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finit/docs/config.md
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Joachim Nilsson decdc1560a Support for monitoring forking services/sysv daemons 
Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
2020-02-26 14:10:47 +01:00

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Configuration
=============
* [Introduction](#introduction)
* [Service Wrapper Scripts](#service-wrapper-scripts)
* [Syntax](#syntax)
* [Limitations](#limitations)
* [/etc/finit.conf](#etcfinitconf)
* [/etc/finit.d](#etcfinitd)
Introduction
------------
Finit can be configured using only the original `/etc/finit.conf` file
or in combination with `/etc/finit.d/*.conf`. Finit 3 can even start a
system using only `/etc/finit.d/*.conf`, highly useful for package-based
Linux distributions -- each package can provide its own "script" file.
- `/etc/finit.conf`: main configuration file
- `/etc/finit.d/*.conf`: snippets, usually one service per file
Not all configuration directives are available in `/etc/finit.d/*.conf`
and some directives are only available at bootstrap, runlevel `S`, see
the section [Limitations](#limitations) below for details.
To add a new service, simply drop a `.conf` file in `/etc/finit.d` and
run `initctl reload`. (It is also possible to `SIGHUP` to PID 1, or
call `finit q`, but that has been deprecated with the `initctl` tool).
Finit monitors all known active `.conf` files, so if you want to force
a restart of any service you can simply touch its corresponding `.conf`
file in `/etc/finit.d` and call `initctl reload`. Finit handle any
and all conditions and dependencies between services automatically.
It is also possible to drop `.conf` files in `/etc/finit.d/available/`
and use `initctl enable` to enable a service `.conf` file. This may be
useful in particular to Linux distributions that may want to install all
files for a package and let the user decide when to enable a service.
On `initctl reload` the following is checked for all services:
- If a service's `.conf` file has been removed, or its conditions are no
longer satisifed, the service is stopped.
- If the file is modified, or a service it depends on has been reloaded,
the service is reloaded (stopped and started).
- If a new service is added it is automatically started — respecting
runlevels and return values from any callbacks.
For more info on the different states of a service, see the separate
document [Finit Services](service.md).
Service Wrapper Scripts
-----------------------
If your service requires to run additional commands, executed before the
service is actually started, like the systemd `ExecStartPre`, you can
use a wrapper shell script to start your service.
The Finit service `.conf` file can be put into `/etc/finit.d/available`,
so you can control the service using `initctl`. Then use the path to
the wrapper script in the Finit `.conf` service stanza. The following
example employs a wrapper script in `/etc/start.d`.
**Example:**
* `/etc/finit.d/available/program.conf`:
```conf
service [235] <!> /etc/start.d/program -- Example Program
```
* `/etc/start.d/program:`
```shell
#!/bin/sh
# Prepare the command line options
OPTIONS="-u $(cat /etc/username)"
# Execute the program
exec /usr/bin/program $OPTIONS
```
**Note:**, that the example sets `<!>` to denote that it doesn't support
`SIGHUP`. That way Finit will stop/start such the service instead of
sending SIGHUP at restart/reload.
Syntax
------
* `host <NAME>`, or `hostname <NAME>`
Set system hostname to NAME, unless `/etc/hostname` exists in which
case the contents of that file is used.
* `module <MODULE> [ARGS]`
Load a kernel module, with optional arguments. Similar to `insmod`
command line tool.
Note, there is both a `modules-load.so` and a `modprobe.so` plugin
that can handle module loading better. The former supports loading
from `/etc/modules-load.d/`, and the latter uses kernel modinfo to
automatically load (or coldplug) every required module. For hotplug
we recommend the BusyBox mdev tool, add to `/etc/mdev.conf`:
$MODALIAS=.* root:root 0660 @modprobe -b "$MODALIAS"
* `network <PATH>`
Script or program to bring up networking, with optional arguments
* `rlimit [hard|soft] RESOURCE <LIMIT|unlimited>` Set the hard or soft
limit for a resource, or both if that argument is omitted. `RESOURCE`
is the lower-case `RLIMIT_` string constants from `setrlimit(2)`,
without the prefix. E.g. to set `RLIMIT_CPU`, use `cpu`.
LIMIT is an integer that depends on the resource being modified, see
the man page, or the kernel `/proc/PID/limits` file, for details.
Finit versions before v3.1 used `infinity` for `unlimited`, which is
still supported, albeit deprecated.
```shell
# No process is allowed more than 8MB of address space
rlimit hard as 8388608
# Core dumps may be arbitrarily large
rlimit soft core infinity
# CPU limit for all services, soft & hard = 10 sec
rlimit cpu 10
```
`rlimit` can be set globally, in `/etc/finit.conf`, or locally for
a set of task/run/services, in `/etc/finit.d/*.conf`.
* `runlevel <N>`
N is the runlevel number 1-9, where 6 is reserved for reboot.
Default is 2.
* `run [LVLS] <COND> /path/to/cmd ARGS -- Optional description`
One-shot command to run in sequence when entering a runlevel, with
optional arguments and description.
`run` commands are guaranteed to be completed before running the next
command. Highly useful if true serialization is needed.
* `task [LVLS] <COND> /path/to/cmd ARGS -- Optional description`
One-shot like 'run', but starts in parallel with the next command.
Both `run` and `task` commands are run in a shell, so pipes and
redirects can be freely used:
```shell
task [s] echo "foo" | cat >/tmp/bar
```
* `sysv [LVLS] <COND> /path/to/init-script -- Optional description`__
Similar to `task` is the `sysv` stanza, which can be used to call SysV
style scripts. The primary intention for this command is to be able to
re-use much of existing setup and init scripts in Linux distributions.
When entering an allowed runlevel, Finit calls `init-script start`,
when entering a disallowed runlevel, Finit calls `init-script stop`,
and if the Finit .conf, where `sysv` stanza is declared, is modified,
Finit calls `init-script restart` on `initctl reload`. Similar to
how `service` stanzas work.
Forking services started with `sysv` scripts can be monitored by Finit
by declaring the PID file to look for: `pid:!/path/to/pidfile.pid`.
* `service [LVLS] <COND> /path/to/daemon ARGS -- Optional description`
Service, or daemon, to be monitored and automatically restarted if it
exits prematurely.
For daemons that support it, we recommend appending `--foreground`, or
`--no-background`, argument to prevent them from forking off a
sub-process in the background. This is the most reliable way to
monitor a service.
However, not all daemons support running in the foreground, or they
may start logging to the foreground as well, these are called forking
services and are supported using the same syntax as forking `sysv`
services, using the `pid:!/path/to/pidfile.pid` syntax.
In the case of `ospfd` (below), we omit the `-d` flag to prevent it
from forking (daemonizing):
```shell
service [2345] <svc/sbin/zebra> /sbin/ospfd -- OSPF daemon
```
The `[2345]` is the runlevels `ospfd` is allowed to run in, they are
optional and default to level 2-5 if left out.
The `<...>` is the condition for starting `ospfd`. In this example
Finit waits for another service, `/sbin/zebra`, to have created its
PID file in `/var/run/zebra.pid` before starting `ospfd`.
Some services do not maintain a PID file and rather than patching each
application Finit provides a workaround. A `pid` keyword can be set
to have Finit automatically create (when starting) and later remove
(when stopping) the PID file. The file is created in the `/var/run`
directory using the `basename(1)` of the service. The default can be
modified with an optional argument:
pid[:[/path/to/]filename[.pid]]
For example, by adding `pid:/run/foo.pid` to the service `bar` that
PID file will, not only be created and removed automatically, but also
be used by the Finit condition subsystem. So another service/run/task
can depend on `<svc/foo>`.
If a service `bar` *does* maintain a PID file, but using `foo.pid`, we
can inform Finit of this by prepending an `!` to the argument.
pid:!/run/foo.pid
Here Finit will *not* create/remove/touch the PID file, only use it
for the condition handling instead of the default PID file name.
For a detailed description of conditions, and how to debug them, see
the [Finit Conditions](conditions.md) document.
If a service should not be automatically started, it can be configured
as manual with the optional `manual` argument. The service can then be
started at any time by running `initctl start <service>`.
manual:yes
The name of a service, shown by the `initctl` tool, defaults to the
basename of the service executable. It can be changed with the
optional `name` argument:
name:<service-name>
* `inetd service/proto[@iflist] <wait|nowait> [LVLS] /path/to/daemon args`
Launch a daemon when a client initiates a connection on an Internet
port. Available services are listed in the UNIX `/etc/services` file.
Finit can filter access to from a list of interfaces, `@iflist`, per
inetd service as well as listen to custom ports.
```shell
inetd ftp/tcp nowait @root /usr/sbin/uftpd -i -f
inetd tftp/udp wait @root /usr/sbin/uftpd -i -t
```
The following example listens to port 2323 for telnet connections and
only allows clients connecting from `eth0`:
```shell
inetd 2323/tcp@eth0 nowait [2345] /sbin/telnetd -i -F
```
The interface list, `@iflist`, is of the format `@iface,!iface,iface`,
where a single `!` means to deny access. Notice how interfaces are
comma separated with no spaces.
The `inetd` directive can also have ` -- Optional Description`, only
Finit does not output this text on the console when launching inetd
services. Instead this text is sent to syslog and also shown by the
`initctl` tool. More on inetd below.
* `runparts <DIR>`
Call [run-parts(8)][] on `DIR` to run start scripts. All executable
files, or scripts, in the directory are called, in alphabetic order.
The scripts in this directory are executed at the very end of runlevel
`S`, bootstrap.
It can be beneficial to use `S01name`, `S02othername`, etc. if there
is a dependency order between the scripts. Symlinks to existing
daemons can talso be used, but make sure they daemonize by default.
Similar to the `/etc/rc.local` shell script, make sure that all your
services and programs either terminate or start in the background or
you will block Finit.
* `include <CONF>`
Include another configuration file. Absolute path required.
* `log size:200k count:5`
Log rotation for run/task/services using the `log` sub-option with
redirection to a log file. Global setting, applies to all services.
The size can be given as bytes, without a specifier, or in `k`, `M`,
or `G`, e.g. `size:10M`, or `size:3G`. A value of `size:0` disables
log rotation. The default is `200k`.
The count value is recommended to be between 1-5, with a default 5.
Setting count to 0 means the logfile will be truncated when the MAX
size limit is reached.
* `tty [LVLS] <DEV> [BAUD] [noclear] [nowait] [nologin] [TERM]`
`tty [LVLS] <CMD> <ARGS> [noclear] [nowait]`
The first variant of this option uses the built-in getty on the given
TTY device DEV, in the given runlevels. The DEV may be the special
keyword `@console`, which is very useful on embedded systems. Default
baud rate is `38400`.
**Example:**
```conf
tty [12345] /dev/ttyAMA0 115200 noclear vt220
```
The second `tty` syntax variant is for using an external getty, like
agetty or the BusyBox getty.
By default both variants *clear* the TTY and *wait* for the user to
press enter before starting getty.
**Example:**
```conf
tty [12345] /sbin/getty -L 115200 /dev/ttyAMA0 vt100
tty [12345] /sbin/agetty -L ttyAMA0 115200 vt100 nowait
```
The `noclear` option disables clearing the TTY after each session.
Clearing the TTY when a user logs out is usually preferable.
The `nowait` option disables the `press Enter to activate console`
message before actually starting the getty program. On small and
embedded systems running multiple unused getty wastes both memory
and CPU cycles, so `wait` is the preferred default.
The `nologin` option disables getty and `/bin/login`, and gives the
user a root (login) shell on the given TTY `<DEV>` immediately.
Needless to say, this is a rather insecure option, but can be very
useful for developer builds, during board bringup, or similar.
Notice the ordering, the `TERM` option to the built-in getty must be
the last argument.
Embedded systems may want to enable automatic `DEV` by supplying the
special `@console` device. This works regardless weather the system
uses `ttyS0`, `ttyAMA0`, `ttyMXC0`, or anything else. Finit figures
it out by querying sysfs: `/sys/class/tty/console/active`.
**Example:**
```conf
tty [12345] @console 115200 noclear vt220
```
On really bare bones systems Finit offers a fallback shell, which
should not be enabled on production systems since. This because it
may give a user root access without having to log in. However, for
bringup and system debugging it can come in handy:
```shell
configure --enable-fallback-shell
```
One can also use the `service` stanza to start a stand-alone shell:
```conf
service [12345] /bin/sh -l
```
When running <kbd>make install</kbd> no default `/etc/finit.conf` will
be installed since system requirements differ too much. Try out the
Debian 6.0 example `/usr/share/doc/finit/finit.conf` configuration that
is capable of service monitoring SSH, sysklogd, gdm and getty!
Every `run`, `task`, `service`, or `inetd` can also list the privileges
the `/path/to/cmd` should be executed with. Simply prefix the path with
`[@USR[:GRP]]` like this:
```shell
run [2345] @joe:users /usr/bin/logger "Hello world"
```
For multiple instances of the same command, e.g. a DHCP client or
multiple web servers, add `:ID` somewhere between the `run`, `task`,
`service` keyword and the command, like this:
```shell
service :1 [2345] /sbin/httpd -f -h /http -p 80 -- Web server
service :2 [2345] /sbin/httpd -f -h /http -p 8080 -- Old web server
```
Without the `:ID` to the service the latter will overwrite the former
and only the old web server would be started and supervised.
The `run`, `task`, `service`, or `inetd` stanzas also allow the keyword
`log` to redirect `stderr` and `stdout` of the application to a file or
syslog using the native `logit` tool. The full syntax is:
log:/path/to/file
log:prio:facility.level,tag:ident
log:console
log:null
log
Default `prio` is `daemon.info` and default `tag` is the basename of the
service or run/task command.
Log rotation is controlled using the global `log` setting.
**Example:**
service log:prio:user.warn,tag:ntpd /sbin/ntpd pool.ntp.org -- NTP daemon
Worth noting is that conditions is allowed for all these stanzas. For a
detailed description, see the [Conditions](conditions.md) document.
Limitations
-----------
To understand the limitations of `finit.conf` vs `finit.d` it is useful
to picture the different phases of the system: bootstrap, runtime, and
shutdown.
### /etc/finit.conf
This file used to be the only way to set up and boot a Finit system.
Today it is mainly used for pre-runtime settings like system hostname,
network bringup and shutdown:
- `host`, only at bootstrap, (runlevel `S`)
- `mknod`, only at bootstrap
- `network`, only at bootstrap
- `runparts`, only at bootstrap
- `include`
- `log`, global setting
- `shutdown`
- `runlevel`, only at bootstrap
- ... and all configuration stanzas from `/etc/finit.d` below
### /etc/finit.d
Support for per-service `.conf` files in `/etc/finit.d` was added in
v3.0 to handle changes of the system configuration at runtime. As of
v3.1 `finit.conf` is also handled at runtime, except of course for any
stanza that only runs at bootstrap. However, a `/etc/finit.d/*.conf`
does *not support* the above `finit.conf` settings described above, only
the following:
- `module`, but only at bootstrap
- `service`
- `task`
- `run`
- `inetd`
- `rlimit`
- `tty`
**NOTE:** The `/etc/finit.d` directory was previously the default Finit
`runparts` directory. Finit no longer has a default `runparts`, make
sure to update your setup, or the finit configuration, accordingly.
[run-parts(8)]: http://manpages.debian.org/cgi-bin/man.cgi?query=run-parts
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