This is part of my mini Ghost series, where I document the problems I ran into during the migration and how I solved them. You can find the other posts at the bottom.
While I was messing around with my ghost upgrade, I encountered a strange error and I couldn't seem to find a solution for it online.
Message: Cannot read property 'engine' of undefined
In case you are just looking for the solution, here it is: The theme is probably missing and ghost can’t load your theme. If you want to know how I got myself into this situation, you can stick around for a bit more.
This problem came about when I was moving my ghost blog from my production development environment to the development environment to develop my theme. In order to have my posts locally, I simply copied the database file from the server to my local machine. (I use SQLite, that’s why the database is a file). Since my local theme folder name was different from the one on the server, ghost crashed when trying to start. The strange thing is that ghost doctor runs fine. So I presume they never thought people would change or rename their theme folder.
Another solution
Another method is to edit the database directly. In the ghost settings table, there is a field called theme. Set that field to casper, which is the default ghost theme and you should be able to start ghost again.
I hope this helps someone.
Appendix
I have added the full output below in case anyone needs it for debugging purposes.
jiaxun@jjjx-personal % ghost start
+ sudo systemctl is-active ghost_chaijiaxun-com
✔ 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_chaijiaxun-com
✔ Validating config
✔ Checking folder permissions
✔ Checking file permissions
✔ Checking content folder ownership
✔ Checking memory availability
+ sudo systemctl start ghost_chaijiaxun-com
+ sudo systemctl stop ghost_chaijiaxun-com
✖ Starting Ghost
A GhostError occurred.
Message: Cannot read property 'engine' of undefined
Suggestion: journalctl -u ghost_chaijiaxun-com -n 50
Debug Information:
OS: Ubuntu, v16.04
Node Version: v8.15.0
Ghost-CLI Version: 1.9.9
Environment: production
Command: 'ghost start'
Additional log info available in: /home/jiaxun/.ghost/logs/ghost-cli-debug-2019-01-16T07_10_35_928Z.log
Try running ghost doctor to check your system for known issues.
You can always refer to https://docs.ghost.org/api/ghost-cli/ for troubleshooting.