www.nico.schottelius.org/software/cinit/browse_source/cinit-0.0.5/old/idea02

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/etc/cinit
   -> init/
   -> shutdown/
   -> reboot/

<service>
   needs/ -> we wait until all parallel processes are finished _and_ we
             don't start if one fails
   wants/ -> we start all of them parallel and wait for them?
   hold/
   wait -> wait until process finished
   run -> program to execute
   params -> \n seperated argument list
   respawn -> respawn it
   
services may only be under /etc/cinit?
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Service-Status: (see struct svc, cinit.h)

- abs_path
- status (respawn,tmp,once)
- pid 

abs_path\0status\0pid\0

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starting services:

run_svc("/etc/cinit/service/")
   -> exec run $params
Later:
   -> check if service already running  -> return OK
   -> check needs/ -> check wants/
      -> run_svc($cur)

   When run_svc returns, the service is started and all service it needs, too.

   
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   -> check needs/
      -> exists -> fork( run_run_svcs() ) and continue
         (fork) -> fork() run_svc(needs/*);
   -> check wants/
      -> exists -> run_svc(wants/*);
   -> waitfor(need_run_svc)
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run_run_svcs()
   -> start parallel (forked) run_svc() for every service
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main()
   - run_svc /etc/cinit/init/
   - sleep()? -> simply do nothing -> do we need to fork ourselves? No, we are init.
spaeter:
   - open /dev/console W_ONLY
   - make stdin == /etc/cinit/in
   - make stdout, stderr /dev/console

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eof

Things, which are clear

- we need to fork before execl(), as excel() replaces us.
- chdir() _after_ fork()


profiles support: profile=$profile

   start 
      "service.$profile" if exists, instead of
      "service"

starting services:

cinit:
   pipe()
   set_status_tmp()
   fork() --> failure --> clear_service
      cinit_process_watcher():
         fork()
            execve(process,args,env)
         waitpid() -> for once? PROCESS MUST RETURN!
         write_pipe()
   rmpipe()

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What to send over to cinit and read back?

   - first you need two pipes for every process: read+write (on both sides)
   - cinit wants
      o command
         - service temporary - trying to start in right now.
         - service executed once - fine
         - service executed once and that failed - :-(
         - service respawing
      o an identifier for the service (i from service list ;-)

   --> makes 2 bytes to read
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How cinit works:

cinit says: I want to start service xyz. (/etc/cinit/init on bootup)
cinit calls run_svc().
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int run_svc(char *relative_path):
   - check if service is already running or temporary (task list!)
      -> yes: return RT_PAR_OK
      -> no: continue.
   - set service to be temporary (ST_TMP) and retrieve SID (service ID)
   - walk through dependency tree and call run_svc
   - fork() -> so cinit can continue.
   - write cinit: check service, I want to start it 
      -> returns status of service (see ST_* in cinit.h)
   - cinit returns: ok, you are temporary
   - [that checked] check if service
      o is already started
      o is beeing started
   x check if rpath S_ISDIR
   x chdir(dir)
   - check needs - check wants
      - for every needs/* start run_svc
   - check respawn -> respawn = true
   - check run

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add_mod_svc(char *svc, int status)
   -> add or modify status of a service

   - check whether service exists, reset status
   - if not exists, insert if maximum of services is not reached
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cinit communications proto
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cinit:
   -> signal_handler on SIGCHLD
   run_init()
      -> run_svc(init)
         -> fork() -> do the work

signal_handler_child
   waitpid(.*)
      -> returns pid

   oder waitpid() in dem run_svc, wenn need/once?

   need:
      for i in need/*; do
         ( $service & );
      done
      wait(.*);

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cinit:

run_svc:
   checks what it needs (need/*)
   need/*
      fork()
         fork(), fork()

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Kommunikationsproblem:

   -> 1024 ist maximale anzahl offener sockets -> 510 von fifos,pipes
   - mehrere FIFOs?
   --> kommunikation gesichert, extrem viele fifos...
   --> etwas unsauber, aber geregelte kommunikation
   - mehrere PIPEs?
   --> viele PIPEs (HRHR)
   --> programme koennen nur von cinit gefork()ed werden.

   --> eine datei mit prozessen?
   --> einen RAM Bereich?
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cinit[1] <-> fifo <-> forker

forker?
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pfad vorher aufloesen?

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Kommunikation: ::Test::

   Test mit nur 2 FIFOs!

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sig_fifo()
read(..) als hauptaufgabe?