--- name: "init" section: "8" platform: "freebsd" package: "base" version: "16.0-CURRENT-20261027-61c70dc16a79" release: "FreeBSD 16.0-CURRENT (2026-10-27)" platforms: ["linux", "freebsd", "openbsd"] url: "https://new.carta.tech/init/8" --- # init(8) process control initialization ## NAME **init** – process control initialization ## SYNOPSIS **init** **init**\[ **0** \| **1** \| **6** \| **c** \| **q**\] ## DESCRIPTION The **init** utility is the last stage of the boot process. It normally runs the automatic reboot sequence as described in [rc(8)](/rc/8.md), and if this succeeds, begins multi-user operation. If the reboot scripts fail, **init** commences single-user operation by giving the super-user a shell on the console. The **init** utility may be passed parameters from the boot program to prevent the system from going multi-user and to instead execute a single-user shell without starting the normal daemons. The system is then quiescent for maintenance work and may later be made to go to multi-user by exiting the single-user shell (with ^D). This causes **init** to run the */etc/rc* start up command file in fastboot mode (skipping disk checks). If the *console* entry in the [ttys(5)](/ttys/5.md) file is marked “insecure”, then **init** will require that the super-user password be entered before the system will start a single-user shell. The password check is skipped if the *console* is marked as “secure”. Note that the password check does not protect from variables such as *init\_script* being set from the [loader(8)](/loader/8.md) command line; see the SECURITY section of [loader(8)](/loader/8.md). If the system security level (see [security(7)](/security/7.md)) is initially nonzero, then **init** leaves it unchanged. Otherwise, **init** raises the level to 1 before going multi-user for the first time. Since the level cannot be reduced, it will be at least 1 for subsequent operation, even on return to single-user. If a level higher than 1 is desired while running multi-user, it can be set before going multi-user, e.g., by the startup script [rc(8)](/rc/8.md), using [sysctl(8)](/sysctl/8.md) to set the *kern.securelevel* variable to the required security level. If **init** is run in a jail, the security level of the “host system” will not be affected. Part of the information set up in the kernel to support a jail is a per-jail security level. This allows running a higher security level inside of a jail than that of the host system. See [jail(8)](/jail/8.md) for more information about jails. In multi-user operation, **init** maintains processes for the terminal ports found in the file [ttys(5)](/ttys/5.md). The **init** utility reads this file and executes the command found in the second field, unless the first field refers to a device in */dev* which is not configured. The first field is supplied as the final argument to the command. This command is usually [getty(8)](/getty/8.md); **getty** opens and initializes the tty line and executes the [login(1)](/login/1.md) program. The **login** program, when a valid user logs in, executes a shell for that user. When this shell dies, either because the user logged out or an abnormal termination occurred (a signal), the cycle is restarted by executing a new **getty** for the line. The **init** utility can also be used to keep arbitrary daemons running, automatically restarting them if they die. In this case, the first field in the [ttys(5)](/ttys/5.md) file must not reference the path to a configured device node and will be passed to the daemon as the final argument on its command line. This is similar to the facility offered in the AT&T System V UNIX */etc/inittab*. Line status (on, off, secure, getty, or window information) may be changed in the [ttys(5)](/ttys/5.md) file without a reboot by sending the signal SIGHUP to **init** with the command “kill -HUP 1”. On receipt of this signal, **init** re-reads the [ttys(5)](/ttys/5.md) file. When a line is turned off in [ttys(5)](/ttys/5.md), **init** will send a SIGHUP signal to the controlling process for the session associated with the line. For any lines that were previously turned off in the [ttys(5)](/ttys/5.md) file and are now on, **init** executes the command specified in the second field. If the command or window field for a line is changed, the change takes effect at the end of the current login session (e.g., the next time **init** starts a process on the line). If a line is commented out or deleted from [ttys(5)](/ttys/5.md), **init** will not do anything at all to that line. The **init** utility will terminate multi-user operations and resume single-user mode if sent a terminate (TERM) signal, for example, “kill -TERM 1”. If there are processes outstanding that are deadlocked (because of hardware or software failure), **init** will not wait for them all to die (which might take forever), but will time out after 30 seconds and print a warning message. The **init** utility will cease creating new processes and allow the system to slowly die away, if it is sent a terminal stop (TSTP) signal, i.e. “kill -TSTP 1”. A later hangup will resume full multi-user operations, or a terminate will start a single-user shell. This hook is used by [reboot(8)](/reboot/8.md) and [halt(8)](/halt/8.md). The **init** utility will terminate all possible processes (again, it will not wait for deadlocked processes) and reboot the machine if sent the interrupt (INT) signal, i.e. “kill -INT 1”. This is useful for shutting the machine down cleanly from inside the kernel or from X when the machine appears to be hung. The **init** utility will do the same, except it will halt the machine if sent the user defined signal 1 (USR1), or will halt and turn the power off (if hardware permits) if sent the user defined signal 2 (USR2). When shutting down the machine, **init** will try to run the */etc/rc.shutdown* script. This script can be used to cleanly terminate specific programs such as **innd** (the InterNetNews server). If this script does not terminate within 120 seconds, **init** will terminate it. The timeout can be configured via the [sysctl(8)](/sysctl/8.md) variable *kern.init\_shutdown\_timeout*. **init** passes “single” as the argument to the shutdown script if return to single-user mode is requested. Otherwise, “reboot” argument is used. After all user processes have been terminated, **init** will try to run the */etc/rc.final* script. This script can be used to finally prepare and unmount filesystems that may have been needed during shutdown, for instance. The role of **init** is so critical that if it dies, the system will reboot itself automatically. If, at bootstrap time, the **init** process cannot be located, the system will panic with the message “panic: init died (signal %d, exit %d)”. If run as a user process as shown in the second synopsis line, **init** will emulate AT&T System V UNIX behavior, i.e., super-user can specify the desired *run-level* on a command line, and **init** will signal the original (PID 1) **init** as follows: | | | | | --- | --- | --- | | **Run-level** | Signal | Action | | **0** | SIGUSR1 | Halt | | **0** | SIGUSR2 | Halt and turn the power off | | **0** | SIGWINCH | Halt and turn the power off and then back on | | **1** | SIGTERM | Go to single-user mode | | **6** | SIGINT | Reboot the machine | | **c** | SIGTSTP | Block further logins | | **q** | SIGHUP | Rescan the | ## KERNEL ENVIRONMENT VARIABLES The following [kenv(2)](/kenv/2.md) variables are available as [loader(8)](/loader/8.md) tunables: - *init\_chroot* If set to a valid directory in the root file system, it causes **init** to perform a [chroot(2)](/chroot/2.md) operation on that directory, making it the new root directory. That happens before entering single-user mode or multi-user mode (but after executing the *init\_script* if enabled). This functionality has generally been eclipsed by rerooting. See [reboot(8)](/reboot/8.md) **-r** for details. - *init\_exec* If set to a valid file name in the root file system, instructs **init** to directly execute that file as the very first action, replacing **init** as PID 1. - *init\_script* If set to a valid file name in the root file system, instructs **init** to run that script as the very first action, before doing anything else. Signal handling and exit code interpretation is similar to running the */etc/rc* script. In particular, single-user operation is enforced if the script terminates with a non-zero exit code, or if a SIGTERM is delivered to the **init** process (PID 1). This functionality has generally been eclipsed by rerooting. See [reboot(8)](/reboot/8.md) **-r** for details. - *init\_shell* Defines the shell binary to be used for executing the various shell scripts. The default is “/bin/sh”. It is used for running the *init\_exec* or *init\_script* if set, as well as for the */etc/rc*, */etc/rc.shutdown*, and */etc/rc.final* scripts. The value of the corresponding [kenv(2)](/kenv/2.md) variable is evaluated every time **init** calls a shell script, so it can be changed later on using the [kenv(1)](/kenv/1.md) utility. In particular, if a non-default shell is used for running an *init\_script*, it might be desirable to have that script reset the value of *init\_shell* back to the default, so that the */etc/rc* script is executed with the standard shell */bin/sh*. - *init\_rc* If set to a valid file name in the root file system, overrides the default path to [rc(8)](/rc/8.md) (*/etc/rc*). This is useful for testing alternative service managers without modifying the default */etc/rc*. - *init\_path* Specifies the path used to search for the init binary. More than one binary can be listed in the string, candidate file names are split by the “:” separator. Each name is opened in sequence until a valid executable is found. ## RECOVERING If the */sbin/init* binary is broken or cannot be executed by the current kernel, recovery requires console access. Then, the *init\_path* loader tunable can be used to specify alternative **init** location. By default, system install leaves copy of the previous **init** binary at */sbin/init.bak*, and this path is set as one component of the default *init\_path*. If **init** cannot be run, the FreeBSD version of [sh(1)](/sh/1.md) has a special provision for running as PID 1. If the shell detects that it is running as init, it opens */dev/console* as it standard input and output and enters the command loop. The session should be exited using **reboot** **-q** or exec-ing fixed **init**, since a normal exit will cause a kernel panic. ## FILES - */dev/console* system console device - */dev/tty\** terminal ports found in [ttys(5)](/ttys/5.md) - */etc/ttys* the terminal initialization information file - */etc/rc* system startup commands - */etc/rc.shutdown* system shutdown commands - */etc/rc.final* system shutdown commands (after process termination) - */var/log/init.log* log of [rc(8)](/rc/8.md) output if the system console device is not available ## DIAGNOSTICS - getty repeating too quickly on port %s, sleeping. A process being started to service a line is exiting quickly each time it is started. This is often caused by a ringing or noisy terminal line. Init will sleep for 30 seconds, then continue trying to start the process. - some processes would not die; ps axl advised. A process is hung and could not be killed when the system was shutting down. This condition is usually caused by a process that is stuck in a device driver because of a persistent device error condition. ## SEE ALSO [kill(1)](/kill/1.md), [login(1)](/login/1.md), [sh(1)](/sh/1.md), [ttys(5)](/ttys/5.md), [security(7)](/security/7.md), [getty(8)](/getty/8.md), [halt(8)](/halt/8.md), [jail(8)](/jail/8.md), [rc(8)](/rc/8.md), [reboot(8)](/reboot/8.md), [shutdown(8)](/shutdown/8.md), [sysctl(8)](/sysctl/8.md) ## HISTORY An **init** utility appeared in Version 1 AT&T UNIX. ## CAVEATS Systems without [sysctl(8)](/sysctl/8.md) behave as though they have security level -1. Setting the security level above 1 too early in the boot sequence can prevent [fsck(8)](/fsck/8.md) from repairing inconsistent file systems. The preferred location to set the security level is at the end of */etc/rc* after all multi-user startup actions are complete.