The easiest way is to start from an existing configuration file to bring down the memory usage, and then tune it to bring back adequate performance. On Debian/Ubuntu you might wish to replace your installed /etc/mysql/my.cnf with my-small.cnf that can be found in /usr/share/doc/my-server-5.0/examples. I am also attaching a my.cnf here that is taken out from CentOS 4 installation of LxAdmin (which has been famous for its low-memory foot print). It is pretty much based on my-small.cnf. Some important notes:

• skip-bdb and skip-innodb are added, so you don’t get BSD DB nor InnoDB support. BSD DB support in MySQL is pretty much obsolete, and many open source scripts don’t rely on the presence of InnoDB. A low end VPS is not likely to enjoy the concurrency InnoDB is offering anyway. Transaction and referential integrity? Real Programmers^TM write their own rollback routines :)

• key_buffer is only 16K which is far from enough. key_buffer is pretty much one of the most important parameter for MyISAM tables and I usually bump it up to at least 1MB. The same can be said about table_cache — 4 is way too small. A WordPress page will likely touch 10 tables, and much more for apps like Drupal or MediaWiki.

• Query cache might be a good thing if you intend to run a busy site on such a low end VPS (provided that it has small data set, mostly read, like blogs, news sites, etc). I have my query_cache_limit set to 256K and query_cache_size set to 4M here.

After a few adjustment you should be able to start mysqld at around 5-6MB RSS. You might need to check the runtime variables to monitor the performance and how everything works out.