finit/docs/TODO.md

Goals of Finit

The intent of finit is to monitor not just processes, but to supervise an entire system and the behavior of certain processes that declare themselves to be finit compliant. Similar to launchd, the goal of finit is to be a replacement for:

• init
• inetd
• crond
• watchdogd

A small and simple replacement, primarily for embedded systems, with a low dependency on external packages. A compliant software is one that can run as a damon in the foreground. If it can also touch its PID file after a reconfiguration (initctl reload), the Finit dependency system can also be used.

Near Future

• When a process dies, and Finit does not restart it, we should collect a siginfo_t from the SIGCHLD signal and supply to the user in case initctl status <process> is called to debug the issue.
• Merge UDP redirect service uredir as an UDP inetd variant
• Add finit.conf support for UPS notification (SIGPWR) to start a task using, e.g. <sys/power/{ok,fail,low}> conditions. More info in sig.c
• Add finit.conf support for ctrl-alt-delete (SIGINT) and kbrequest, i.e. KeyboardSignal, (SIGWINCH) behavior. Using conditions to a task, e.g, <sys/key/ctrlaltdel> and <sys/key/signal> like SIGPWR handling.
• Cron/At support, see below
• Write man pages for finit and finit.conf, steal from the excellent pimd man pages ...

General

• Add support for timed shutdown in Finit, including cancelled shutdown, possibly using an at-job, see crond section below

• Add support for JSON output, or similar, from initctl show, e.g. initctl show --json

• Solaris SMF (Service Management Facility) has some interesting features that may be well worth looking into adopting:

     svcs enable -rt svc:/network/ssh:default
  

  That is: (r)esolve dependencies and only enable ssh (t)emporary in the default runlevel when networking is available.

• initctl add /sbin/service -n -- Service description, for details see above Solaris SMF featuer, issue #55 and issue #69, https://github.com/troglobit/finit/issues/69#issuecomment-287907610

• Changing the name of a pidfile, pid:[/path/]file.pid, after a service has been started is not supported atm. The previous name will not be (never) removed and the new name will not be created until the process has been stopped and started again.

• PID files created in subdirectories to /run is not supported right now inotify listeners should be automatically created (and removed) when a subdirectory is added (or removed).

Init

Finit in itself is not SysV Init compatible, it doesn't use /etc/rc.d and /etc/inet.d scripts to boot the system. However, a plausible way to achieve compatibility would be to add a plugin to finit which reads /etc/inittab to be able to start standard Linux systems.

Inetd

• Add support for throttling connections.
• Optimize interface filtering by using socket filter. The functions inet_*_peek() and inetd_is_allowed() used for interace filtering should be possible to rewrite as socket filters.
• Optimize HTTP/HTTPS inetd connections by adding basic support for the inetd variant redir http/tcp@eth0 nowait [2345] 127.0.0.1:8080, which would reduce the overhead of spawn the web server on each HTTP connection, yet still provide a means of filtering access per iface.

Crond

Requirements are quite rudimentary, basic cron functionality, mainly system-level timed periodic tasks:

• Periodically run a task, in a matching runlevel
• Optionally run as non-root (crontab -e as operator)

Proposed syntax:

# Crontab
cron @SPEC [LVLS] /path/to/cmd [ARGS] -- Optional descr

# One-shot 'at' command
at @YY-mm-ddTHH:MM [LVLS] /path/to/cmd [ARGS] -- Optional descr

Notice the ISO date in the at notation. The cron @SPEC could use are mo loose notation, e.g. @hourly, @midnight, @daily, @weekly, @reboot, etc. The runlevels is extra filtering sugar. E.g., if cron service is only allowed in runlevels two or three it will not start if system currently is in runlevel four.

To run a command as another user the .conf file must have a that owner. E.g., /etc/finit.d/extra.conf may be owned by operator and only hold cron ... lines.

What would be extremely useful is if initctl, or a homegrown at, could support the basic functionality of the at command directly from the shell -- that way setting up one-time jobs would not entail re-reading /etc/finit.conf