I am new to DBA role, and wanted to know if there was any commands (or free software) that come with Mysql 5.5 (master/slave/slave) replication to quickly get familiar with the database, and also making sure my.cnf is set up with the correct parameters.
It will tell you stuff like what the major config params are set to, what technologies ara available in your server, take a 10 second status sample, analyze your schema etc.
Also worth to run pt-duplicate-key-checker at least once, to detect redundant keys.
I'm authoring the common_schema tool for MySQL, which also offers some diagnostics: the redundant_keys view is parallel to pt-duplicate-key-checker; the data_size_per_schema view will tell you, well, the datasize per schema; the auto_increment_columns view will tell you about "free space" in your AUTO_INCREMENT columns; and more.
Watching the processes as they go, using