RC(8)

💅 RC(8) — command scripts for auto-reboot and daemon startup 💅

okay so bestie, welcome to RC(8) from the System Manager's Manual. This is highkey the whole “what runs when your box boots or shuts down” situation, and honestly it's giving main-character energy. Let's get into it. 🫶

🎀 NAME 🎀

• rc — command scripts for auto-reboot and daemon startup

🦋 SYNOPSIS 🦋

rc
rc.conf
rc.conf.local
rc.d/
rc.firewall
rc.local
rc.resume
rc.shutdown
rc.subr
rc.suspend

🌸 DESCRIPTION 🌸

The rc utility is the command script that controls the automatic boot process after init(8) calls it. The rc.local script holds commands that are only about a specific site. These days the /usr/local/etc/rc.d/ mechanism is usually used instead of rc.local, but if you want to use rc.local, it is still supported. In that case it should source /etc/rc.conf and contain extra custom startup code for your system. The best way to handle rc.local, though, is to split it out into rc.d/ style scripts and put them under /usr/local/etc/rc.d/. The rc.conf file has the global system configuration info that the startup scripts reference, while rc.conf.local holds the local system configuration. See rc.conf(5) for more info.

The rc.d/ directories contain scripts that get automatically executed at boot time and shutdown time. ✨

The service(8) command gives you a convenient interface to manage rc.d services. The sysrc(8) command gives you a scripting interface to modify system config files.

⚙️ Operation of rc ⚙️

Here's the boot-time sequence, step by step — no cap:

1. If autobooting, set autoboot=yes and enable a flag (rc_fast=yes), which prevents the rc.d/ scripts from doing the check for already running processes (so the boot process speeds up). This rc_fast=yes speedup will not happen when rc is started up after exiting the single-user shell.
2. Figure out whether the system is booting diskless, and if it is, run the /etc/rc.initdiskless script.
3. source /etc/rc.subr to load the various rc.subr(8) shell functions to use.
4. Load the configuration files (see below for reloading).
5. Determine if booting in a jail, and add “nojail” (no jails allowed) or “nojailvnet” (only allow vnet-enabled jails) to the list of KEYWORDS to skip in rcorder(8).
6. If the file ${firstboot_sentinel} does not exist, add “firstboot” to the list of KEYWORDS to skip in rcorder(8).
7. Invoke rcorder(8) to order the files in /etc/rc.d/ that do not have a “nostart” KEYWORD (refer to rcorder(8)'s -s flag).
8. Call run_rc_scripts() with the list of scripts to be run. For each script that will call run_rc_script() (both functions are from rc.subr(8)), which sets $1 to “start”, and sources the script in a subshell. Stop processing when the script that is the value of the $early_late_divider has been run.
9. Check again to see if the file ${firstboot_sentinel} exists (in case it is located on a newly mounted file system) and adjust the list of KEYWORDs to skip appropriately.
10. Re-run rcorder(8), this time including the scripts in the $local_startup directories. Call run_rc_scripts() again with the new list of scripts. It will skip any that have already been run and execute the rest as described above.
11. If the file ${firstboot_sentinel} exists, delete it. If the file ${firstboot_sentinel}-reboot also exists (because it was created by a script), then delete it and reboot.

🛑 Operation of rc.shutdown 🛑

Shutdown sequence, bestie — also step by step, and yes it ate:

1. Set rc_shutdown to the value of the first argument passed to rc.shutdown or to “unspecified” if no argument was passed.
2. source /etc/rc.subr to load the various rc.subr(8) shell functions to use.
3. Load the configuration files.
4. Invoke rcorder(8) to order the files in /etc/rc.d/ and the $local_startup directories that have a “shutdown” KEYWORD (refer to rcorder(8)'s -k flag), reverse that order, and assign the result to a variable.
5. Call each script in turn using run_rc_script() (from rc.subr(8)), which sets $1 to “faststop”, and sources the script in a subshell.

📁 Contents of rc.d/ 📁

rc.d/ is located in /etc/rc.d/. The following file naming conventions are currently used in rc.d/:

• ALLUPPERCASE — Scripts that are “placeholders” to make sure certain operations happen before others. In order of startup, these are:
  • FILESYSTEMS — Ensure that root and other critical file systems are mounted. This is the default $early_late_divider.
  • NETWORKING — Ensure basic network services are running, including general network configuration.
  • SERVERS — Ensure basic services exist for services that start early (such as nisdomain), because they are required by DAEMON below.
  • DAEMON — Check-point before all general purpose daemons such as lpd and ntpd.
  • LOGIN — Check-point before user login services (inetd and sshd), as well as services which might run commands as users (cron and sendmail).
• bar — Scripts that are sourced in a subshell. The boot does not stop if such a script terminates with a non-zero status, but a script can stop the boot if necessary by invoking the stop_boot() function (from rc.subr(8)).

Each script should contain rcorder(8) keywords, especially an appropriate “PROVIDE” entry, and if necessary “REQUIRE” and “BEFORE” keywords.

Each script is expected to support at least the following arguments, which are automatically supported if it uses the run_rc_command() function:

• start — Start the service. This should check that the service is to be started as specified by rc.conf(5). It also checks if the service is already running and refuses to start if it is. This latter check is not performed by standard FreeBSD scripts if the system is starting directly to multi-user mode, to speed up the boot process. If forcestart is given, ignore the rc.conf(5) check and start anyway.
• stop — If the service is to be started as specified by rc.conf(5), stop the service. This should check that the service is running and complain if it is not. If forcestop is given, ignore the rc.conf(5) check and attempt to stop.
• restart — Perform a stop then a start.
• status — If the script starts a process (rather than performing a one-off operation), show the status of the process. Otherwise it is not necessary to support this argument. Defaults to displaying the process ID of the program (if running).
• enable — Enable the service in rc.conf(5).
• disable — Disable the service in rc.conf(5).
• delete — Remove the service from rc.conf(5). If service_delete_empty is set to “YES”, /etc/rc.conf.d/$servicename will be deleted if empty after modification.
• describe — Print a short description of what the script does.
• extracommands — Print the script's non-standard commands.
• poll — If the script starts a process (rather than performing a one-off operation), wait for the command to exit. Otherwise it is not necessary to support this argument.
• enabled — Return 0 if the service is enabled and 1 if it is not. This command does not print anything.
• rcvar — Display which rc.conf(5) variables are used to control the startup of the service (if any).

If a script must implement additional commands it can list them in the extra_commands variable, and define their actions in a variable constructed from the command name (see the “EXAMPLES” section).

The configuration files are normally read only once at the start of a boot sequence; if a script needs to enable or disable any other script that would run later in the sequence, it must send a SIGALRM to the rc process (identified by $RC_PID) to have it re-read the files.

The following key points apply to old-style scripts in /usr/local/etc/rc.d/ — iykyk:

• Scripts are only executed if their basename(1) matches the shell globbing pattern *.sh, and they are executable. Any other files or directories present within the directory are silently ignored.
• When a script is executed at boot time, it is passed the string “start” as its first and only argument. At shutdown time, it is passed the string “stop” as its first and only argument. All rc.d/ scripts are expected to handle these arguments appropriately. If no action needs to be taken at a given time (either boot time or shutdown time), the script should exit successfully and without producing an error message.
• The scripts within each directory are executed in lexicographical order. If a specific order is required, numbers may be used as a prefix to the existing filenames, so for example 100.foo would be executed before 200.bar; without the numeric prefixes the opposite would be true.
• The output from each script is traditionally a space character, followed by the name of the software package being started or shut down, without a trailing newline character.

🌸 SCRIPTS OF INTEREST 🌸

Okay so when an automatic reboot is in progress, rc is invoked with the argument autoboot. One of the scripts run from /etc/rc.d/ is /etc/rc.d/fsck. This script runs fsck(8) with option -p and -F to “preen” all the disks of minor inconsistencies resulting from the last system shutdown. If this fails, then checks/repairs of serious inconsistencies caused by hardware or software failure will be performed in the background at the end of the booting process. If autoboot is not set — when going from single-user to multi-user mode for example — the script does not do anything. 💅

The /etc/rc.d/serial script is used to set any special configurations for serial devices. 🎀

The rc.firewall script is used to configure rules for the kernel based firewall service. It has several possible options:

• open — will allow anyone in
• client — will try to protect just this machine
• simple — will try to protect a whole network
• closed — totally disables IP services except via lo0 interface
• UNKNOWN — disables the loading of firewall rules
• filename — will load the rules in the given filename (full path required).

Most daemons, including network related daemons, have their own script in /etc/rc.d/, which can be used to start, stop, and check the status of the service. ✨

Any architecture specific scripts, such as /etc/rc.d/apm for example, specifically check that they are on that architecture before starting the daemon. 🦋

Following tradition, all startup files reside in /etc. 🫶

🎀 FILES 🎀

• /etc/rc
• /etc/rc.conf
• /etc/rc.conf.local
• /etc/rc.d/
• /etc/rc.firewall
• /etc/rc.local
• /etc/rc.shutdown
• /etc/rc.subr
• /var/run/dmesg.boot — dmesg(8) results soon after the rc process begins. Useful when dmesg(8) buffer in the kernel no longer has this information.

🦋 EXAMPLES 🦋

The following is a minimal rc.d/ style script. Most scripts require little more than the following.

#!/bin/sh
#

# PROVIDE: foo
# REQUIRE: bar_service_required_to_precede_foo

. /etc/rc.subr

name="foo"
rcvar=foo_enable
command="/usr/local/bin/foo"

load_rc_config $name
run_rc_command "$1"

Certain scripts may want to provide enhanced functionality. The user may access this functionality through additional commands. The script may list and define as many commands at it needs. 💖

#!/bin/sh
#

# PROVIDE: foo
# REQUIRE: bar_service_required_to_precede_foo
# BEFORE:  baz_service_requiring_foo_to_precede_it

. /etc/rc.subr

name="foo"
rcvar=foo_enable
command="/usr/local/bin/foo"
extra_commands="nop hello"
hello_cmd="echo Hello World."
nop_cmd="do_nop"

do_nop()
{
        echo "I do nothing."
}

load_rc_config $name
run_rc_command "$1"

As all processes are killed by init(8) at shutdown, the explicit kill(1) is unnecessary, but is often included. 😭

⭐ SEE ALSO ⭐

• kill(1)
• rc.conf(5)
• init(8)
• rc.resume(8)
• rc.subr(8)
• rcorder(8)
• reboot(8)
• savecore(8)
• service(8)
• sysrc(8)

Practical rc.d scripting in BSD, <https://docs.freebsd.org/en/articles/rc-scripting/>. 🧚

👑 HISTORY 👑

The rc utility appeared in 4.0BSD. 🔥

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Source/version and date tea: Debian, September 20, 2024 — RC(8) signing off with maximum sparkle. Byeee 💅🌈✨