DAEMON(8)               FreeBSD System Manager's Manual              DAEMON(8)

NAME
     daemon - run detached from the controlling terminal

SYNOPSIS
     daemon [-cfHrS] [-p child_pidfile] [-P supervisor_pidfile] [-t title]
            [-u user] [-m output_mask] [-o output_file] [-s syslog_priority]
            [-T syslog_tag] [-l syslog_facility] [-R restart_delay_seconds]
            command arguments ...

DESCRIPTION
     The daemon utility detaches itself from the controlling terminal and
     executes the program specified by its arguments.  Privileges may be
     lowered to the specified user.  The output of the daemonized process may
     be redirected to syslog and to a log file.

     The options are as follows:

     -c      Change the current working directory to the root ("/").

     -f      Redirect standard input, standard output and standard error to
             /dev/null.  When this option is used together with any of the
             options related to file or syslog output, the standard file
             descriptors are first redirected to /dev/null, then stdout and/or
             stderr is redirected to a file or to syslog as specified by the
             other options.

     -H      Close output_file and re-open it when signal SIGHUP is received,
             for interoperability with newsyslog(1) and similar log rotation /
             archival mechanisms.  If -o is not specified, this flag is
             ignored.

     -S      Enable syslog output.  This is implicitly applied if other syslog
             parameters are provided.  The default values are daemon, notice,
             and daemon for facility, priority, and tag, respectively.

     -o output_file
             Append output from the daemonized process to output_file.  If the
             file does not exist, it is created with permissions 0600.  When
             this option is used together with options -c and -H the absolute
             path needs to be provided to ensure daemon can re-open the file
             after a SIGHUP.

     -m output_mask
             Redirect output from the child process stdout (1), stderr (2), or
             both (3).  This value specifies what is sent to syslog and the
             log file.  The default is 3.

     -p child_pidfile
             Write the ID of the created process into the child_pidfile using
             the pidfile(3) functionality.  The program is executed in a
             spawned child process while the daemon waits until it terminates
             to keep the child_pidfile locked and removes it after the process
             exits.  The child_pidfile owner is the user who runs the daemon
             regardless of whether the -u option is used or not.

     -P supervisor_pidfile
             Write the ID of the daemon process into the supervisor_pidfile
             using the pidfile(3) functionality.  The program is executed in a
             spawned child process while the daemon waits until it terminates
             to keep the supervisor_pidfile locked and removes it after the
             process exits.  The supervisor_pidfile owner is the user who runs
             the daemon regardless of whether the -u option is used or not.

     -r      Supervise and restart the program after a one-second delay if it
             has been terminated.

     -R restart_delay_seconds
             Supervise and restart the program after the specified delay if it
             has been terminated.

     -t title
             Set the title for the daemon process.  The default is the
             daemonized invocation.

     -u user
             Login name of the user to execute the program under.  Requires
             adequate superuser privileges.

     -s syslog_priority
             These priorities are accepted: emerg, alert, crit, err, warning,
             notice, info, and debug.  The default is notice.

     -l syslog_facility
             These facilities are accepted: auth, authpriv, console, cron,
             daemon, ftp, kern, lpr, mail, news, ntp, security, syslog, user,
             uucp, and local0, ..., local7.  The default is daemon.

     -T syslog_tag
             Set the tag which is appended to all syslog messages.  The
             default is daemon.

     If any of the options -p, -P, -r, -o, -s, -T, -m, -S, or -l are
     specified, the program is executed in a spawned child process.  The
     daemon waits until it terminates to keep the pid file(s) locked and
     removes them after the process exits or restarts the program.  In this
     case if the monitoring daemon receives software termination signal
     (SIGTERM) it forwards it to the spawned process.  Normally it will cause
     the child to exit, remove the pidfile(s) and then terminate.

     If neither file or syslog output are selected, all output is redirected
     to the daemon process and written to stdout.  The -f option may be used
     to suppress the stdout output completely.

     The -P option is useful combined with the -r option as supervisor_pidfile
     contains the ID of the supervisor not the child.  This is especially
     important if you use -r in an rc script as the -p option will give you
     the child's ID to signal when you attempt to stop the service, causing
     daemon to restart the child.

EXIT STATUS
     The daemon utility exits 1 if an error is returned by the daemon(3)
     library routine, 2 if child_pidfile or supervisor_pidfile is requested,
     but cannot be opened, 3 if process is already running (pidfile exists and
     is locked), 4 if syslog_priority is not accepted, 5 if syslog_facility is
     not accepted, 6 if output_mask is not within the accepted range, 7 if
     output_file cannot be opened for appending, and otherwise 0.

DIAGNOSTICS
     If the command cannot be executed, an error message is printed to
     standard error.  The exact behavior depends on the logging parameters and
     the -f flag.

SEE ALSO
     nohup(1), setregid(2), setreuid(2), daemon(3), exec(3), pidfile(3),
     termios(4), tty(4)

HISTORY
     The daemon utility first appeared in FreeBSD 4.7.

FreeBSD 13.1-RELEASE-p6        January 14, 2021        FreeBSD 13.1-RELEASE-p6