I ran into some problem upgrading from v13 in ubuntu 20.04 so, I decided to take backup with files and clean install new ubuntu 22.04 and installed v14 following this guide. There were no problems in installation of ERPN v14. But when I tried to restore the old database, this error appeared.
ERROR 2006 (HY000) at line 5828: Server has gone away
Table ‘tabDefaultValue’ missing in the restored site. Database not installed correctly, this can due to lack of permission, or that the database name exists. Check your mysql root password, validity of the backup file or use --force to reinstall
This gave Internal Server error in web browser.
Luckily I had taken backup of v14 before giving restore command. I restore and I have v14 up and running but I have yet to restore old data.
I had to do this to make the restore work. But the process went with a lot of errors most of which I didn’t understand. Nevertheless, managed to switch back to v13, restored backup and then again switched to v14. Now I have up and running ERPNext v14 with all my modifications/customizations and all files.