There are many posts on this and they all have different solutions none of which I wanted to do because of the extent of packages that needed to be removed and reinstalled.
Most of these posts have the same initial observations. The user is getting 503/502 errors after an upgrade to Ghost v4 and they don't know why. They can run
ghost run at the command line and it works fine but when they run
ghost start they get these errors. Some users found upgrading the size of their VM's fixed the problem, others removed and reinstalled node and ghost. When looking at my systemd configuration I noticed a difference in where the ghost command and node commands were being ran from. When I ran at the command line they were out of
/usr/local/bin/node where as when they were ran by systemd they were being ran from
/usr/bin/node ... modifying the systemd configuration file located in
/lib/systemd/system/ghost_<url> and changing the
ExecStart line to look like below.
[Unit] Description=Ghost systemd service for blog: <blog url> Documentation=https://ghost.org/docs/ [Service] Type=simple WorkingDirectory=/var/ww/ghost User=999 Environment="NODE_ENV=production" ExecStart=/usr/local/bin/node /usr/local/bin/ghost run Restart=always [Install] WantedBy=multi-user.target
Once this is done execute
sudo systemctl daemon-reload followed by
ghost start once this was done the site was back up and running without any issues.