Rooting N900 is much more simpler than any other phone available today. You just need rootsh to enable root access.

Here’s how to get rootsh:

• Go to Application manager>>Application catalogs>>New
• Write maemo.org extras-testing for catalog name
• Give web address as http://repository.maemo.org/extras-testing
• Enter fremantle as the distribution
• Enter free non-free for components

A simpler way would be to open this page on your N900 and click here. This link will automatically configure the repository for extras catalog.

Now simply download rootsh from Application Manager.

Once you are done with rootsh, open a terminal.

You can now either try sudo gainroot or rootsh. sudo gainroot gives us root access without enabling R&D mode while rootsh is much more effective if you want to run single commands.

If you are having problem with the sudo command, try downloading sudser from the extras catalog.

Warning : Root Access enables users to change the  file-system  and gives full access to all system files. DON’T play with it if you don’t know what you are doing.