Fix `ghost start` not work

While trying to upgrade my Ghost blog to to latest version 3.15.1 last week, it always freezed at Starting Ghost step.

+ sudo systemctl is-active ghost_muyexi-im
✔ Ensuring user is not logged in as ghost user
✔ Checking if logged in user is directory owner
✔ Checking current folder permissions
+ sudo systemctl is-active ghost_muyexi-im
✔ Validating config
✔ Checking folder permissions
✔ Checking file permissions
✔ Checking content folder ownership
✔ Checking memory availability
✔ Checking binary dependencies
+ sudo systemctl start ghost_muyexi-im
☲ Starting Ghost: muyexi-im

From the log we can see ghost start is using systemctl to manage ghost service, use systemctl status ghost_muyexi-im we can see the sercie status:

● ghost_muyexi-im.service - Ghost systemd service for blog: muyexi-im
   Loaded: loaded (/var/www/ghost/system/files/ghost_muyexi-im.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2020-05-14 21:13:05 CST; 3min 2s ago
     Docs: https://docs.ghost.org
 Main PID: 25752 (ghost run)
    Tasks: 18 (limit: 1149)
   CGroup: /system.slice/ghost_muyexi-im.service
           ├─25752 ghost run
           └─25767 /usr/bin/nodejs current/index.js

The system node /usr/bin/nodejs is a version not supported by Ghost, and I'm using nvm for managing node versions, so I need to change the systemd service file at /var/www/ghost/system/files/ghost_muyexi-im.service.

[Unit]
Description=Ghost systemd service for blog: muyexi-im
Documentation=https://docs.ghost.org

[Service]
Type=simple
WorkingDirectory=/var/www/ghost
User=1000
Environment="NODE_ENV=production"
#ExecStart=/usr/bin/nodejs /usr/bin/ghost run
ExecStart=/usr/local/bin/node /usr/bin/ghost run // Switch to nvm node
Restart=always

[Install]
WantedBy=multi-user.target

After changed the node path, reload the service file:

systemctl daemon-reload

Now try ghost start, it should work again!