forked from synit/synit
94 lines
2.4 KiB
Markdown
94 lines
2.4 KiB
Markdown
---
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title: 'System control commands'
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---
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## systemctl
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Commands generally accept patterns to select subsets of the set of all
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units.
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- list-units
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- list-sockets
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- list-timers
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- is-active (predicate over units)
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- is-failed
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- status
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- show
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- cat (introspection on source files for units)
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- help (this is interesting!)
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- list-dependencies
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- start
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- stop
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- reload ("please reload your configuration" - even though we are
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mostly reactive, most services won't be, and sometimes config in
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files exists etc)
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- restart (stop (if running) and then start (unconditionally))
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- try-restart (if running, stop and then start)
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- reload-or-restart, try-reload-or-restart
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- isolate (effectively set a new "supergoal", removing all others. nb `AllowIsolate` flag)
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- kill
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- clean (remove various cache/state/config/log data)
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- freeze, thaw
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- set-property (for us, change a config .pr file; no --runtime equivalent, though)
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- reset-failed (resets the state variables of the supervisor)
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- (several others)
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Enable vs start.
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Enable: `--system`, `--user`, `--runtime`, `--global`: various scopes for enabling a unit.
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Container management.
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Job management. (It has a job queue!)
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Environment management for spawned services.
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`daemon-reexec`, serializes state for an upgrade
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System lifecycle: startup -> running -> (shutdown | (maintenance -?-> running))
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At shutdown or sleep, "inhibitor locks" exist. The action can respect
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or ignore these. Interactive shutdown/sleep requests default to
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respecting; non-interactive, to ignoring.
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`isolate` targets:
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- default
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- rescue
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- emergency
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- halt
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- poweroff
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- reboot
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- suspend
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- hibernate
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- hybrid-sleep
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- suspend-then-hibernate
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`switch-root`
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## Service unit configuration
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https://www.freedesktop.org/software/systemd/man/systemd.service.html
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Service templates: can take a single argument to become instantiated.
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If a service unit config file doesn't exist, falls back to looking for
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an init script and synthesizes a unit on the fly.
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Default dependencies:
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- requires sysinit.target
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- starts after sysinit.target
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- starts after basic.target
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- conflicts with shutdown.target
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- shuts down before shutdown.target (?)
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"slice units"? Oh ok, hierarchical supervision... and configuration of
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whole branches of the tree.
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Service lifecycle:
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- states: active, activating, deactivating, dead, inactive, starting, ... more?
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Options:
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- Type (it's complicated)
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