freebsd-skq/usr.sbin/daemon/daemon.8

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.Dd September 22, 2020
.Dt DAEMON 8
.Os
.Sh NAME
.Nm daemon
.Nd run detached from the controlling terminal
.Sh SYNOPSIS
.Nm
.Op Fl cfHrS
.Op Fl p Ar child_pidfile
.Op Fl P Ar supervisor_pidfile
.Op Fl t Ar title
.Op Fl u Ar user
.Op Fl m Ar output_mask
.Op Fl o Ar output_file
.Op Fl s Ar syslog_priority
.Op Fl T Ar syslog_tag
.Op Fl l Ar syslog_facility
.Op Fl R Ar restart_delay_seconds
.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.
The output of the daemonized process may be redirected to syslog and to a
log file.
.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 .
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
.Pa /dev/null ,
then stdout and/or stderr is redirected to a file or to syslog as
specified by the other options.
.It Fl H
Close
.Pa output_file
and re-open it when signal SIGHUP is received, for interoperability with
.Xr newsyslog 1
and similar log rotation / archival mechanisms.  If
.Fl o
is not specified, this flag is ignored.
.It Fl 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.
.It Fl o Ar output_file
Append output from the daemonized process to
.Pa output_file .
If the file does not exist, it is created with permissions 0600.
When this option is used together with options
.Fl c and
.Fl H
the absolute path needs to be provided to ensure
.Nm
can re-open the file after a SIGHUP.
.It Fl m Ar 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.
.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 after a one-second delay if it has
been terminated.
.It Fl R Ar restart_delay_seconds
Supervise and restart the program after the specified delay
if it has been terminated.
.It Fl t Ar title
Set the title for the daemon process.
The default is the daemonized invocation.
.It Fl u Ar user
Login name of the user to execute the program under.
Requires adequate superuser privileges.
.It Fl s Ar syslog_priority
These priorities are accepted: emerg, alert, crit, err, warning,
notice, info, and debug.
The default is notice.
.It Fl l Ar 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.
.It Fl T Ar syslog_tag
Set the tag which is appended to all syslog messages.
The default is daemon.
.El
.Pp
If any of the options
.Fl p ,
.Fl P ,
.Fl r ,
.Fl o ,
.Fl s ,
.Fl T ,
.Fl m ,
.Fl S ,
or
.Fl l
are 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
If neither file or syslog output are selected, all output is redirected to the
.Nm
process and written to stdout.
The
.Fl f
option may be used to suppress the stdout output completely.
.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), 4 if
.Ar syslog_priority
is not accepted, 5 if
.Ar syslog_facility
is not accepted, 6 if
.Ar output_mask
is not within the accepted range, 7 if
.Ar output_file
cannot be opened for appending, and otherwise 0.
.Sh 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
.Fl f
flag.
.Sh SEE ALSO
.Xr nohup 1 ,
.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 .