xref: /freebsd/usr.sbin/daemon/daemon.8 (revision 112bfcf5e4e4309afa9c8fcccd120e36fa2dd3fa)

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.Dd March 2, 2016
.Dt DAEMON 8
.Os
.Sh NAME
.Nm daemon
.Nd run detached from the controlling terminal
.Sh SYNOPSIS
.Nm
.Op Fl cfr
.Op Fl p Ar child_pidfile
.Op Fl P Ar supervisor_pidfile
.Op Fl t Ar title
.Op Fl u Ar user
.Ar command arguments ...
.Sh DESCRIPTION
The
.Nm
utility detaches itself from the controlling terminal and
executes the program specified by its arguments.
Privileges may be lowered to the specified user.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl c
Change the current working directory to the root
.Pq Dq Pa / .
.It Fl f
Redirect standard input, standard output and standard error to
.Pa /dev/null .
.It Fl p Ar child_pidfile
Write the ID of the created process into the
.Ar child_pidfile
using the
.Xr pidfile 3
functionality.
The program is executed in a spawned child process while the
.Nm
waits until it terminates to keep the
.Ar child_pidfile
locked and removes it after the process exits.
The
.Ar child_pidfile
owner is the user who runs the
.Nm
regardless of whether the
.Fl u
option is used or not.
.It Fl P Ar supervisor_pidfile
Write the ID of the
.Nm
process into the
.Ar supervisor_pidfile
using the
.Xr pidfile 3
functionality.
The program is executed in a spawned child process while the
.Nm
waits until it terminates to keep the
.Ar supervisor_pidfile
locked and removes it after the process exits.
The
.Ar supervisor_pidfile
owner is the user who runs the
.Nm
regardless of whether the
.Fl u
option is used or not.
.It Fl r
Supervise and restart the program if it has been terminated.
.It Fl t Ar title
Process title for the daemon to make it easily identifiable.
.It Fl u Ar user
Login name of the user to execute the program under.
Requires adequate superuser privileges.
.El
.Pp
If the
.Fl p ,
.Fl P
or
.Fl r
option is specified the program is executed in a spawned child process.
The
.Nm
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
.Nm
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.
.Pp
The
.Fl P
option is useful combined with the
.Fl r
option as
.Ar supervisor_pidfile
contains the ID of the supervisor
not the child.
This is especially important if you use
.Fl r
in an rc script as the
.Fl p
option will give you the child's ID to signal when you attempt to
stop the service, causing
.Nm
to restart the child.
.Sh EXIT STATUS
The
.Nm
utility exits 1 if an error is returned by the
.Xr daemon 3
library routine, 2 if
.Ar child_pidfile
or
.Ar supervisor_pidfile
is requested, but cannot be opened, 3 if process is already running (pidfile
exists and is locked),
otherwise 0.
.Sh DIAGNOSTICS
If the command cannot be executed, an error message is displayed on
standard error unless the
.Fl f
flag is specified.
.Sh SEE ALSO
.Xr setregid 2 ,
.Xr setreuid 2 ,
.Xr daemon 3 ,
.Xr exec 3 ,
.Xr pidfile 3 ,
.Xr termios 4 ,
.Xr tty 4
.Sh HISTORY
The
.Nm
utility first appeared in
.Fx 4.7 .