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README: Further cleanup and refactoring

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Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
This commit is contained in:
Joachim Nilsson
2016-09-18 18:32:38 +02:00
parent 89105090ed
commit e8fa827026
2 changed files with 61 additions and 52 deletions
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README.md
+20 -52
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@@ -210,7 +210,7 @@ are used, and even more commonly, only the default runlevel is used.
To specify an allowed set of runlevels for a `service`, `run` command,
`task`, or `tty`, add `[NNN]` to your `/etc/finit.conf`, like this:
```shell
```
service [S12345] /sbin/syslogd -n -x -- System log daemon
run [S] /etc/init.d/acpid start -- Starting ACPI Daemon
task [S] /etc/init.d/kbd start -- Preparing console
@@ -247,47 +247,21 @@ start any new ones for you, without rebooting the system.
Rebooting & Halting
-------------------
Finit is often used on embedded and small Linux systems with BusyBox.
For compatibility with its existing toolset (halt, poweroff, reboot),
the following signals have been adopted:
Traditionally, rebooting and halting a UNIX system is done by changing
its runlevel. Finit comes with its own tooling providing: `shutdown`,
`reboot`, `poweroff`, and `suspend`, but also the traditional `init` and
`telinit`, as well as a more modern `initctl` tool, detailed in the next
section.
* `SIGUSR1`
Same effect as `finit q`, reloads all *.conf files in `/etc/finit.d/`
* `SIGUSR1`
Calls shutdown hooks, including HOOK_SHUTDOWN, stops all running
processes, and unmounts all file systems. Then tells kernel to
halt. Most people these days want SIGUSR2 though.
For compatibility reasons Finit listens to the same set of signals as
BusyBox init. This is not 100% compatible with SysV init, but clearly
the more common combination for Finit. For more details, see
[doc/signals.md](doc/signals.md).
SysV init and systemd use this to re-open their FIFO/D-Bus.
* `SIGUSR2`
Like SIGUSR1, but tell kernel to power-off the system, if ACPI
or similar exists to actually do this. If the kernel fails
power-off, Finit falls back to halt.
SysV init N/A, systemd dumps its internal state to log.
* `SIGTERM`
Like `SIGUSR1`, but tell kernel to reboot the system when done.
SysV init N/A, systemd rexecutes itself.
* `SIGINT`
Sent from kernel when the CTRL-ALT-DEL key combo is pressed.
SysV init and systemd default to reboot with `shutdown -r`.
Finit currently forwards this to `SIGTERM`.
* `SIGPWR`
Sent from a power daemon, like `powstatd(8)`, on changes to the
UPS status. Traditionally SysV init read /etc/powerstatus and
acted on "OK", "FAIL", or "LOW" and then removed the file.
Finit currently forwards this to `SIGUSR2`.
Finit also listens to the classic SysV init FIFO, used by `telinit`.
Support for this is implemented by the `initctl.so` plugin. Hence,
`telinit q` will work as the UNIX beards intended.
Finit also listens to the classic SysV init FIFO, which used to be
located in `/dev` but these days default to `/run/initctl`. Hence,
existing tools like, `poweroff`, `halt`, `reboot`, and `shutdown` work
as expected. Support for this old-style handling is implemented in the
optional `initctl.so` plugin and can be accessed with the traditional
`telinit` command line tool, symlinked to `finit`. Hence, if finit is
your system init, then `init q` will work as the UNIX beards intended.
```shell
~ # telinit -h
Usage: telinit [OPTIONS] [q | Q | 0-9]
@@ -303,7 +277,6 @@ your system init, then `init q` will work as the UNIX beards intended.
q, Q Reload *.conf in /etc/finit.d/, same as initctl reload or
sending SIGHUP to PID 1
1, s, S Enter system rescue mode, runlevel 1
```
Commands & Status
@@ -313,7 +286,6 @@ Finit also implements a more modern API to query status, and start/stop
services, called `initctl`. Unlike `telinit` the `initctl` tool does
not return until the given command has fully completed.
```shell
~ $ initctl -h
Usage: initctl [OPTIONS] <COMMAND>
@@ -337,21 +309,17 @@ not return until the given command has fully completed.
restart <JOB|NAME>[:ID] Restart (stop/start) service by job# or name
reload <JOB|NAME>[:ID] Reload (SIGHUP) service by job# or name
version Show Finit version
```
The `<!>` notation to a service stanza can be used empty, then it will
apply to `reload` and `runlevel` commands. I.e., when a service's
`.conf` file has been changed Finit will stop and start it instead. If
a service does *not* have `<!>` declared, the service will be reloaded
(`SIGHUP`:ed) in the `START` phase instead. The latter is the preferred
behaviour, but not all daemons support this, unfortunately.
For services *not* supporting `SIGHUP` the `<!>` notation in the .conf
file must be used to tell Finit to stop and start it on `reload` and
`runlevel` changes. If `<>` holds more [conditions](doc/conditions.md),
these will also affect how a service is maintained.
**Note:** even though it is possible to start services not belonging to
**Note:** even though it is possible to start services not belonging in
the current runlevel these services will not be respawned automatically
by Finit if they exit (crash). Hence, if the runlevel is 2, the below
Dropbear SSH service will not be restarted if it is killed or exits.
```shell
~ $ initctl status -v
1 running 476 [S12345] /sbin/watchdog -T 16 -t 2 -F /dev/watchdog
2 running 477 [S12345] /sbin/syslogd -n -b 3 -D
@@ -363,7 +331,7 @@ Dropbear SSH service will not be restarted if it is killed or exits.
5:2 inetd 0 [2345] /sbin/telnetd allow eth0:2323,eth2:2323,eth1:2323
6:1 inetd 0 [345] /sbin/dropbear allow eth0:222
6:2 inetd 0 [345] /sbin/dropbear allow *:22 deny eth0
```
Running
-------
@@ -378,7 +346,7 @@ LILO, U-Boot/Barebox or RedBoot) configuration to append the following
to the kernel command line:
```shell
init=/sbin/finit
append="init=/sbin/finit"
```
Remember to also set up an initial `/etc/finit.conf` before rebooting!
doc/signals.md
+41
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@@ -0,0 +1,41 @@
Finit Signals
=============
Finit is often used on embedded and small Linux systems with BusyBox.
Though Finit comes with its own tools for (poweroff, halt, reboot), for
compatibility with the existing BusyBox toolset the following signals
have been adopted:
* `SIGUSR1`
Same effect as `finit q`, reloads all *.conf files in `/etc/finit.d/`
* `SIGUSR1`
Calls shutdown hooks, including HOOK_SHUTDOWN, stops all running
processes, and unmounts all file systems. Then tells kernel to
halt. Most people these days want SIGUSR2 though.
SysV init and systemd use this to re-open their FIFO/D-Bus.
* `SIGUSR2`
Like SIGUSR1, but tell kernel to power-off the system, if ACPI
or similar exists to actually do this. If the kernel fails
power-off, Finit falls back to halt.
SysV init N/A, systemd dumps its internal state to log.
* `SIGTERM`
Like `SIGUSR1`, but tell kernel to reboot the system when done.
SysV init N/A, systemd rexecutes itself.
* `SIGINT`
Sent from kernel when the CTRL-ALT-DEL key combo is pressed.
SysV init and systemd default to reboot with `shutdown -r`.
Finit currently forwards this to `SIGTERM`.
* `SIGPWR`
Sent from a power daemon, like `powstatd(8)`, on changes to the
UPS status. Traditionally SysV init read /etc/powerstatus and
acted on "OK", "FAIL", or "LOW" and then removed the file.
Finit currently forwards this to `SIGUSR2`.
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