mirror of
https://github.com/troglobit/finit.git
synced 2026-10-01 13:33:09 +07:00
Joachim Wiberg
57c97d8190
This adds support for bringing up the system with an alternate fstab at boot. E.g., when using a primary/secondary setup for boot partitions. By default /etc/fstab is read, like before, this can now be changed using configure --with-fstab=/path/to/fstab.primary, which sets the default that can be overridden using finit.fstab=/etc/fstab.secondary If mounting, or fsck, fails in any way, Finit calls its own bundled sulogin, or the system sulogin(8), to let the user handle the issue. If there is no sulogin available, Finit will try to start up in its rescue.conf boot mode. Please note, in either of these rescue modes, use `reboot -f` to get the system to reboot. Finit is on pause in the background in rescue mode and cannot be relied on (since there may not be any writable filesystems available.). Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
262 lines
7.2 KiB
Plaintext
262 lines
7.2 KiB
Plaintext
.\" Hey, EMACS: -*- nroff -*-
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.\" First parameter, NAME, should be all caps
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.\" Second parameter, SECTION, should be 1-8, maybe w/ subsection
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.\" other parameters are allowed: see man(7), man(1)
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.Dd June 6, 2021
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.\" Please adjust this date whenever revising the manpage.
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.Dt FINIT 8 SMM
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.Os Linux
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.Sh NAME
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.Nm finit
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.Nd Fast init for Linux systems
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.Sh SYNOPSIS
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.Nm /sbin/finit
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.Op --
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.Op finit.debug
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.Op finit.fstab=/etc/fstab.alt
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.Op finit.status=<on,off>
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.Op finit.status_style=<classic,modern>
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.Op rescue | recover
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.Op single | S
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.Nm /sbin/telinit
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.Op Fl hv
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.Op q | Q | 0-9
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.Sh DESCRIPTION
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Fast init for Linux systems. Reverse engineered from the EeePC
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fastinit, 10+ years ago by Claudio Matsuoka, "gaps filled with frog
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DNA ...". Focus is on small and embedded systems, although Finit is
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fully usable on server and desktop systems as well.
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.Pp
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Features include:
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.Bl -bullet -width 1n -compact
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.It
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Runlevels, defined per service
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.It
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One-shot tasks, services (daemons), or SysV init start/stop scripts
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.It
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Runparts and
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.Pa /etc/rc.local
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support
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.It
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Process supervision similar to
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.Xr systemd 8
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.It
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Sourcing environment files
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.It
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Conditions for network/process/custom dependencies
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.It
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Pre/Post script actions
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.It
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Tooling to enable/disable services
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.It
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Built-in getty
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.It
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Built-in watchdog, with support for hand-over to
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.Lk https://troglobit.com/watchdogd.html watchdogd
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.It
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Built-in support for Debian/BusyBox
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.Pa /etc/network/interfaces
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.It
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Cgroups v2, both configuration and monitoring in `initctl top`
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.It
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Plugin support for customization
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.It
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Proper rescue mode with bundled `sulogin` for protected maintenance shell
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.El
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.Sh BOOTPARAM
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.Nm
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support the following command line parameters to alter the behavior
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at boot. Notice the
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.Cm --
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separator needed to tell the kernel which paramters should be given to
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PID 1. For more information on this, and available kernel command line
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options, see
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.Xr bootparam 7 .
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.Bl -tag -width pid -offset indent
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.It Cm finit.debug
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Enable Finit debug messages on system console and log. Sometimes useful
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when doing board bringup. Before the system log daemon has started,
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Finit use the kernel ring buffer,
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.Pa /dev/kmsg .
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.It Cm finit.fstab=/path/to/fstab.alt
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Tell
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.Nm
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to use an alternate
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.Cm fstab
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to mount the file system from. Remember, this file must be on the
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.Cm root=...
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file system provided to Finit from the kernel. If this file is missing,
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.Nm
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falls back to its built-in default, which can be changed at build time
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using the
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.Cm --with-fstab=/path/to/footab
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configure option. It is even possible to completely disable the
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built-in using
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.Cm --without-fstab ,
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meaning
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.Nm
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.Sy must
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be started with the
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.Cm finit.fstab
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option.
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.Pp
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Should
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.Nm
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discover that there is no fstab file available, including the fallback,
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it triggers the same failure mode as when
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.Cm fsck
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fails, starting
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.Xr sulogin 8 ,
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if that is availble. When
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.Cm sulogin
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is missing, or when the user exits from
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.Cm sulogin ,
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the system is rebooted.
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.Pp
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Default fstab, unless changed at build-time:
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.Pa /etc/fstab
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.It Cm finit.status=<on,off>
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Control finit boot progress, including banner. This used to be called
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.Cm finit.show_status ,
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which still works but is deprecated.
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.It Cm finit.status_style=<classic,modern>
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Set Finit boot progress style, when enabled.
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.It Cm rescue | recover
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Start rescue/maintenance mode. If your system comes with the bundled
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.Cm sulogin
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program (Finit, or from util-linux/Busybox), you will be given a root
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login to a maintenance shell. However, if
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.Cm sulogin
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is missing, the file
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.Pa /lib/finit/rescue.conf
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is read and the system booted in a limited fallback mode. See
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.Xr finit.conf 5
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for more information.
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.It Cm single | S
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Single user mode, runlevel 1, in Finit. Useful to debug problems with
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the regular runlevel. All services and TTYs in
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.Cm [1]
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will be started, e.g., a
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.Cm tty [1] @console nologin
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configuration presents you with a root console without login.
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.El
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.Sh BOOTING
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.Pp
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Before laucnhing services, the system needs to be bootstrapped. This
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involves mounting all filesystems (not already mounted by an initramfs)
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in
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.Pa /etc/fstab ,
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or any alternate
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.Pa fstab
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file provided on the Finit command line using
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.Cm finit.fstab ,
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ensuring that necessary filesystems like:
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.Pa /dev ,
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.Pa /proc ,
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.Pa /sys ,
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and
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.Pa /run
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are available and can provide the system with the services required.
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.Pp
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With that out of the way, a set of plugins take over:
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.Pp
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.Bl -tag -width bootmisc.so -offset indent
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.It Cm bootmisc.so
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Cleans up stale files from previous boots and default directories are
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created in tmpfs filesystems
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.It Cm modprobe.so
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Probes kernel modules required by the system
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.It Cm procps.so
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Set kernel variables from
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.Pa /etc/sysctl.conf
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et al
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.El
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.Pp
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When the plugins are done, finit reads
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.Pa /etc/finit.conf
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and all other enabled services in
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.Pa /etc/finit.d/* .
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First all services, run/tasks in runlevel S (bootStrap) are started,
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When all run/tasks have completed, Finit changes to the configured
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runlevel (default 2), Processes are started in parallel, in dependency
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order according to their conditions.
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.Pp
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When all services and run/tasks have been started, the console progress
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is disabled and all configured getty services are started.
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.Sh CONDITIONS
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The condition subysystem in Finit was initially created to track PID
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files of daemons. If service/task B requires service A to have started,
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Finit waits for the PID file of service A to be created/updated before
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it starts service B. Conversely, if service A is stopped and its PID
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file removed, service B is also stopped.
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.Pp
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The following condition families are available today:
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.Pp
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.Bl -tag -width pid -offset indent
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.It Cm net
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Linux netlink events, e.g. net/route/default, net/eth0/up, and
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net/et0/running
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.It Cm pid
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PID files basd on the service declaration
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.Cm name:id ,
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gives the condition pid/name:id
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.It Cm sys
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System conditions, e.g. sys/key/ctrlaltdel and sys/pwr/fail
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.It Cm usr
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User conditions, assert and deassert using
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.Cm initctl cond [set|clr] foo
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.El
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.Sh SIGNALS
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PID 1 is the only process that by default blocks all signals. Finit
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allows for the following signals to control operation, but recommends
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instead using the
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.Xr initctl 8
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tool.
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.Pp
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.Bl -tag -width TERM
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.It HUP
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Tell
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.Nm
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to reload its configuration file(s), same as
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.Cm initctl reload
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.It USR1
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Restart API
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.Cm ( initctl )
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socket.
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.It USR2
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Tell
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.Nm
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to perform a system shutdown, same as
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.Cm initctl poweroff
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.It TERM
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Like SIGUSR2 but performs a reboot, same as
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.Cm initctl reboot
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.It INT
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Sent from kernel when Ctrl-Alt-Del is pressed (on the console), this
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asserts the sys/key/ctrlaltdel condition, which can be used to start
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tasks or services
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.It PWR
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Sent from a a power daemon on changes to UPS status, Finit asserts
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the sys/pwr/fail condition
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.El
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.Sh FILES
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.Bl -tag -width /etc/finit.d/available/*.conf -compact
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.It Pa /etc/finit.conf
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Main configuration file
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.It Pa /etc/finit.d/*.conf
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Static service definitions
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.It Pa /etc/finit.d/available/*.conf
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Available services
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.It Pa /etc/finit.d/enabled/*.conf
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Symlinks from available
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.It Pa /run/finit/
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Runtime files, including the condition subsystem
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.El
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.Sh SEE ALSO
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.Xr finit.conf 5
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.Xr initctl 8
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.Sh AUTHORS
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.Nm
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was conceived and reverse engineered by Claudio Matsuoka. Since v1.0,
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maintained by Joachim Wiberg, with contributions by many others.
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