A Linux User Reference

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  • Linux Standard Base specification (LSB)

    It incorporates, among other things, a means to standardise the implementation of 'init' scripts.

    When installing and removing packaged 'init scripts' LSB compliant package's post-install and post-deinstall/remove scripts call 'install_initd' and 'remove_initd'. Both scripts are in /usr/lib/lsb/.

    Each initd script to be installed/removed by this method must conform to the LSB standard and incorporate a comment header containing information on how it wants to be installed.

  • LSB initd install and remove scripts
    /usr/lib/lsb/install_initd, remove_initd

    Install an LSB compliant init script

    install_initd [/path/to/init.d/script]

    It creates the Start/Stop (S../K..) symlinks in the appropriate 'rc...d' directories based on the information in the script header.

    If an init script specifies the following in its comment header file

    # Default-Start: 3 4 5
    # Default-Stop: 0 1 2 6

    then 'install_initd' should create

    • Start symbolic links with names starting with 'S' in /etc/rc3.d, /etc/rc4.d, /etc/rc5.d
    • Stop symbolic links with names starting with 'K' in /etc/rc0.d, /etc/rc1.d, /etc/rc2.d, /etc/rc6.d

    Remove an LSB compliant init script

    remove_initd [/path/to/init.d/script]

    Remove, deinstall an LSB compliant 'init script' by removing the script's symbolic links in the 'rc*.d' directories.

  • LSB init script Comment header

    At least the following info should be provider in any compliant 'init' script as a comment header

    # Provides:        boot_facility_1 [ boot_facility_2 ...]
    # Required-Start:  boot_facility_1 [ boot_facility_2 ...]
    # Required-Stop:   boot_facility_1 [ boot_facility_2 ...]
    # Should-Start:    boot_facility_1 [ boot_facility_2 ...]
    # Should-Stop:     boot_facility_1 [ boot_facility_2 ...]
    # Default-Start:   run_level_1 [ run_level_2 ...]
    # Default-Stop:    run_level_1 [ run_level_2 ...]
    # Description:     multiline_description
    Parameter: Value Description
    Provides: boot_facility_1 [boot_facility_2...] Boot facilities provided by this init script. When an init script is run with a start argument, the boot facility(s) specified shall be deemed present and hence init scripts which require those boot facilities should be started later. When an init script is run with a stop argument, the boot facility(s) specified are deemed no longer present.
    Required-Start: boot_facility_1 [boot_facility_2...] Facilities which must be available during startup of this service. The init-script system should insure init scripts which provide the Required-Start facilities are started before starting this script.
    Required-Stop: boot_facility_1 [boot_facility_2...] Facilities which must be available during the shutdown of this service. The init-script system should avoid stopping init scripts which provide the Required-Stop facilities until this script is stopped.
    Should-Start: boot_facility_1 [boot_facility_2...] Facilities which, if present, should be available during startup of this service. This allows for weak dependencies which do not cause the service to fail if a facility is not available. The service may provide reduced functionality in this situation. Conforming applications should not rely on the existence of this feature.
    Should-Stop: boot_facility_1 [boot_facility_2...] Facilities which should be available during shutdown of this service.
    Default-Start: run_level_1 [run_level_2...] Which run levels should by default run the init script with a start (stop) argument to start (stop) the services controlled by the init script e.g. if a service should run in runlevels 3, 4, and 5 only, specify Default-Start: 3 4 5 and Default-Stop: 0 1 2 6.
    Default-Stop: run_level_1 [run_level_2...] See above description
    Short-Description: short_description Provide a brief description of the actions of the init script. Limited to a single line of text.
    Description: multiline_description Provide a more complete description of the actions of the init script. May span multiple lines. In a multiline description, each continuation line shall begin with a # followed by tab character or a # followed by at least two space characters. The multiline description is terminated by the first line that does not match this criteria.
  • LSB initd script management tool

    Manages installed system init scripts by reading the comment header of the script.

    Command usage

    insserv [options] [/path/to/init.d/]script ...
    insserv [-v] [/path/to/init.d/]script[,start=[,]] ...
    Common options:
     -v | --verbose           Write out what is currently going on.
     -n | --dryrun            Do not update symlinks.
     -r | --remove            Remove the space separated list of scripts from all runlevels.
     -d | --default           Use default runlevels defined in the scripts. May restore an 
                              edited runlevel link scheme.
     -f | --force             Ignore if a required service is missed.
    Valid runlevels:
     0, 1, 2, 3, 4, 5, 6,
     S,                       S is used during boot into single user mode.
     B                        B is used during boot before any other runlevel.
  • Sample insserv configuration file

    'insserv' scans for System Facilities in it's configuration file and each file in the directory /etc/insserv.conf.d/

    Sample, default innserv.conf

    # All local filesystems are mounted (done during boot phase)
    $local_fs  boot               // Each line which begins with $ and a following name defines a system
                                  // facility according to the LSB. All names followed by such a system
                                  // facility will declare the required dependencies of the facility.
    # Low level networking
    $network   network route
    # Named is operational
    $named     named
    # All remote filesystems are mounted 
    # (in some cases /usr may be remote).
    $remote_fs $local_fs nfs
    # System logger is operational
    $syslog    syslog
    # All network daemons are running
    $netdaemons     portmap inetd
    # Services which need to be interactive

    Names starting with a + sign are marked as optional. If the service with the name is available it will be used, if not available it is ignored silently.

    Words enclosed in <> are keywords. Currently is the only known keyword for marking a service as an interactive one, e.g. a service which requires a passphrase or password input during boot or runlevel change.

  • LSB compliant command

    Runs the specified program as a daemon.

    Command usage

    start_daemon [-f] [-n nicelevel] 
                 [-p pidfile] pathname [args...]
  • LSB compliant command

    Send [signal] to all processes that use the specified executable. Default=SIGTERM. If SIGTERM is used and does not terminate a process, SIGKILL is sent after a few seconds (default is 5 seconds, see option '-t').

    Command usage

    killproc [options] [-p pidfile] 
             pathname [signal]

    Send SIGTERM to the running sendmail process

    # killproc -TERM /usr/sbin/sendmail

    If a pid file '' exists in '/var/run/' then the pid from this file is used (after verification) to terminate the Sendmail process. Other running processes are ignored.

    Send SIGTERM to the pid found in /var/myrun/

    # killproc -p /var/myrun/ -TERM /usr/sbin/lpd

    Sends signal if and only if this pid belongs to '/usr/sbin/lpd'. If the named '/var/myrun/' does not exist, 'killproc' assumes that the daemon of '/usr/sbin/lpd' is not running.

  • LSB compliant command

    Return one or more process identifiers for a particular daemon.

    Command usage

    pidofproc [-p pidfile] pathname
  • LSB compliant command

    Starts a process belonging to a particular executable. It checks for processes belonging to the specified executable and starts any. If no processes are found it does not use the pid to search for a process but the full path of the corresponding program.

    Command usage

    startproc [options] 
              /path/to/executable [executable args]

    Start /usr/sbin/sendmail if no sendmail process is found

    # startproc /usr/sbin/sendmail

    If '/var/run/' exists it is used to search for a process with an executable that matches '/usr/sbin/sendmail'.

    Start lpd if no process with the pid is found in '/var/myrun/' and there is no existing process that uses the specified binary

    # startproc -p /var/myrun/ /usr/sbin/lpd
  • LSB compliant command

    Checks for a process by full path name.

    Command usage

    checkproc [-options] [-p pid_file] 

    Return all pids of running sendmail processes

    # checkproc /usr/sbin/sendmail

    Return the command line or the basename of the process pid found in /var/run/

    # checkproc -p /var/myrun/ /usr/sbin/lpd
  • LSB compliant command

    Start runlevel scripts in parallel. Scans the boot and runlevel directories in /etc/init.d/ then executes the appropriate scripts in parallel.

    Command usage

    startpar [options] [-a arg] prg1 prg2 ...
    startpar [options] -M [boot|start|stop]
     -p                Sets degree of parallelism on one CPU, default is full parallelism.
     -a arg            Provides an argument to all of the scripts
     -t                Buffer timeout
     -T                Timeout works more globally
     -M                Option switches startpar into a make(1) like behaviour
                       three different arguments: 
                       boot | start | stop
                       for reading .depend.boot, .depend.start or .depend.stop in /etc/init.d/
  • LSB compliant, SysV style init script management command

    List, add, delete, manage system startup services by manipulating the runlevel links at boot time. It can be thought of as a frontend to 'insserv'.

    Command usage

    chkconfig [options]
     --list [name]                    List status of all or name service if given.
     --add                            Add service/name rc script file to /etc/init.d
     --del                            Disable/enable a service during boot process
     [--level ]      

    Display the runlevels system services run at

    # chkconfig --list|more
    ConsoleKit      0:off   1:off   2:off   3:on    4:on    5:on    6:off
    NetworkManager  0:off   1:off   2:off   3:off   4:off   5:off   6:off
    NetworkManagerDispatcher        0:off   1:off   2:off   3:off   4:off   5:off   6:off
    Anacron         0:off   1:off   2:on    3:on    4:on    5:on    6:off
  • Debian's install and remove SysV style init script links

    This is debians alternative to of 'chkconfig', 'insserv' ...

    Command usage

    update-rc.d [options]
     [-n] [-f] service remove
     [-n] [-f] service defaults [nn | nn-start nn-stop]
     [-n] [-f] service [ start | stop nn runlevel runlevel ...  ] [ start | stop .....] 

    Add links for K99foo from /etc/rc0,1,6.d and S99foo from /etc/rc.2,3,4,5.d -> ../init.d/foo

    # update-rc.d foo defaults 99

    Remove all K99foo and S99foo links from /etc/rc0-6.d -> /etc/init.d/foo

    # update-rc.d -f foo remove

    Add stop links for runlevels 0,1,6 and start links for 2,3,4,5

    # update-rc.d foo stop 99 0 1 6 . start 99 2 3 4 5 .