When updating MySQL, you must take into account which version you're updating from, and which version you're updating to.
- From MySQL 4.0.x, to 4.1.x or newer, the crypted password format changes. If you're upgrading from 4.0.x then you'll either need to reset all password after the update, or else add "old_passwords" to the [mysqld] section of your /etc/my.cnf
- Before doing any updates of MySQL be sure to have create full backups of all databases.
If you're using CustomBuild, the update process is quite simple:
Edit the options.conf file, and set:
#Possible values - 5.0, 5.1, 5.5 mysql=5.1 mysql_inst=yes mysql_backup=yes
Save/exit, then type:
If you're going to do it manually (only if required), the bottom portion of this guide provides some information on that: