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Code around sleep was written into the service manager's sleep units by the module that needed it, and the mesh could not tell a sleeping machine from a lost one. power runs every module's code for the six moments, each piece bounded, owns logind's power handling from its settings, and says booted, sleeping, woke, shutting-down and the power source on the bus, sleeping under logind's delay lock before the machine sleeps.
power
A machine's power (novox/hq ADR 0211). This module holds node-power on every machine, servers
included, because every machine boots and shuts down. It owns logind's power key and lid handling. It
runs the code other modules contribute for the power moments, and it publishes the machine's power
states on the bus.
What it owns
/etc/systemd/logind.conf.d/power.conf |
the power key and the lid, from this module's settings (below); logind is reloaded, never restarted |
/etc/mesh-power/moments/<moment> |
for each moment, every module's code as the controller placed it (${shell:<moment>:<slot>}) |
/usr/local/lib/mesh-power/bin/power-moment |
the runner: each module's piece on its own, as root, with sh, bounded (MESH_POWER_BOUND, default 30 s); every outcome in the journal under mesh-power |
| five units | mesh-power-after-boot, -before-shutdown (its stop is the shutdown, while the network is still up), -before-sleep, -after-wake, -supply |
/etc/udev/rules.d/90-mesh-power.rules |
a power supply's change starts mesh-power-supply, which runs on-mains or on-battery once per change of source |
The moments, and how a module adds code
The moments are after-boot, before-sleep, after-wake, before-shutdown, on-mains and
on-battery. A module declares a shell entry whose for names the moment, in the first,
normal or last slot, with POSIX shell code. That entry depends on this seat (ADR 0210). The code
runs as root. Code that needs the operator's session finds it itself, as the laptop module's touchpad
reset does with runuser.
One rule for contributed code: the runner splits the placed file at lines of the form # <module>,
which the controller writes before each module's piece. A comment line of the piece's own that is
one lowercase word would split it too, so comments in contributed code use more than one word.
Code that must run inside the sleep transaction, such as the NVIDIA driver's own suspend and resume units, is not a contribution. Its module keeps its own drop-ins on the sleep services (ADR 0211, "What got harder").
Settings
handle-power-key, handle-lid-switch, handle-lid-switch-external-power and
handle-lid-switch-docked, each one of logind's actions. They have no defaults, so the mesh's layer
must be set before the first assignment. The mesh's layer carries logind's own defaults (poweroff,
suspend, suspend, ignore). A machine's layer changes them: the laptop suspends on all four.
Events
| event | when |
|---|---|
booted |
once per boot, not per restart of the runtime (the boot id is remembered) |
sleeping |
before the machine sleeps: the module's watcher holds logind's delay lock, publishes, waits for the bus at most 3 s, and lets go |
woke |
after waking, queued until the bus is reachable |
shutting-down |
before a shutdown, as sleeping |
on-mains, on-battery |
when the power source changes, on a machine with a Mains supply |
battery-low |
at 10 % on battery, once per discharge |
Each carries the time it happened. Events the bus did not take wait in order and go out when it answers
again. A machine that said sleeping is asleep, not out of touch.
Tools
| tool | |
|---|---|
power_state |
boot time, source and battery, lid, logind's settings, and the watcher's lock, last sleep and wake, and queue |
power_hooks |
every moment's contributed pieces, with their module |
power_history |
boots, sleeps, wakes and moment runs from the journal |
power_run |
run one moment now, to test it (needs sudo -n) |
power_check |
units, runner, moment files, one logind writer, no hand-placed sleep hooks, the lock held, nothing stuck before the bus |
Migration
- The laptop: its model module owned
logind.conf.d/power.confand a touchpad resume unit. Both move here: the file to this module, and the resume to anafter-wakecontribution. - The desktop: the predecessor left
logind.conf.d/brightness.confand/etc/systemd/system-sleep/xinput-reset-touchpad.sh. Move both aside after the first push;power_checknames them while they remain. - The servers have no logind drop-ins and no sleep hooks today.
The lesson from the day this module was written belongs to the dbus module: a full upgrade restarted the system bus live on a workstation, and logins hung until a reboot.