Basic Commands and Filesystem Overview

An overview of the Linux Filesystem and seven frequently-used Linux commands and examples of how to use them. For additional information about any of these commands, log onto an EECS machine and type

man command

Replace “command” with the actual command for which you want the manual page, for example man ls.

The filesystem structure of Linux is much different from Windows. It is good to know a few of these differences before you start.

In Windows, drives are mounted completely separately with drive letters. In Linux, drives are mounted in the filesystem. / is the root direcory of your boot drive filesystem. All mounted drives and filesystems in Linux exist somewhere under /. All of the default directories in / (known as standard subdirectories) have a meaning and intended use to keep the filesystem organized. Some examples are as follows:

Directory	Purpose
/	The root of the filesystem.
/bin	Stores essential programs such as shells, `ls`, etc.
/etc	Stores configurations for Linux, daemons, etc
/var	Stores variable data like log files, etc.
/home	Stores user home areas, like `C:\\Users` in Windows.
/dev	Stores device files.

In a Linux shell, there are two types of paths. There are absolute paths (beginning in /) that define a full path from the root directory and relative paths (paths that don't begin with /) that are relative to your current directory. Example:

/home/netid > cp some_file Documents
# this copies some_file from your current directory into the Documents directory in your current directory

/home/netid > mv classes/cosc102/my_file.log /tmp
# this moves the file my_file.log (absolute path /home/netid/classes/cosc102/my_file.log) to the absolute path /tmp)

The ls command lists directory contents.

Command	Effects
`ls`	Lists the contents of the current working directory.
`ls dir-name`	Lists the contents of the `dir-name` directory.
`ls -a`	Lists the contents of the current working directory, including files that begin with a dot. (Dotfiles are not listed unless the -a option is used.)
`ls -l`	Lists the contents of the current working directory in long format (including file owner, permissions, etc.).

The cd command changes the current (working) directory.

Command	Effects
`cd`	Changes to your home directory.
`cd foo`	Changes to the `foo` directory.
`cd ..`	Changes to the parent directory (i.e., move up one directory).

The cp command copies files and directories.

Command	Effects
`cp src-file dest-file`	Creates/overwrites `src-file` into `dest-file`.
`cp src-file dest-dir`	Copies/overwrites `src-file` into `dest-dir/src-file`.
`cp -R src-dir dest-dir`	Copies all files and subdirectories within the `src-dir` directory into the `dest-dir` directory. (The `-R` stands for “recursive”.)
`cp -i src dest`	Copies the file/directory src to the file/directory dest, but prompts if any files or directories would be overwritten. (The `-i` stands for “interactive”.)

The mv command moves or renames files and directories.

Command	Effect
`mv old-file new-file`	Renames the file `old-file` to `new-file`.
`mv src-file dest-dir`	Moves the file `src-file` into `dest-dir/src-file`.
`mv old-dir new-dir`
`mv old-dir existing-dir`	Moves the `old-dir` directory into the `existing-dir` directory.
`mv -i src dest`	Moves or renames `src` to `dest`, but prompts if any files or directories would be overwritten. (The `-i` stands for “interactive”.)

The rm command removes (i.e., deletes) files. (To remove directories, use rmdir if the directory is empty.)

Command	Effects
`rm foo`	Deletes the file `foo`.
`rm -r dir`	Deletes the `foo` directory, including all of its files and subdirectories. (The `-r` stands for “recursive”.)
`rm -i file`	Deletes the file `foo`, but prompts before actually deleting it. (The `-i` stands for “interactive”.)

The mkdir command makes a new directory.

Command	Effects
`mkdir foo`	Creates a new directory named `foo`.

The du command displays the amount of disk usage for specific files and directories.

Command	Effects
`du -s foo`	Summarizes the disk usage of a file/directory `foo` in KB.
`du -sh .`	Summarizes the disk usage of the current directory (represented by `.` in human-readable format (prints sizes using appropriate sizes such as KB, MB, GB) (`-h` stands for human-readable.)