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
Thedaemon
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 ensuredaemon
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 thedaemon
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 thedaemon
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 thedaemon
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.