Slackアプリで作った自作ラズパイゼロ定点カメラをSystemdデーモンで自動起動するやり方

            + Linux系OSの起動直後に走る主要な起動プロセスの一つ
+ Systemd自身のプロセスIDはinitプロセスと呼ばれ、
    常に1(PID=1)で実行状態になる
+ 登録しておいた複数のアプリケーションを
    子プロセス(ユニットプロセス)として起動することができる
        

            #!/bin/bash

export SLACK_BOT_TOKEN=xoxb-xxxxxxx-xxxxxxx-xxxxxxxxxxxxx
export SLACK_APP_TOKEN=xapp-x-xxxxxxxx-xxxxxxxx-xxxxxxxxxxxxxxx

WORK_DIR=[index.jsが存在するフォルダまでの絶対パス]

node $WORK_DIR/index.js
        

            $ ls -la /etc/systemd/system
-rw-r--r--  1 root root 1552 Jul 20  2021 autologin@.service
drwxr-xr-x  2 root root 4096 May  7  2021 bluetooth.target.wants
lrwxrwxrwx  1 root root   42 May  7  2021 dbus-fi.w1.wpa_supplicant1.service -> /lib/systemd/system/wpa_supplicant.service
lrwxrwxrwx  1 root root   37 May  7  2021 dbus-org.bluez.service -> /lib/systemd/system/bluetooth.service
lrwxrwxrwx  1 root root   40 May  7  2021 dbus-org.freedesktop.Avahi.service -> /lib/systemd/system/avahi-daemon.service
lrwxrwxrwx  1 root root   45 May  7  2021 dbus-org.freedesktop.timesync1.service -> /lib/systemd/system/systemd-timesyncd.service
lrwxrwxrwx  1 root root   34 May  7  2021 dhcpcd5.service -> /lib/systemd/system/dhcpcd.service
drwxr-xr-x  2 root root 4096 May  7  2021 dhcpcd.service.d
drwxr-xr-x  2 root root 4096 May  7  2021 getty.target.wants
drwxr-xr-x  2 root root 4096 May  7  2021 getty@tty1.service.d
drwxr-xr-x  2 root root 4096 May  7  2021 halt.target.wants
drwxr-xr-x  2 root root 4096 Mar  3 02:09 multi-user.target.wants
drwxr-xr-x  2 root root 4096 May  7  2021 network-online.target.wants
drwxr-xr-x  2 root root 4096 May  7  2021 poweroff.target.wants
drwxr-xr-x  2 root root 4096 May  7  2021 rc-local.service.d
drwxr-xr-x  2 root root 4096 May  7  2021 reboot.target.wants
drwxr-xr-x  2 root root 4096 May  7  2021 remote-fs.target.wants
drwxr-xr-x  2 root root 4096 Feb  6 05:23 sockets.target.wants
lrwxrwxrwx  1 root root   31 Jul 20  2021 sshd.service -> /lib/systemd/system/ssh.service
drwxr-xr-x  2 root root 4096 May  7  2021 sysinit.target.wants
lrwxrwxrwx  1 root root   35 May  7  2021 syslog.service -> /lib/systemd/system/rsyslog.service
drwxr-xr-x  2 root root 4096 May  7  2021 timers.target.wants
        

            [Unit]
Description=Slack Remoted Camera Service
After=network-online.target local-fs.target
ConditionPathExists=/root

[Service]
Type=simple
User=root
Group=root
Restart=no
ExecStart=[ラッパースクリプトが存在するフォルダまでの絶対パス]/start-slack-app.sh

[Install]
WantedBy=multi-user.target
        

            $ sudo mv slack-cam.service /etc/systemd/system/
$ sudo chown root:root /etc/systemd/system/slack-cam.service
$ sudo chmod 644 /etc/systemd/system/slack-cam.service
$ ls -la /etc/systemd/system/ | grep slack-cam
-rw-r--r--  1 root root  482 Mar  3 02:48 slack-cam.service
        

            $ sudo systemctl daemon-reload
        

            $ sudo systemctl start slack-cam
        

            $ systemctl status slack-cam
● slack-cam.service - Slack Remoted Camera Service
   Loaded: loaded (/etc/systemd/system/slack-cam.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2022-03-03 03:07:09 GMT; 24h ago
 Main PID: 426 (start-slack-app)
    Tasks: 12 (limit: 725)
   CGroup: /system.slice/slack-cam.service
           ├─426 /bin/bash /*****************/start-slack-cam.sh
           └─430 node /*****************/index.js

Mar 03 03:07:46 raspberrypi start-slack-app.sh[426]: ⚡️ Bolt app is running!
        

            $ sudo systemctl enable slack-cam
        

            $ sudo systemctl disable slack-cam