I've done some searching, and have a good idea how to go about this, but unsure about the database. I've tried copying across the old database's files from /var/lib/mysql/dbispconfig (with mysql stopped) and now, I get an "error username or password empty" message. ISPconfig web console also takes time to load, so I guess I've missed something or done it wrong. Is there a recommended procedure to retrieve the DB from the files?
OK, I've found my error: I had also renamed/moved the new mysql database directory and replaced it with the one from the old server which I shouldn't have done. I have now restored ONLY the dbispconfig directory, updated the file permissions, and it seems to be working OK.
