd=NO                 sshd_flags=""
   76:     # echo "sshd=YES" >> rc.conf
   78: Now [sshd(8)](
   79: will be started automatically at system startup. The next section describes how
   80: to start and stop services at any time.
   82: Last but not least, files can be created in the `/etc/rc.conf.d/` directory to
   83: override the behavior of a given rc.d script without editing the script itself.
   85: ## The rc.d scripts
   87: The actual scripts that control services are in `/etc/rc.d`. These scripts are
   88: automatically run at boot time, but they can be called manually if necessary.
   89: The following example shows how to start the SSH daemon that we enabled in the
   90: previous section:
   92:     # /etc/rc.d/sshd start
   93:     Starting sshd.
   95: Later, if you wish to stop the SSH daemon, run the following command:
   97:     # /etc/rc.d/sshd stop
   98:     Stopping sshd.
   99:     Waiting for PIDS: 123.
  101: The rc.d scripts take one of the following arguments:
  103:  * `start`
  104:  * `stop`
  105:  * `restart`
  106:  * `status`
  108: Some scripts may support other arguments (e.g., `reload`), but every script will
  109: support at least the above commands.
  111: As an example, after adding a new record to a
  112: [named(8)](
  113: database, the daemon can be told to reload its configuration files with the
  114: following command:
  116:     # /etc/rc.d/named reload
  117:     Reloading named config files.
  119: Note that all of the commands discussed above will only take action if the
  120: particular service is enabled in `/etc/rc.conf`. It is possible to bypass this
  121: requirement by prepending `one` to the command, as in:
  123:     # /etc/rc.d/httpd start
  124:     $httpd is not enabled - see rc.conf(5).
  125:     Use the following if you wish to perform the operation:
  126:       /etc/rc.d/httpd onestart
  127:     # /etc/rc.d/httpd onestart
  128:     Starting httpd.
  130: The above command will allow you to start the
  131: [httpd(8)](
  132: service one time. To stop a service that has been started in this manner, pass
  133: `onestop` to the script.
  135: ## Order/dependencies of start determined by rcorder
  137: The startup system of every Unix system determines, in one way or another, the
  138: order in which services are started. On some Unix systems this is done by
  139: numbering the files and/or putting them in separate run level directories.
  140: Solaris relies on wildcards like `/etc/rc[23].d/S*` being sorted numerically
  141: when expanded. Some simply put all the commands that should be started into a
  142: single monolithic script (this is the traditional BSD method, and is what NetBSD
  143: did before the rc.d system). On modern NetBSD this is done by the rc.d scripts
  144: and their contents. Please note that NetBSD does not have multiple runlevels as
  145: found in SysV-style systems like Solaris and Linux.
  147: At the beginning of each rc.d script there is a series of commented out lines
  148: that have one of the following items in them:
  150:  * `REQUIRE`
  151:  * `PROVIDE`
  152:  * `BEFORE`
  153:  * `KEYWORD`
  155: These describe the dependencies of that particular script and allow rcorder to
  156: easily work either `up` or `down` as the situation requires. As an example, here
  157: is the ordering information contained in `/etc/rc.d/nfsd`:
  159:     ...
  160:     # PROVIDE: nfsd
  161:     # REQUIRE: rpcbind mountd
  162:     ...
  164: Here we can see that this script provides the `nfsd` service and that it
  165: requires `rpcbind` and `mountd` to be running first. The
  166: [rcorder(8)](
  167: utility is used at system startup time to read through all the rc.d scripts and
  168: determine the order in which they should be run.
  170: ## rc.d scripts of additional services
  172: Packages you install additionally won't be listed in the rc.conf(5) manpage.
  173: Packages installing services which can be started with an rc.d script tell you
  174: so after they are installed, along with the variable that is used for starting
  175: them (usually, it has the same name as the service itself).
  177: Then, you usually have to copy them from `/usr/pkg/share/examples/rc.d` to
  178: `/etc/rc.d` for `rc` to automatically find them, or add the line
  180:     rc_directories="/etc/rc.d /usr/pkg/share/examples/rc.d"
  182: to your `/etc/rc.conf`.
  184: If you forgot the name of the service variable, you can have a look at the rc.d
  185: script itself. The variable `rcvar` (usually set to `$name`) will tell you.
  186: E.g., to find the name of variable to start fscd, run
  188:     $ grep ^rcvar /etc/rc.d/fscd
  189: 	rcvar=${name}
  190: 	$ grep ^name /etc/rc.d/fscd   # Aaaw, no direct rcvar.
  191: 	name="fscd"
  193: Thus, you need in your `/etc/rc.conf` the entry:
  195:     fscd="YES"
  197: ## Additional Reading
  199: Luke Mewburn, one of the principal designers of the rc.d system, gave a
  200: presentation on the system at USENIX 2001. It is available in
  201: [PDF]( format.

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