Files and Directories

Everything lives in one big tree. There are no drive letters — no C: — just / (the root) at the top, with everything else below it.

The lay of the land

Directory	What's in it
/	The root — the very top
/home/paul	Your personal files (your home directory)
/etc	System configuration files
/var	Files that change a lot (logs, mail)
/tmp	Scratch space — may be wiped on reboot
/usr	Programs and their supporting files
/bin, /sbin	Essential programs (often links into /usr now)

You mostly live in /home/paul. The rest you visit, carefully.

Moving around

pwd        # where am I?
ls         # what's here?
cd Documents   # go into Documents (relative to here)
cd /etc        # go to /etc (absolute — starts from the root)
cd ~           # go home (~ is shorthand for your home directory)
cd ..          # go up one level
cd -           # go back to where you just were

Check: After cd ~, pwd prints /home/<your-username>.

Absolute vs. relative paths

• /etc/hosts — absolute: starts at the root, works from anywhere.
• Documents/notes.txt — relative: starts from where you are now.

If a path starts with /, it's absolute. Otherwise it's relative. Mixing these up is the #1 cause of "file not found."

Shortcuts worth knowing

Shortcut	Meaning
~	Your home directory
.	The current directory
..	The parent directory
-	The previous directory (with cd)

Seeing what's there

ls          # names, in columns
ls -l       # long format: permissions, owner, size, date
ls -la      # long format including hidden files (names starting with .)
ls -lh      # human-readable sizes (4.0K instead of 4096)

Hidden files start with a dot (.bashrc, .config). They're hidden from plain ls to reduce clutter, not for security — ls -a shows them. Your shell's configuration lives in these.

Making and removing

mkdir projects        # make a directory
mkdir -p a/b/c        # make nested directories all at once
touch notes.txt       # create an empty file (or update its timestamp)
rm notes.txt          # delete a file
rmdir projects        # delete an EMPTY directory
rm -r projects        # delete a directory AND everything in it

Careful: rm does not have an undo. Deleted files don't go to a trash can — they're gone. And rm -r on the wrong directory is the classic disaster. Two rules:

1. Never type rm -rf with a path you haven't double-checked. (The -f means "don't ask me, just do it.")
2. Never run rm -rf / or rm -rf ~ — the first tries to delete the whole system, the second your entire home directory. Modern rm refuses / without extra flags, but don't rely on that.

Check: After mkdir testdir && ls, you see testdir in the listing. After rmdir testdir, it's gone.

Copying and moving

cp notes.txt notes-backup.txt      # copy a file
cp -r projects projects-backup     # copy a directory (-r = recursive)
mv notes.txt Documents/            # move a file into Documents/
mv old.txt new.txt                 # rename a file (move within a folder)

mv is both "move" and "rename" — renaming is just moving to a new name in the same place. There is no separate rename command.

Next: Working with Files