finit/docs

Configuration

• Introduction
• Service Wrapper Scripts
• Syntax
• Limitations
  • /etc/finit.conf
  • /etc/finit.d

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 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 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:

service [235] <!> /etc/start.d/program -- Example Program

• /etc/start.d/program:

#!/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.

        # 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:

        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):

        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 /sbin/bar that PID file will, not only be created and removed automatically, but also be used by the Finit condition subsystem. So a service/run/task can depend on <svc/sbin/foo>, notice the composition of conditions.

However, if a service bar does create a PID file, using foo.pid, we can inform Finit of this by prepending an !:

    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 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>

When stopping a service (run/task/sysv/service), either manually or when moving to another runlevel, Finit starts by sending SIGTERM, to allow the process to shut down gracefully. If the process has not been collected within 3 seconds, Finit sends SIGKILL. To halt the process using a different signal, use the option halt:SIGNAL, e.g., halt:SIGPWR. To change the delay between your halt signal and KILL, use the option kill:SEC, e.g., kill:10 to wait 10 seconds before sending SIGKILL.

• 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.

        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:

        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, or console, useful on embedded systems.

  The default baud rate is 0, i.e., keep kernel default.

  Example:

        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:

        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. The speed can be omitted to keep the kernel default.

Example:

        tty [12345] @console 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:

        configure --enable-fallback-shell

One can also use the service stanza to start a stand-alone shell:

        service [12345] /bin/sh -l

When running make install 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:

    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:

    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 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.