xenial (1) daemon.1.gz

Provided by: daemon_0.6.4-1_amd64 bug

NAME

       daemon - turns other processes into daemons

SYNOPSIS

        usage: daemon [options] [--] [cmd arg...]
        options:

        -h, --help                - Print a help message then exit
        -V, --version             - Print a version message then exit
        -v, --verbose[=level]     - Set the verbosity level
        -d, --debug[=level]       - Set the debugging level

        -C, --config=path         - Specify the system configuration file
        -N, --noconfig            - Bypass the system configuration file
        -n, --name=name           - Guarantee a single named instance
        -X, --command=cmd         - Specify the client command as an option
        -P, --pidfiles=/dir       - Override standard pidfile location
        -F, --pidfile=/path       - Override standard pidfile name and location

        -u, --user=user[:[group]] - Run the client as user[:group]
        -R, --chroot=path         - Run the client with path as root
        -D, --chdir=path          - Run the client in directory path
        -m, --umask=umask         - Run the client with the given umask
        -e, --env="var=val"       - Set a client environment variable
        -i, --inherit             - Inherit environment variables
        -U, --unsafe              - Allow execution of unsafe executable
        -S, --safe                - Deny execution of unsafe executable
        -c, --core                - Allow core file generation

        -r, --respawn             - Respawn the client when it terminates
        -a, --acceptable=#        - Minimum acceptable client duration (seconds)
        -A, --attempts=#          - Respawn # times on error before delay
        -L, --delay=#             - Delay between spawn attempt bursts (seconds)
        -M, --limit=#             - Maximum number of spawn attempt bursts
            --idiot               - Idiot mode (trust root with the above)

        -f, --foreground          - Run the client in the foreground
        -p, --pty[=noecho]        - Allocate a pseudo terminal for the client

        -l, --errlog=spec         - Send daemon's error output to syslog or file
        -b, --dbglog=spec         - Send daemon's debug output to syslog or file
        -o, --output=spec         - Send client's output to syslog or file
        -O, --stdout=spec         - Send client's stdout to syslog or file
        -E, --stderr=spec         - Send client's stderr to syslog or file

            --running             - Check if a named daemon is running
            --restart             - Restart a named daemon client
            --stop                - Terminate a named daemon process

DESCRIPTION

       daemon(1) turns other processes into daemons. There are many tasks that need to be performed to correctly
       set up a daemon process. This can be tedious. daemon performs these tasks for other processes.

       The preparatory tasks that daemon performs for other processes are:

       •   First revoke any setuid or setgid privileges that daemon may have been installed with (by system
           administrators who laugh in the face of danger).

       •   Process command line options.

       •   Change the root directory if the --chroot option was supplied.

       •   Change the process uid and gid if the --user option was supplied. Only root can use this option. Note
           that the uid of daemon itself is changed, rather than just changing the uid of the client process.

       •   Read the system configuration file (/etc/daemon.conf by default, or specified by the --config option)
           unless the --noconfig option was supplied. Then read the user's configuration file (~/.daemonrc), if
           any.  Generic options are processed first, then options specific to the daemon with the given name.
           Note: The root directory and the user must be set before access to the configuration file can be
           attempted so neither --chroot nor --user options may appear in the configuration file.

       •   Disable core file generation to prevent leaking sensitive information in daemons run by root (unless
           the --core option was supplied).

       •   Become a daemon process:

           •   If daemon was not invoked by init(8) or inetd(8):

               •   Background the process to lose process group leadership.

               •   Start a new process session.

               •   Under SVR4, background the process again to lose process session leadership. This prevents
                   the process from ever gaining a controlling terminal. This only happens when SVR4 is defined
                   and NO_EXTRA_SVR4_FORK is not defined when libslack(3) is compiled. Before doing this, ignore
                   SIGHUP because when the session leader terminates, all processes in the foreground process
                   group are sent a SIGHUP signal (apparently). Note that this code may not execute (e.g. when
                   started by init(8) or inetd(8) or when either SVR4 was not defined or NO_EXTRA_SVR4_FORK was
                   defined when libslack(3) was compiled). This means that the client can't make any assumptions
                   about the SIGHUP handler.

           •   Change directory to the root directory so as not to hamper umounts.

           •   Clear the umask to enable explicit file creation modes.

           •   Close all open file descriptors. If daemon was invoked by inetd(8), stdin, stdout and stderr are
               left open since they are open to a socket.

           •   Open stdin, stdout and stderr to /dev/null in case something requires them to be open. Of course,
               this is not done if daemon was invoked by inetd(8).

           •   If the --name option was supplied, create and lock a file containing the process id of the daemon
               process. The presence of this locked file prevents two instances of a daemon with the same name
               from running at the same time. The standard location of the pidfile is /var/run for root or /tmp
               for ordinary users. If the --pidfiles option was supplied, its argument specifies the directory
               in which the pidfile will be placed.  If the --pidfile option was supplied, its argument
               specifies the name of the pidfile and the directory in which it will be placed.

       •   If the --umask option was supplied, set the umask to its argument.  Otherwise, set the umask to 022
           to prevent clients from accidentally creating group or world writable files.

       •   Set the current directory if the --chdir option was supplied.

       •   Spawn the client command and wait for it to terminate. The client command may be specified as command
           line arguments or as the argument of the --command option. If both the --command option and command
           line arguments are present, the client command is the result of appending the command line arguments
           to the argument of the --command option.

       •   If the --syslog, --outlog and/or --errlog options were supplied, the client's standard output and/or
           standard error are captured by daemon and sent to the respective syslog destinations.

       •   When the client terminates, daemon respawns it if the --respawn option was supplied. If the client
           ran for less than 300 seconds (or the value of the --acceptable option), then daemon sees this as an
           error. It will attempt to restart the client up to five times (or the value of the --attempts option)
           before waiting for 300 seconds (or the value of the --delay option). This gives the administrator the
           chance to correct whatever is preventing the client from running without overloading system
           resources. If the --limit option was supplied, daemon terminates after the specified number of spawn
           attempt bursts. The default is zero which means never give up, never surrender.

           When the client terminates and the --respawn option wasn't supplied, daemon terminates.

       •   If daemon receives a SIGTERM signal, it propagates the signal to the client and then terminates.

       •   If daemon receives a SIGUSR1 signal (from another invocation of daemon supplied with the --restart
           option), it sends a SIGTERM signal to the client. If started with the --respawn option, the client
           process will be restarted after it is killed by the SIGTERM signal.

       •   If the --foreground option was supplied, the client process is run as a foreground process and is not
           turned into a daemon. If daemon is connected to a terminal, so will the client process. If daemon is
           not connected to a terminal but the client needs to be connected to a terminal, use the --pty option.

OPTIONS

       -h, --help
           Display a help message and exit.

       -V, --version
           Display a version message and exit.

       -v[level], --verbose[=level]
           Set the message verbosity level to level (or 1 if level is not supplied). daemon does not have any
           verbose messages so this has no effect unless the --running option is supplied.

       -d[level], --debug[=level]
           Set the debug message level to level (or 1 if level is not supplied).  Level 1 traces high level
           function calls. Level 2 traces lower level function calls and shows configuration information. Level
           3 adds environment variables. Level 9 adds every return value from select(2) to the output.  Debug
           messages are sent to the destination specified by the --dbglog option (by default, the syslog(3)
           facility, daemon.debug).

       -C path, --config=path
           Specify the configuration file to use. By default, /etc/daemon.conf is the configuration file if it
           exists and is not group or world writable and does not exist in a group or world writable directory.
           The configuration file lets you predefine options that apply to all clients and to specifically named
           clients.

       -N, --noconfig
           Bypass the system configuration file, /etc/daemon.conf. Only the user's ~/.daemonrc configuration
           file will be read (if it exists).

       -n name, --name=name
           Create and lock a pid file (/var/run/name.pid), ensuring that only one daemon with the given name is
           active at the same time.

       -X cmd, --command=cmd
           Specify the client command as an option. If a command is specified along with its name in the
           configuration file, then daemons can be started merely by mentioning their name:

               daemon --name ftumpch

           Note: Specifying the client command in the configuration file means that no shell features are
           available (i.e. no meta characters).

       -P /dir, --pidfiles=/dir
           Override the standard pidfile location. The standard pidfile location is user dependent: root's
           pidfiles live in /var/run. Normal users' pidfiles live in /tmp. This option can only be used with the
           --name option. Use this option if these locations are unacceptable but make sure you don't forget
           where you put your pidfiles. This option is best used in configuration files or in shell scripts, not
           on the command line.

       -F /path, --pidfile=/path
           Override the standard pidfile name and location. The standard pidfile location is described
           immediately above. The standard pidfile name is the argument of the --name option followed by .pid.
           Use this option if the standard pidfile name and location are unacceptable but make sure you don't
           forget where you put your pidfile. This option should only be used in configuration files or in shell
           scripts, not on the command line.

       -u user[:[group]], --user=user[:[group]]
           Run the client as a different user (and group). This only works for root.  If the argument includes a
           :group specifier, daemon will assume the specified group and no other. Otherwise, daemon will assume
           all groups that the specified user is in. For backwards compatibility, "." may be used instead of ":"
           to separate the user and group but since "." may appear in user and group names, ambiguities can
           arise such as using --user=u.g with users u and u.g and group g. With such an ambiguity, daemon will
           assume the user u and group g. Use --user=u.g: instead for the other interpretation.

       -R path, --chroot=path
           Change the root directory to path before running the client. On some systems, only root can do this.
           Note that the path to the client program and to the configuration file (if any) must be relative to
           the new root path.

       -D path, --chdir=path
           Change the directory to path before running the client.

       -m umask, --umask=umask
           Change the umask to umask before running the client. umask must be a valid octal mode. The default
           umask is 022.

       -e var=val, --env=var=val
           Set an environment variable for the client process. This option can be used any number of times. If
           it is used, only the supplied environment variables are passed to the client process. Otherwise, the
           client process inherits the current set of environment variables.

       -i, --inherit
           Explicitly inherit environment variables. This is only needed when the --env option is used. When
           this option is used, the --env option adds to the inherited environment, rather than replacing it.

       -U, --unsafe
           Allow reading an unsafe configuration file and execution of an unsafe executable. A configuration
           file or executable is unsafe if it is group or world writable or is in a directory that is group or
           world writable (following symbolic links). If an executable is a script interpreted by another
           executable, then it is considered unsafe if the interpreter is unsafe. If the interpreter is
           /usr/bin/env (with an argument that is a command name to be searched for in $PATH), then that command
           must be safe. By default, daemon(1) will refuse to read an unsafe configuration file or to execute an
           unsafe executable when run by root. This option overrides that behaviour and hence should never be
           used.

       -S, --safe
           Deny reading an unsafe configuration file and execution of an unsafe executable. By default,
           daemon(1) will allow reading an unsafe configuration file and execution of an unsafe executable when
           run by ordinary users. This option overrides that behaviour.

       -c, --core
           Allow the client to create a core file. This should only be used for debugging as it could lead to
           security holes in daemons run by root.

       -r, --respawn
           Respawn the client when it terminates.

       -a #, --acceptable=#
           Specify the minimum acceptable duration in seconds of a client process. The default value is 300
           seconds. It cannot be set to less than 10 seconds except by root when used in conjunction with the
           --idiot option. This option can only be used with the --respawn option.

           less than this, it is considered to have failed.

       -A #, --attempts=#
           Number of attempts to spawn before delaying. The default value is 5. It cannot be set to more than
           100 attempts except by root when used in conjunction with the --idiot option. This option can only be
           used with the --respawn option.

       -L #, --delay=#
           Delay in seconds between each burst of spawn attempts. The default value is 300 seconds. It cannot be
           set to less than 10 seconds except by root when used in conjunction with the --idiot option. This
           option can only be used with the --respawn option.

       -M #, ---limit=#
           Limit the number of spawn attempt bursts. The default value is zero which means no limit. This option
           can only be used with the --respawn option.

       --idiot
           Turn on idiot mode in which daemon will not enforce the minimum or maximum values normally imposed on
           the --acceptable, --attempts and --delay option arguments. The --idiot option must appear before any
           of these options. Only the root user may use this option because it can turn a slight
           misconfiguration into a lot of wasted CPU effort and log messages.

       -f, --foreground
           Run the client in the foreground. The client is not turned into a daemon.

       -p[noecho], --pty[=noecho]
           Connect the client to a pseudo terminal. This option can only be used with the --foreground option.
           This is the default when the --foreground option is supplied and daemon's standard input is connected
           to a terminal. This option is only necessary when the client process must be connected to a
           controlling terminal but daemon itself has been run without a controlling terminal (e.g. from cron(8)
           or a pipeline).

           If the noecho argument is supplied with this option, the client's side of the pseudo terminal will be
           set to noecho mode. Use this only if there really is a terminal involved and input is being echoed
           twice.

       -l spec, --errlog=spec
           Send daemon's standard output and error to the syslog destination or file specified by spec. If spec
           is of the form "facility.priority", then output is sent to syslog(3). Otherwise, output is appended
           to the file whose path is given in spec. By default, output is sent to daemon.err.

       -b spec, --dbglog=spec
           Send daemon's debug output to the syslog destination or file specified by spec. If spec is of the
           form "facility.priority", then output is sent to syslog(3). Otherwise, output is appended to the file
           whose path is given in spec. By default, output is sent to daemon.debug.

       -o spec, --output=spec
           Capture the client's standard output and error and send it to the syslog destination or file
           specified by spec. If spec is of the form "facility.priority", then output is sent to syslog(3).
           Otherwise, output is appended to the file whose path is given in spec. By default, output is
           discarded unless the --foreground option is present. In this case, the client's stdout and stderr are
           propagated to daemon's stdout and stderr respectively.

       -O spec, --stdout=spec
           Capture the client's standard output and send it to the syslog destination or file specified by spec.
           If spec is of the form "facility.priority", then output is sent to syslog(3). Otherwise, stdout is
           appended to the file whose path is given in spec. By default, stdout is discarded unless the
           --foreground option is present, in which case, the client's stdout is propagated to daemon's stdout.

       -E spec, --stderr=spec
           Capture the client's standard error and send it to the syslog destination specified by spec. If spec
           is of the form "facility.priority", then stderr is sent to syslog(3). Otherwise, stderr is appended
           to the file whose path is given in spec. By default, stderr is discarded unless the --foreground
           option is present, in this case, the client's stderr is propagated to daemon's stderr.

       --running
           Check whether or not a named daemon is running, then exit(3) with EXIT_SUCCESS if the named daemon is
           running or EXIT_FAILURE if it isn't. If the --verbose option is supplied, print a message before
           exiting. This option can only be used with the --name option. Note that the --chroot, --user, --name,
           --pidfiles and --pidfile (and possibly --config) options must be the same as for the target daemon.
           Note that the --running option must appear before any --pidfile or --pidfiles option when checking if
           another user's daemon is running otherwise you might get an error about the pidfile directory not
           being writable.

       --restart
           Instruct a named daemon to terminate and restart its client process. This option can only be used
           with the --name option. Note that the --chroot, --user, --name, --pidfiles and --pidfile (and
           possibly --config) options must be the same as for the target daemon.

       --stop
           Stop a named daemon then exit(3). This option can only be used with the --name option. Note that the
           --chroot, --user, --name, --pidfiles and --pidfile (and possibly --config) options must be the same
           as for the target daemon.

       As with all other programs, a -- argument signifies the end of options.  Any options that appear on the
       command line after -- are part of the client command.

FILES

       /etc/daemon.conf, ~/.daemonrc - define default options

       Each line of the configuration file consists of a client name or '*', followed by whitespace, followed by
       a comma separated list of options. Blank lines and comments ('#' to end of the line) are ignored. Lines
       may be continued with a '\' character at the end of the line.

       For example:

           *       errlog=daemon.err,output=local0.err,core
           test1   syslog=local0.debug,debug=9,verbose=9,respawn
           test2   syslog=local0.debug,debug=9,verbose=9,respawn

       The command line options are processed first to look for a --config option. If no --config option was
       supplied, the default file, /etc/daemon.conf, is used. If the user has their own configuration file
       (~/.daemonrc) it is also used. If the configuration files contain any generic ('*') entries, their
       options are applied in order of appearance.  If the --name option was supplied and the configuration
       files contain any entries with the given name, their options are then applied in order of appearance.
       Finally, the command line options are applied again. This ensures that any generic options apply to all
       clients by default. Client specific options override generic options. User options override system wide
       options. Command line options override everything else.

       Note that the configuration files are not opened and read until after any --chroot and/or --user command
       line options are processed. This means that the configuration file paths and the client's file path must
       be relative to the --chroot argument. It also means that the configuration files and the client
       executable must be readable/executable by the user specified by the --user argument. It also means that
       the --chroot and --user options must not appear in the configuration file. Also note that the --name must
       not appear in the configuration file either.

BUGS

       If you specify (in a configuration file) that all clients allow core file generation, there is no way to
       countermand that for any client (without using an alternative configuration file). So don't do that. The
       same applies to respawning and foreground.

       It is possible for the client process to obtain a controlling terminal under BSD. If anything calls
       open(2) on a terminal device without the O_NOCTTY flag, the process doing so will obtain a controlling
       terminal and then be susceptible to unintended termination by a SIGHUP.

       Clients run in the foreground with a pseudo terminal don't respond to job control (i.e. suspending with
       Control-Z doesn't work). This is because the client belongs to an orphaned process group (it starts in
       its own process session) so the kernel won't send it SIGSTOP signals. However, if the client is a shell
       that supports job control, it's subprocesses can be suspended.

       Clients can only be restarted if they were started with the --respawn option. Using --restart on a non-
       respawning daemon client is equivalent to using --stop.

MAILING LISTS

       The following mailing lists exist for daemon related discussion:

        daemon-announce@libslack.org - Announcements
        daemon-users@libslack.org    - User forum
        daemon-dev@libslack.org      - Development forum

       To subscribe to any of these mailing lists, send a mail message to listname-request@libslack.org with
       subscribe as the message body.  e.g.

        $ echo subscribe | mail daemon-announce-request@libslack.org
        $ echo subscribe | mail daemon-users-request@libslack.org
        $ echo subscribe | mail daemon-dev-request@libslack.org

       Or you can send a mail message to majordomo@libslack.org with subscribe listname in the message body.
       This way, you can subscribe to multiple lists at the same time.  e.g.

        $ mail majordomo@libslack.org
        subscribe daemon-announce
        subscribe daemon-users
        subscribe daemon-dev
        .

       A digest version of each mailing list is also available. Subscribe to digests as above but append -digest
       to the listname.

SEE ALSO

       libslack(3), daemon(3), coproc(3), pseudo(3), init(8), inetd(8), fork(2), umask(2), setsid(2), chdir(2),
       chroot(2), setrlimit(2), setgid(2), setuid(2), setgroups(2), initgroups(3), syslog(3), kill(2)

AUTHOR

       20100612 raf <raf@raf.org>