85 lines
2.5 KiB
Text
85 lines
2.5 KiB
Text
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cinit - braindumps - shutdown
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=============================
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Nico Schottelius <nico-cinit@@@@schottelius.org>
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v0.1, for cinit-0.3, 2007-01-11
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:Author Initials: NS
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Just some braindumps. Do not read.
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Introduction
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------------
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Shutting down the system.
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When?
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-----
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- reboot
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- halt
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- power off
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- further needed?
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How / What?
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------------
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- Stop services in the correct order
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* reuse the service tree / needs / needed_by!
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* call off, if existent
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* if respawning, send SIGTERM?
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- not if off is existent?
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* give some variables to off?
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- $RESPAWN_PID: if respawning
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- send SIGTERM to other apps?
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* or put that into special? special/post_svc_shutdown
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- call special/{halt,poweroff,reboot}
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* no, implemented that directly into cinit!
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- implement timely controlled shutdown:
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* cinit.shutdown forks (?) itself and waits, then sends a signal
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to cinit to initiate the shutdown process
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* create mappers for target OS
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- Linux
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- {free,net,open}bsd
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- others may contribute theirself
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- also implement poweroff
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* kill -TERM 1
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- also implement reboot
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* kill -HUP 1
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- also implement halt
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* kill -USR1 1
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The implementation
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-----------------
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x shutdown is initiated
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x disable communication (nobody can influence us anymore)
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x install special signal handler?
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- no. we do not care about zombies anymore, we are gone soon anyway
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- simply reset to the default
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- begin to shutdown services
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* where to start?
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* begin shutdown at the end of the tree, viewing/sorting it by the 'needed_by'
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-> where to begin sort?
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-> worst implementation: scan all services (easy for now)
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-> result: list of services, that noone needs :-)
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* stop those services and step above
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- stop a service, as soon as noone needs it anymore
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* check all needed_by links
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* more or less the inverted gen_svc_tree
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- how to shutdown a service
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* if existing, call off
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- if off does not exist:
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* if respawn: send sigterm to the process
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* also implement sigkill at this stage?
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- think we can delay it to the end
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- otherwise users can use off!
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- implement environment for off ($cinit_respawn_pid, $cinit_service_name)
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- do *NOT* care about the return value, we can't do anything for it
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anymore anyway
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- after all services are shutdown, kill all remaining services
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* SIGTERM
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* wait(defined_time_in_seconds)
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* SIGKILL
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- call the last command
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* to cleanup the system
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- umount -a (if needed)
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- swapoff (if needed)
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- sync (if needed)
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- switch off
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