Add signal watcher system with power cycle triggers (#28)

* Related: https://github.com/getumbrel/umbrel-manager/pull/21

* Related: https://github.com/getumbrel/umbrel-dashboard/pull/130

* Add signal watcher system with power cycle triggers

* Stop docker containers before system shutdown

* karen

* Run karen triggers async

* Allow specifying an event dir

* Check root_der exists

* Add space

* Check dependencies

* Make sure karen is run as root

* Make karen more kareny

* Mount signals dir from umbrel-manager on host

docker-compose.yml

@@ -85,6 +85,7 @@ services:
                 stop_grace_period: 5m30s
                 volumes:
                         - ${PWD}/db:/db
+                        - ${PWD}/events/signals:/signals
                         - /var/run/docker.sock:/var/run/docker.sock
                         - /usr/bin/docker:/usr/bin/docker
                         - ${PWD}:${PWD}

events/triggers/reboot

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+docker-compose stop
+shutdown -r now

events/triggers/shutdown

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+docker-compose stop
+shutdown -h now

karen

@@ -0,0 +1,53 @@
+#!/usr/bin/env bash
+
+# karen watches for signals and executes triggers in the events dir
+# karen gets triggered a lot
+
+check_dependencies () {
+  for cmd in "$@"; do
+    if ! command -v $cmd >/dev/null 2>&1; then
+      echo "This script requires \"${cmd}\" to be installed"
+      exit 1
+    fi
+  done
+}
+
+check_root () {
+  if [[ $UID != 0 ]]; then
+    echo "Error: This script must be run as root."
+    echo "Can I speak to a manager please?"
+    exit 1
+  fi
+}
+
+check_dependencies fswatch readlink dirname
+
+check_root
+
+if [[ -n "$1" ]]; then
+  root_dir="$(readlink -f $1)"
+else
+  root_dir="$(dirname $(readlink -f ${BASH_SOURCE[0]}))/events"
+fi
+signal_dir="$root_dir/signals"
+trigger_dir="$root_dir/triggers"
+
+if [[ ! -d "$root_dir" ]]; then
+  echo "Root dir does not exist '$root_dir'"
+  exit 1
+fi
+
+echo "karen is running in $root_dir"
+fswatch -0 --event=PlatformSpecific $signal_dir | while read -d "" event; do
+  signal="${event#"$signal_dir"}"
+  signal="${signal#"/"}"
+  trigger="$trigger_dir/$signal"
+
+  echo "Got signal: $signal"
+  if test -x "$trigger"; then
+    echo "karen is getting triggered!"
+    "$trigger" &
+  else
+    echo "No trigger found"
+  fi
+done