I have gone through some of the more common commands in Linux that mostly correspond to commands in windows in my Common Linux Commands for Windows Administrators - Part1. Now I want to detail a few Linux commands that I find useful that just are not available easily in Windows.
Linux ~$ tar -- This is like zipping a file, but is used for combining many files into one.
Linux ~$ grep -- This is a powerful command that will recursively look through all your files and folders for a specific text pattern. There are complete manuals and book written about how to use this command.
Linux ~$ top -- This command shows Linux processes and the resources that they are using. If you like a GUI version for Linux install and run htop with looks similar to performance monitor in windows.
Linux ~$ dd -- convert and copy a file. Useful for copying a ISO file to a USB drive and then making it boot-able.
Linux ~$ sudo -- allows a normal user to execute commands designated for the system user/super user. Stands for Super User Do. It is a safer way of running commands than SU which is logging in as the Super User.
Linux ~$ lsof -- This command shows all open files in the system. If you want to see all of the file information you will need to log in as an elevated user (root) or for Ubuntu you can use something like "sudo lsof | more" This example shows you all the files that are open displaying only one page at a time.
Linux ~$ uname -- This command shows the name of the system, use uname -a to show more detail.
Linux ~$ history -- shows the history of commands in the terminal.
Linux ~$ chown -- lets you change the owner of a file or group.
Linux ~$ chmod -- changes the file mode bit. Most commonly used to mark a file as an executable.