File:  [NetBSD Developer Wiki] / wikisrc / guide / rc.mdwn
Revision 1.2: download - view: text, annotated - select for diffs
Fri Mar 1 16:49:18 2013 UTC (8 years, 7 months ago) by jdf
Branches: MAIN
CVS tags: HEAD
Add missing hash signs.

    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`.
   32:  * `/etc/rc` sorts the scripts in `/etc/rc.d` using 
   33:    [rcorder(8)]( 
   34:    and then runs them in that order. See below and the manpage for details of
   35:    how the order of rc.d scripts is determined.
   36:  * `/etc/rc.subr` contains common functions used by `/etc/rc` and various rc.d 
   37:    scripts.
   38:  * When shutting down the system with 
   39:    [shutdown(8)](, 
   40:    `/etc/rc.shutdown` is run, which runs the scripts in `/etc/rc.d` in
   41:    reverse order (as defined by 
   42:    [rcorder(8)](  
   43:    *Note*: If you shut down the system using the 
   44:    [halt(8)]( 
   45:    command, these scripts will not be run.
   47: There are some special scripts outside the `rc.d` directory, which are also
   48: run:
   50:  * `/etc/rc.lkm` loads or unloads Loadable Kernel Modules (LKMs). See 
   51:    [modload(8)]( 
   52:    and `/etc/rc.d/lkm[123]`.
   53:  * `/etc/rc.local` is almost the last script called at boot up. This script can 
   54:    be edited by the administrator to start local daemons that don't fit the
   55:    rc.d model, or do maintenance that should be done only once at startup.
   57: rc.d scripts are controlled by a central configuration file, `/etc/rc.conf`, 
   58: which loads its default settings from `/etc/defaults/rc.conf`. If you want to 
   59: change a default setting, do not edit `/etc/defaults/rc.conf`; instead, override 
   60: the setting in `/etc/rc.conf`.
   62: It is a good idea to read the 
   63: [rc.conf(5)]( 
   64: man page to learn about the services that are by default available to you.
   66: The following example shows how to enable the SSH daemon, which is disabled by 
   67: default:
   69:     # cd /etc; grep ssh defaults/rc.conf
   70:     sshd=NO                 sshd_flags=""
   71:     # echo "sshd=YES" >> rc.conf
   73: Now [sshd(8)]( 
   74: will be started automatically at system startup. The next section describes how 
   75: to start and stop services at any time.
   77: Last but not least, files can be created in the `/etc/rc.conf.d/` directory to 
   78: override the behavior of a given rc.d script without editing the script itself.
   80: ## The rc.d scripts
   82: The actual scripts that control services are in `/etc/rc.d`. These scripts are 
   83: automatically run at boot time, but they can be called manually if necessary. 
   84: The following example shows how to start the SSH daemon that we enabled in the 
   85: previous section:
   87:     # /etc/rc.d/sshd start
   88:     Starting sshd.
   90: Later, if you wish to stop the SSH daemon, run the following command:
   92:     # /etc/rc.d/sshd stop
   93:     Stopping sshd.
   94:     Waiting for PIDS: 123.
   96: The rc.d scripts take one of the following arguments:
   98:  * `start`
   99:  * `stop`
  100:  * `restart`
  101:  * `status`
  103: Some scripts may support other arguments (e.g., `reload`), but every script will 
  104: support at least the above commands.
  106: As an example, after adding a new record to a 
  107: [named(8)]( 
  108: database, the daemon can be told to reload its configuration files with the 
  109: following command:
  111:     # /etc/rc.d/named reload
  112:     Reloading named config files.
  114: Note that all of the commands discussed above will only take action if the 
  115: particular service is enabled in `/etc/rc.conf`. It is possible to bypass this 
  116: requirement by prepending `one` to the command, as in:
  118:     # /etc/rc.d/httpd start
  119:     $httpd is not enabled - see rc.conf(5).
  120:     Use the following if you wish to perform the operation:
  121:       /etc/rc.d/httpd onestart
  122:     # /etc/rc.d/httpd onestart
  123:     Starting httpd.
  125: The above command will allow you to start the 
  126: [httpd(8)]( 
  127: service one time. To stop a service that has been started in this manner, pass 
  128: `onestop` to the script.
  130: ## Order/dependencies of start determined by rcorder
  132: The startup system of every Unix system determines, in one way or another, the 
  133: order in which services are started. On some Unix systems this is done by 
  134: numbering the files and/or putting them in separate run level directories. 
  135: Solaris relies on wildcards like `/etc/rc[23].d/S*` being sorted numerically 
  136: when expanded. Some simply put all the commands that should be started into a 
  137: single monolithic script (this is the traditional BSD method, and is what NetBSD 
  138: did before the rc.d system). On modern NetBSD this is done by the rc.d scripts 
  139: and their contents. Please note that NetBSD does not have multiple runlevels as 
  140: found in SysV-style systems like Solaris and Linux.
  142: At the beginning of each rc.d script there is a series of commented out lines 
  143: that have one of the following items in them:
  145:  * `REQUIRE`
  146:  * `PROVIDE`
  147:  * `BEFORE`
  148:  * `KEYWORD`
  150: These describe the dependencies of that particular script and allow rcorder to 
  151: easily work either `up` or `down` as the situation requires. As an example, here 
  152: is the ordering information contained in `/etc/rc.d/nfsd`:
  154:     ...
  155:     # PROVIDE: nfsd
  156:     # REQUIRE: rpcbind mountd
  157:     ...
  159: Here we can see that this script provides the `nfsd` service and that it 
  160: requires `rpcbind` and `mountd` to be running first. The 
  161: [rcorder(8)]( 
  162: utility is used at system startup time to read through all the rc.d scripts and 
  163: determine the order in which they should be run.
  165: ## rc.d scripts of additional services
  167: Packages you install additionally won't be listed in the rc.conf(5) manpage.
  168: Packages installing services which can be started with an rc.d script tell you
  169: so after they are installed, along with the variable that is used for starting
  170: them (usually, it has the same name as the service itself).
  172: Then, you usually have to copy them from `/usr/pkg/share/examples/rc.d` to
  173: `/etc/rc.d` for `rc` to automatically find them, or add the line
  175:     rc_directories="/etc/rc.d /usr/pkg/share/examples/rc.d"
  177: to your `/etc/rc.conf`.
  179: If you forgot the name of the service variable, you can have a look at the rc.d
  180: script itself. The variable `rcvar` (usually set to `$name`) will tell you.
  181: E.g., to find the name of variable to start fscd, run
  183:     $ grep ^rcvar /etc/rc.d/fscd
  184: 	rcvar=${name}
  185: 	$ grep ^name /etc/rc.d/fscd   # Aaaw, no direct rcvar.
  186: 	name="fscd"
  188: Thus, you need in your `/etc/rc.conf` the entry:
  190:     fscd="YES"
  192: ## Additional Reading
  194: Luke Mewburn, one of the principal designers of the rc.d system, gave a 
  195: presentation on the system at USENIX 2001. It is available in 
  196: [PDF]( format.

CVSweb for NetBSD wikisrc <> software: FreeBSD-CVSweb