In this tutorial we'll look at the first prerequisite skills listed in the Red Hat exam prep guide. Linux administrators need an in depth knowledge of standard command line tools. As described in the prerequisites they allow you to create, remove, view, and investigate files in directories. We'll examine the commands from the list of prerequisites one by one. The LS command lists files in the current directory. But wait a second, Linux commands and file names are case sensitive. Most commands are lower case. The LS command lists files in the current directory with the right switches the LS command can be especially useful in finding permissions. The LS-L lists permissions in the left hand column. It lists file sizes in the middle, for example, the change log -2.6.19.1 is about 27 kilobytes large. It can help you list hidden files. Hidden files start with a dot. It can help you find the newest files in a directory. If you specify LS-T it lists the newest file first. You can reverse the order if you run LS-TR the newest file is listed last. It can combine switches. I sometimes run the LS-LTAR command which lists all files in the current directory including hidden files in reverse chronological order. Next, the CP command copies files. One straight forward way to use it is to back something up. For example, before I edit the SMB dot com configuration file I usually back it up. A straight forward way to do so is to copy from the original file name to a logical backup file name as shown. Now I can edit the SMB dot com configuration file and if I screw it up I can restore from a back up. With various switches I can copy directories recursively. For example I often use the copy with archives recursive command, CP-AR to copy all files in subdirectories. For example, if I wanted to copy the RHCT directory for my home directory, the home directory is symbolized by the tilda RHCT to the temp directory I'd run this command and now I can find a copy of my RHCT directory in the temp directory along with the files they're in. Next the move command copies files and then deletes the original. One way it can be useful is to restore for a backup. Let's say I screwed things up with my Samba configuration file. I run the move command MV and I'm restoring from my back up file and now the backup file no longer exists. It's been used to overwrite the original file. Next the remove command, RM, deletes files and directories with the right switches can work recursively. For example the following command deletes all files and subdirectories from the home student RHCT subdirectory. But this command can be very dangerous if I make a mistake and put a space between the first slash and the rest of the command I would delete all files in my top level root directory and then everything would be gone and then the RM command would try to find the files in the home slash student slash RHCT subdirectory but by then my system would be a disaster. So use the RM-RF command with extreme caution. Now let's look at a couple of commands that can look inside files. The tail command can be especially useful for log files. For example if you're monitoring new logs you can run the following command in one console, it watches new messages, whoops, this requires root privileges, which I'll cover in another tutorial. And I can watch as new log messages are added to this file. The cad command is straight forward it lists the contents of a given file. Let's see how that works on the standard user password database file, we'll look at more commands in upcoming tutorials. But for now practice what you've learned. Check out the main pages for each of these commands; see what else you can learn. The tips and tricks you learn can save you time during the exam and in real life as a Linux administrator. Thank you and on to the next tutorial.