I followed the instructions here to upgrade to v4 on the same server.
I wanted to test it on one single site out of several installed, with this command:
However, the migration script ran on all sites and/or deleted EE3 (I didn’t quite follow everything that happened), but I could see that it attempted to run it on other sites on the server.
The script didn’t do anything according to what the guide said. It removed EE3 and didn’t migrate only one site. So when I tried to browse to one of the sites it was totally broken with only an NGINX error message.
Luckily I made a backup just before, so I could restore everything!
Just want to warn everyone to backup the server before migrating.
And please EE team, update the migration guide and recommend people to backup their sites before trying the migration script, even the dry run.