What is Finit?

Background

• Alternative init, c.f., traditional UNIX System V init, or systemd
• Reverse engineered from the Asus EeePC fastinit by Claudio Matsuoka
• Finit v1 was very limited, idea was to limit then expensive fork+exec calls
  → get to X quickly!

/etc/finit.conf

task [S] /libexec/system/setup.sh  -- Bootstrap system

service [2345] foo -args           -- Foo service

service [2345] <pid/foo> bar -args -- Bar service
service [2345] <pid>bar> baz -args -- Baz service

tty [12345789] console
tty :1 [12345789] tty1
tty :2 [2345] tty2
tty :3 [2345] tty3

service [LVLS] <COND> log env:[-]/etc/default/daemon daemon ARGS -- Service daemon
^       ^      ^      ^   ^                          ^      ^       ^
|       |      |      |   |                          |      |        `---------- Optional description
|       |      |      |   |                          |       `------------------ Daemon arguments
|       |      |      |   |                           `------------------------- Path to daemon
|       |      |      |    `---------------------------------------------------- Optional env. file
|       |      |       `-------------------------------------------------------- Redirect output to log
|       |       `--------------------------------------------------------------- Optional conditions
|        `---------------------------------------------------------------------- Optional Runlevels
 `------------------------------------------------------------------------------ Monitored application

Changes in v4

initctl

initctl changes

• service identity same as in .conf file: job:id → name:id

    name:foo
    :id

• greatly improved output from

    initctl status
    initctl status foo

• improved interaction with user defined conditions

• new commands

new initctl commands

• Detailed status of services, with
• improved integration of service management, and
• custom usr/ conditions
• Also, spin-offs from the addition of cgroups support

initctl [status]               # Show status of all services (old)
initctl status foo             # Show status of service foo
initctl show foo               # show foo.conf
initctl edit [-c] foo          # edit (optionally create) foo.conf
initctl touch foo              # mark foo.conf as modified for reload
initctl cond [set,clear] bar   # user conditions, static & one-shot
initctl ps                     # tree view of known services with arguments
initctl top                    # top like view of services (cgroups)
initctl cgroup                 # cgroup view of services (limits)

cgroups v2

In-Depth

pre/post scripts

• Available for service stanzas

    service pre:/path/to/script.sh  foo -args -- Foo service
    service post:/path/to/script.sh bar -args -- Bar service

• Runs before services transition to READY state, conditions do the rest
• Runs after services have transitioned to STOPPING state, for cleanup task

• Default timeout for scripts: 3 sec, customize with general kill delay

    service post:/path/to/script.sh kill:9 baz -args -- Baz service

environment files

• /etc/default/foo or /etc/conf.d/foo

• Available for service stanzas

    service env:/etc/default/foo foo -n $FOO_ARGS -- Foo service

• Changes to /etc/default/foo are tracked as dependency to foo service
• Changes to environment files take effect after initctl reload

• Example:

    $ cat /etc/default/foo
    FOO_ARGS=”-args”

cgroups v2

• Global configuration of groups, standard cgrops v2 kernel syntax in /etc/finit.conf or /etc/finit.d/*.conf files.

    cgroup init   cpu.weight 100
    cgroup user   cpu.weight 100
    cgroup hej    cpu.weight 100
    cgroup system cpu.weight 9700

  For an overview, use initctl cgroup

• All run/task/services are by default placed in the system group
• Local getty are placed in the user group
  • Need PAM plugin to move PID of SSH and telnet users after login

tuning cgroups

• Per service selection of group, or for a set of tasks:

    cgroup.hej:mem.max:12345
    service [23] <pid/foo> bar -- Bar service
    service [23] <pid/foo> baz -- Baz service

• Per service tweaking of limits also possible:

    service [23] <pid/foo> cgroup.hej:mem.max:12345 frob -- Frob service

• Changes to cgroup configuration changes take effect after initctl reload

Demo

Fin

Join the discussion on GitHub or
#troglobit on Liberachat if IRC is more your thing.