Type root to gain root access. Be careful while deleting/changing stuff as you would brick your lovely N900 

To delete a file type rm filename

To delete an empty folder type rm foldername 

To delete folder with files type rm -r foldername

To list files in folder type ls

To see hidden dot files in the folder type ls -a

To change folder type cd folder path

To see running processes type ps aux | less

To see running processes live type top

Here are some useful apt-get commands for N900 terminal :

apt-get update : Fetches updates from repositories

apt-get autoclean : Removes .deb files for packages that are no longer installed on your system

apt-get autoremove : Removes packages that were installed by other packages and are no longer needed

apt-get purge : Removes unnecessary packages and configuration files or something like that :) I'm no linux experts but when i run this i gain some space on rootfs

apt-get install <package name> :  Pulls and installs given package from repositories. Installed package will not be visible in Application manager!

apt-get remove <package_name>: Removes an installed package, leaving configuration files intact

apt-get purge <package_name>: Removes a package and the associated configuration files

See also Useful Commands for Nokia N900 terminal

Have you heard Nokia N900? One of the most capable smartphones mobile computers around. It used to run on 600MHz Arm cortex cpu, not anymore! Hackers managed to over-clock it to 1GHz.

Looks like it can handle it very well. At the moment overclocking requires to flash it with non stock kernel but I'm sure they'll find a simpler way!