If ever a installation or upgrade to MySQL 5.1 goes wrong and you want to revert back to MySQL 5.0 by installing 5.0, you will probably run into the following nasty error message.
Unpacking mysql-server-5.0 (from …/mysql-server-5.0_5.0.51a-24+lenny5_amd64.deb) …
Aborting downgrade from (at least) 5.1 to 5.0.
dpkg: error processing /var/cache/apt/archives/mysql-server-5.0_5.0.51a-24+lenny5_amd64.deb (–unpack):
subprocess pre-installation script returned error exit status 1
Errors were encountered while processing:
E: Sub-process /usr/bin/dpkg returned an error code (1)
You probably get this error message when you run “sudo apt-get install mysql-server”. To fix this problem, simply run:
Warning: THIS WILL DELETE ALL YOUR DATA. Pleas backup your tables before continuing.
this will delete the mysql data directory, which will fix the issue! continue your downgrade back to 5.0 by running: