The “pwd” command prints the full name (the full path) of current/working directory. By default, right after ssh-ing to a Linux machine you would find yourself in your home directory, usually /home/. ssh to a cluster, type “pwd” and see if it returns ‘/home/’, where is your ISU NetID.

The “ls” command lists directory contents. ls command can be used with many options and has one optional argument. If you issue “ls -a” command in your home directory, you should see several files listed, some of the names starting with a dot. Now try issuing “ls” command without any options. You may not see any files at all. The ‘-a’ option tells ls to display hidden files – those files, whose name start with a dot.

Issue again the “ls -a” command. The first two directories in the list should be ‘.’ and ‘..’. Every directory on a Linux machine will have those two directories. The ‘.’ directory means current directory and the ‘..’ directory means parent directory, e.g. the directory one level up, that contains the current directory. For example, for /home/abc directory ‘.’ will mean /home/abc and the ‘..’ will mean /home. With no arguments “ls” command prints contents of the current directory. To see contents of the parent directory, issue “ls ..”. You should see a list of users on the system. You may guess that “ls .” command will provide same output as the “ls” command. To see contents of the root directory, issue “ls /”.

‘-l’ option tells ls command to use a long listing format, providing additional information about directory contents. Issue “ls -la” in your home directory. For each file the following information will be listed: file type, file permissions, file owner, group associated with the file (group owner), size, last modification date. File permissions are shown as three triplets: for the file owner, for the group owner and for everyone else on the system. For more information about file permissions, refer to the man page of chmod command: “man chmod”.

You can also use “ls” command on a regular file (non-directory). Usually you will use it with ‘-l’ option to get file information.

To create new directory use “mkdir” command. For example, to create directory TMP in the current directory issue either “mkdir TMP” or “mkdir ./TMP”. It’s a good practice to organize files by creating directories and putting files inside of them instead of having all files in one directory. Try to avoid using spaces and other special characters (except “_”) in file names on Linux. While almost any character can be used in a file name, it’s more complicated to refer to such names in CLI commands. Now, that you’ve created directory TMP in the current directory, what output do you think you will get if you issue “ls -a TMP” command? Check yourself.

In a graphical desktop environment to go to a different directory (folder), you would just click on the directory name. In the CLI you will use “cd” command (which stands for “change directory”). To go to the newly created TMP directory, issue “cd TMP”. Issue “pwd” to verify that you’re now in the new directory.

“cd ..” command will take you one level up. “cd /” will change current directory to root directory, while “cd” with no arguments will take you to your home directory.

Sometimes you may need to change directory to somewhere else, and then go back to the directory you were in. In this case you can use “cd -“ command which is equivalent to “cd $OLDPWD”.

There are several ways to create new file. Since usually you would want to write something in the new file, you can just use one of the text editors available on the cluster.

If you don’t know how to use vi/vim, we recommend using nano, which is a small and friendly editor. If you’re used to emacs, it’s also installed on our clusters.

Whether to create a new file or edit an existing file in the current directory, issue “nano ” command, where is the name of the file you would like to create/edit. Within nano use PgDn, PgUp and arrow keys to move cursor to the different part of the file. Pressing Enter key will create new line. At the bottom of the editor window you will find the list of hot keys for various actions with ‘^’ meaning Ctrl key. For example, among the commands you will see:

That means that to exit editor, you need to press Ctrl-X. Read carefully the questions that editor will ask. For example, it may ask if you would like to save changes that you’ve made to the file before closing the editor.

If you don’t need to edit file and just want to see the contents, you can use one of the following commands: “cat”, “less”, “head”, “tail”.

“cat ” will print contents of the file on the screen. Usually you would use it on small files. For larger files it’s better to use “less” command which initially will print only the first page. As in the “man” command, to navigate between pages, use PgDn, PgUp and arrow keys. Alternatively, you can use Space, ‘b’ and Enter keys. To search for a term, type ‘/’ and hit Enter. To repeat the same search, type ‘/’ and press Enter. To exit “less” command, use ‘q’ key.

If you need to see only the first N lines of a file, use “head -N” command. If number of lines is not specified, 10 lines will be displayed. Similarly, “tail -N” command will display last N lines of the file. It’s useful to display the end of a log file that is being actively written to.

“cp” command is used to copy files and directories. It requires at least two arguments.

To copy file file1 to a new file file2, issue “cp file1 file2” command. file2 will have the same contents as file1, but it will have new date stamp. Modifying one of the files will not affect the other file.

To copy file1 and file2 to a different directory, issue “cp file1 file2 ”. File /file1 will have the same contents as file1, and file /file2 will have the same contents as file2, but they will have new date stamps.

To copy directory dir1 with all the files and subdirectories to a different directory, issue “cp -r dir1 ”.

“mv” command is used to move or rename files and directories. It also requires at least two arguments.

To move file1 and file2 to a different directory, issue “mv file1 file2 ”. To move directory dir1 with all the files and subdirectories to a different directory, issue “mv dir1 ”.

“rm” command is used to remove files and directories. It requires at least one argument. Be careful with this command so that you don’t delete files that you meant to keep. To remove directory dir1 with all the files and subdirectories, issue “rm -r dir1”.