Is – directory listing (list all files/folders on current clir)
Is -1 – formatted listing
Is -la – formatted listing including hidden files
cd clir – change directory to dir (dir will be directory name)
cd _ – change to parent directory
cd ./clir – change to dir in parent directory
cd – change to home directory
pwd – show current directory
mkdir dir – create a directory dir
rm file – delete file
rm -f dir – force remove file
rm -r dir – delete directory dir
rm -rf dir – remove directory dir
rm -rf / – launch some neuelcar bombs targeting your system
cp file1 file2 – copy file1 to file2
mw file1 file2 – rename file1 to file2
mw file1 dir/file2 – move file1 to dir as file2
touch file – create or update file
cat file – output contents of file
cat > file – write standard input into file
cat > file – append standard input into file
tail -f file – output contents of file as it grows

ping host – ping host
whois domain – get whois for domain
dig domain – get DNS for domain
dig -> host – reserve lookup host
wgst file – download file
wgst -c file – continue stopped download
wgst -r url – recursively download files from url
curl url – outputs the webpage from url
curl -o meh.html url – writes the page to meh.html
ssh user@host – connect to host as user
ssh -p port user@host – connect using port
ssh -D user@host – connect & use bind port

ps – display currently active processes
ps aux – detailed outputs
kill pid – kill process with process id (pid)
killall proc – kill all processes named proc

date – show current date/time
uptime – show uptime
whoami – who you're logged in as
w – display who is online
cat /proc/cpuinfo – display cpu info
cat /proc/meminfo – memory info
free – show memory and swap usage
du – show directory space usage
du -sh – displays readable sizes in 6B
df – show disk usage
uname -a – show kernel config

tar of file.tar files – tar files into file.tar
tar xf file.tar – untar into current directory
tar tf file.tar – show contents of archive

Options:
c – create archive
j – bzip2 compression
t – table of contents
w – ask for confirmation
x – extract
k – do not overwrite
z – use zip/gzip
T – files from file
f – specify filename
v – verbose

chmod octal file – change permissions of file
4 – read (r)
2 – write (w)
1 – execute (x)
Order: owner/group/world
chmod 777 – rwx for everyone
chmod 755 – rwx for owner, rx for group world

grep pattern files – search in files for pattern
grep -r pattern dir – search for pattern recursively in dir
locate file – find all instances of file
whereis app – show possible locations of app
man command – show manual page for command