1.\" Copyright (c) 1999 Berkeley Software Design, Inc. All rights reserved. 2.\" 3.\" Redistribution and use in source and binary forms, with or without 4.\" modification, are permitted provided that the following conditions 5.\" are met: 6.\" 1. Redistributions of source code must retain the above copyright 7.\" notice, this list of conditions and the following disclaimer. 8.\" 2. Redistributions in binary form must reproduce the above copyright 9.\" notice, this list of conditions and the following disclaimer in the 10.\" documentation and/or other materials provided with the distribution. 11.\" 3. Berkeley Software Design Inc's name may not be used to endorse or 12.\" promote products derived from this software without specific prior 13.\" written permission. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.Dd August 13, 2026 28.Dt DAEMON 8 29.Os 30.Sh NAME 31.Nm daemon 32.Nd run detached from the controlling terminal 33.Sh SYNOPSIS 34.Nm 35.Op Fl cfHrSx 36.Op Fl p Ar child_pidfile 37.Op Fl P Ar supervisor_pidfile 38.Op Fl t Ar title 39.Op Fl u Ar user 40.Op Fl m Ar output_mask 41.Op Fl o Ar output_file 42.Op Fl s Ar syslog_priority 43.Op Fl T Ar syslog_tag 44.Op Fl l Ar syslog_facility 45.Op Fl R Ar restart_delay_seconds 46.Op Fl C Ar restart_count 47.Ar command arguments ... 48.Sh DESCRIPTION 49The 50.Nm 51utility detaches itself from the controlling terminal and 52executes the program specified by its arguments. 53Privileges may be lowered to the specified user. 54The output of the daemonized process may be redirected to syslog and to a 55log file. 56.Pp 57The options are as follows: 58.Bl -tag -width indent 59.It Fl C , Fl -restart-count Ar restart_count 60Restart the process at most 61.Ar restart_count 62times. 63When zero is specified, 64.Nm 65will exit. 66The maximum restart count is 67.Cm 128 . 68This option is used together with option 69.Fl -restart . 70.It Fl c , Fl -change-dir 71Change the current working directory to the root 72.Pq Dq Pa / . 73.It Fl f , Fl -close-fds 74Redirect standard input, standard output and standard error to 75.Pa /dev/null . 76When this option is used together with any of the options related to file 77or syslog output, the standard file descriptors are first redirected to 78.Pa /dev/null , 79then stdout and/or stderr is redirected to a file or to syslog as 80specified by the other options. 81.It Fl H , Fl -sighup 82Close 83.Pa output_file 84and re-open it when signal 85.Dv SIGHUP 86is received, for interoperability with 87.Xr newsyslog 8 88and similar log rotation / archival mechanisms. 89If 90.Fl -output-file 91is not specified, this flag is ignored. 92.It Fl l , Fl -syslog-facility Ar syslog_facility 93These facilities are accepted: 94.Cm auth , authpriv , console , cron , daemon , 95.Cm ftp , kern , lpr , mail , news , ntp , security , 96.Cm syslog , user , uucp , 97and 98local facilities from 99.Cm local0 100to 101.Cm local7 . 102The default is 103.Cm daemon . 104.It Fl m , Fl -output-mask Ar output_mask 105Redirect output from the child process stdout 106.Pq Cm 1 , 107stderr 108.Pq Cm 2 , 109or both 110.Pq Cm 3 . 111This value specifies what is sent to syslog and the log file. 112The default is 113.Cm 3 . 114.It Fl M , Fl -output-file-mode Ar mode 115Specify the file 116.Ar mode 117to use when creating the 118.Pa output_file . 119The mode is interpreted using 120.Xr chmod 1 121style semantics. 122This option is useful when the daemonized process or external log 123collectors require group or world access to the output file. 124The default is 125.Cm 0600 . 126.It Fl o , Fl -output-file Ar output_file 127Append output from the daemonized process to 128.Pa output_file . 129If the file does not exist, it is created with the default file 130.Ar mode . 131When this option is used together with options 132.Fl -change-dir 133and 134.Fl -sighup 135the absolute path needs to be provided to ensure 136.Nm 137can re-open the file after a 138.Dv SIGHUP . 139.It Fl P , Fl -supervisor-pidfile Ar supervisor_pidfile 140Write the ID of the 141.Nm 142process into the 143.Ar supervisor_pidfile 144using the 145.Xr pidfile 3 146functionality. 147The program is executed in a spawned child process while the 148.Nm 149waits until it terminates to keep the 150.Ar supervisor_pidfile 151locked and removes it after the process exits. 152The 153.Ar supervisor_pidfile 154owner is the user who runs the 155.Nm 156regardless of whether the 157.Fl -user 158option is used or not. 159.It Fl p , Fl -child-pidfile Ar child_pidfile 160Write the ID of the created process into the 161.Ar child_pidfile 162using the 163.Xr pidfile 3 164functionality. 165The program is executed in a spawned child process while the 166.Nm 167waits until it terminates to keep the 168.Ar child_pidfile 169locked and removes it after the process exits. 170The 171.Ar child_pidfile 172owner is the user who runs the 173.Nm 174regardless of whether the 175.Fl -user 176option is used or not. 177.It Fl R , Fl -restart-delay Ar restart_delay_seconds 178Supervise and restart the program after the specified delay 179if it has been terminated. 180Valid values are 1-31536000 (up to 1 year). 181.It Fl r , Fl -restart 182Supervise and restart the program after a one-second delay if it has 183been terminated. 184.It Fl S , Fl -syslog 185Enable syslog output. 186This is implicitly applied if other syslog parameters are provided. 187The default values are daemon, notice, and daemon for facility, priority, and 188tag, respectively. 189.It Fl s , Fl -syslog-priority Ar syslog_priority 190These priorities are accepted: 191.Cm emerg , alert , crit , err , warning , 192.Cm notice , info , 193and 194.Cm debug . 195The default is 196.Cm notice . 197.It Fl T , Fl -syslog-tag Ar syslog_tag 198Set the tag which is appended to all syslog messages. 199The default is 200.Cm daemon . 201.It Fl t , Fl -title Ar title 202Set the title for the daemon process. 203The default is the daemonized invocation. 204.It Fl u , Fl -user Ar user 205Login name of the user to execute the program under. 206Environment variables 207.Ev HOME , USER , 208and 209.Ev SHELL 210are set accordingly. 211Requires adequate superuser privileges. 212.It Fl x , Fl -execute-only 213Do not supervise the child process when using 214.Fl p . 215This option is useful to run the given program as another user when 216.Xr su 1 217can't be used but a file holding the pid is needed. 218The 219.Ar child_pidfile 220will not be locked and the contents may be silently truncated by 221a concurrent daemon(8) invocation. 222.El 223.Pp 224If any of the options 225.Fl -child-pidfile 226(without 227.Fl -execute-only 228), 229.Fl -output-mask , 230.Fl -restart , 231.Fl -restart-delay , 232.Fl -supervisor-pidfile , 233.Fl -syslog , 234.Fl -syslog-facility 235.Fl -syslog-priority , 236.Fl -syslog-tag , 237or 238.Fl -output , 239are specified, the program is executed in a spawned child process. 240The 241.Nm 242waits until it terminates to keep the pid file(s) locked and removes them 243after the process exits or restarts the program. 244In this case if the monitoring 245.Nm 246receives software termination signal 247.Pq Dv SIGTERM 248it forwards it to the 249spawned process. 250Normally it will cause the child to exit, remove the pidfile(s) 251and then terminate. 252.Pp 253If neither file or syslog output are selected, all output is redirected to the 254.Nm 255process and written to stdout. 256The 257.Fl -close-fds 258option may be used to suppress the stdout output completely. 259.Pp 260The 261.Fl -supervisor-pidfile 262option is useful combined with the 263.Fl -restart 264option as 265.Ar supervisor_pidfile 266contains the ID of the supervisor 267not the child. 268This is especially important if you use 269.Fl -restart 270in an rc script as the 271.Fl -child-pidfile 272option will give you the child's ID to signal when you attempt to 273stop the service, causing 274.Nm 275to restart the child. 276.Sh EXIT STATUS 277The 278.Nm 279utility exits 1 if an error is returned by the 280.Xr daemon 3 281library routine, 2 if 282.Ar child_pidfile 283or 284.Ar supervisor_pidfile 285is requested, but cannot be opened, 3 if process is already running (pidfile 286exists and is locked), 4 if 287.Ar syslog_priority 288is not accepted, 5 if 289.Ar syslog_facility 290is not accepted, 6 if 291.Ar output_mask 292is not within the accepted range, 7 if 293.Ar output_file 294cannot be opened for appending, and otherwise 0. 295.Sh DIAGNOSTICS 296If the command cannot be executed, an error message is printed to 297standard error. 298The exact behavior depends on the logging parameters and the 299.Fl -close-fds 300flag. 301.Sh SEE ALSO 302.Xr nohup 1 , 303.Xr setregid 2 , 304.Xr setreuid 2 , 305.Xr daemon 3 , 306.Xr exec 3 , 307.Xr pidfile 3 , 308.Xr termios 4 , 309.Xr tty 4 310.Sh HISTORY 311The 312.Nm 313utility first appeared in 314.Fx 4.7 . 315