by I was trialling a MySQL database upgrade today (from 5.0 to 5.1) and hit a nasty little gotcha that I feel warrants a mention (mostly to myself). In its simplest form, the upgrade process is very straightforward and involves simply loading data dumped from MySQL 5.0 into a 5.1 database (using a regular mysql command), followed by a once-off execution of the mysql_upgrade command (to bring the various tables and grants up to date):
$ mysql -u root -p testdb < dumped50.sql
$ mysql_upgrade -u root -p testdb
However, when I tried the latter command, I received this error:
Looking for 'mysql' in: mysql
FATAL ERROR: Can't find 'mysql'
I did fine a simple solution here which was to first change to the directory containing the mysql_upgrade program itself and execute it from there:
$ cd /opt/coolstack/mysql/bin
$ ./mysql_upgrade -u root -p testdb
As I said, its a simple solution and I do tend to follow this general rule most of the time but nevertheless, the error generated when you don’t do this is far for informative.