Debian系统下Docker服务无法通过systemctl启动的修复求助

Looks like your docker.service file got corrupted during the VM crash—right now it only has the environment variable line, missing all the required systemd service sections that tell systemd how to start/stop Docker. That's exactly why you're seeing those "Assignment outside of section" and "lacks ExecStart/ExecStop" errors.

Here's how to fix it step by step:

1. Backup the broken file first (just in case):

   sudo cp /lib/systemd/system/docker.service /lib/systemd/system/docker.service.bak
   

2. Replace the corrupted service file with a valid one
   Open the file with your favorite editor (I'll use nano here for simplicity):

   sudo nano /lib/systemd/system/docker.service
   

   Paste the following content (this matches the default Docker service config for Debian 9, plus your existing environment variable):

   [Unit]
   Description=Docker Application Container Engine
   Documentation=https://docs.docker.com
   After=network-online.target firewalld.service containerd.service
   Wants=network-online.target
   Requires=containerd.service
   
   [Service]
   Type=notify
   ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
   ExecReload=/bin/kill -s HUP $MAINPID
   TimeoutSec=0
   RestartSec=2
   Restart=always
   StartLimitBurst=3
   StartLimitInterval=60s
   LimitNOFILE=infinity
   LimitNPROC=infinity
   LimitCORE=infinity
   TasksMax=infinity
   Delegate=yes
   KillMode=process
   Environment="GOOGLE_APPLICATION_CREDENTIALS=/etc/docker/key.json"
   
   [Install]
   WantedBy=multi-user.target
   

   Save and exit: press Ctrl+O, hit Enter, then Ctrl+X.

3. Reload systemd and restart Docker
   Tell systemd to pick up the new service config:

   sudo systemctl daemon-reload
   

   Now start Docker via systemctl:

   sudo systemctl start docker
   

4. Verify everything works
   Check the service status to confirm it's running:

   sudo systemctl status docker
   

   If you want Docker to start automatically on boot, run:

   sudo systemctl enable docker
   

This restores the full, valid systemd service structure while keeping your GOOGLE_APPLICATION_CREDENTIALS environment variable—systemd will now know exactly how to manage the Docker service again.

内容的提问来源于stack exchange，提问作者DarkLeafyGreen