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116 lines
4.1 KiB
Markdown
116 lines
4.1 KiB
Markdown
Goals of Finit
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==============
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The intent of finit is to monitor not just processes, but to supervise
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an entire system and the behavior of certain processes that declare
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themselves to be finit compliant. Similar to launchd, the goal of
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finit is to be a replacement for:
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* init
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* inetd
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* crond
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* watchdogd
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A small and simple replacement, primarily for embedded systems, with a
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very low dependency on external packages.
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General
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-------
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* Add halt/poweroff/shutdown symlinks to finit and convert reboot, but
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only install symlinks if these tools don't already exist.
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* Add support for timed shutdown in Finit, including cancelled shutdown.
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* SysV init and systemd use SIGUSR1 to restart their FIFO/D-Bus. Add
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API restart to SIGHUP callback for the same functionality in Finit.
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* Add `finit.conf` support for UPS notification (SIGPWR) to start a task
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using, e.g. <sys/power/{ok,fail,low}> conditions. More info in sig.c
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* Add `finit.conf` support for ctrl-alt-delete (SIGINT) and kbrequest,
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i.e. KeyboardSignal, (SIGWINCH) behavior. Using conditions to a task,
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e.g, <sys/key/ctrlaltdel> and <sys/key/signal> like SIGPWR handling.
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* Add `IFF_RUNNING` support to netlink plugin along `IFF_IUP`
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* Allow process callbacks to be scripts.
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* Add support for a pipe/popen where we can listen for `STOP`, `START`
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and `RELOAD` on `STDOUT` from a script ... call it for example
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`.monitor=` in `svc_t` ... the script named as the basename of the
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service it monitors + `.sh`.
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* Implement `initctl stop|start|restart|reload|status <SVC>` and
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`service <SVC> stop|start|restart|reload|status` on top
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* Add support for JSON output, or similar, from `initctl show`, e.g.
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`initctl show --json`
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* Improve `initctl show SVC` output. Add service uptime, last ten SVC
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logs/history (historian), etc. Similar to `systemctl show SVC`
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* Add PRE and POST hooks for when switching between runlevels
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Init
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----
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Finit in itself is not SysV Init compatible, it doesn't use `/etc/rc.d`
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and `/etc/inet.d` scripts to boot the system. However, a plausible way
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to achieve compatibility would be to add a plugin to finit which reads
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`/etc/inittab` to be able to start standard Linux systems.
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Inetd
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-----
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* Add support for throttling connections.
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* Optimize interface filtering by using socket filter. The functions
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`inet_*_peek()` and `inetd_is_allowed()` used for interace filtering
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should be possible to rewrite as socket filters.
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* Optimize HTTP/HTTPS inetd connections by adding basic support for the
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`inetd` variant `redir http/tcp@eth0 nowait [2345] 127.0.0.1:8080`,
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which would reduce the overhead of spawn the web server on each HTTP
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connection, yet still provide a means of filtering access per iface.
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Crond
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-----
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Requirements are quite rudimentary, basic cron functionality, mainly
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system-level timed periodic tasks:
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* Periodically run a task, in a matching runlevel
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* Optionally run as non-root (`crontab -e` as operator)
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Proposed syntax:
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# Crontab
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cron @YY-mm-ddTHH:MM [LVLS] /path/to/cmd [ARGS] -- Optional descr
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# One-shot 'at' command
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at @YY-mm-ddTHH:MM [LVLS] /path/to/cmd [ARGS] -- Optional descr
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Notice the ISO date in notation. The runlevels is extra filtering
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sugar. E.g., if cron service is only allowed in runlevels two or three
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it will not start if system currently is in runlevel four.
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To run a command as another user the `.conf` file must have a that
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owner. E.g., `/etc/finit.d/extra.conf` may be owned by operator and
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only hold `cron ...` lines.
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What would be extremely useful is if `initctl`, or a homegrown `at`,
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could support the basic functionality of the `at` command directly from
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the shell -- that way setting up one-time jobs would not entail
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re-reading `/etc/finit.conf`
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Documentation
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-------------
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* Write man pages for finit and `finit.conf`, steal from the excellent
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`pimd` man pages ...
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* Add simple, *very* simple, `finit-simple.conf` example. To illustrate
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how close Finit3 still is to the original easy-to-use Finit0 :)
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[libwdt]: http://www.wehavemorefun.de/fritzbox/Libwdt.so
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[Fritz!Box source dump]: ftp://ftp.avm.de/fritz.box/fritzbox.fon_wlan_7170/x_misc/opensrc/
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