Basic linux commands

This is a list of all basic linux commands you should know.
Of course this is my personal opinion.
What do you think?

Files and navigation

ls - directory listing of current directory
ls -l - formatted listing
ls -la - formatted listing including hidden files
cd dir - change directory to dir (dir = name of directory)
cd .. - change to parent directory
cd - change to home directory
cd - - change to previous visited directory
cd ../dir - change to dir in parent directory
pwd - show current directory
mkdir dir - create a direcotry "dir"
rm filename - delete file
rm -f filename - force remove filename
rm -r dir - delete directory
rm -rf dir - force delete of directory
cp file1 file2 - copy file1 to file2
mv file1 file2 - rename file1 to file2
mv file1 dir/file2 - move file1 to dir as file2
touch filename - 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 - outputs contents of file as it grows

Networking

ping host - ping the host
whois domain - get whois for domain
dig domain - get DNS for domain
dig -x host - reverse lookup host
wget file - download file
wget -c file - continue stopped download
wget -r url - recusivley download files from url
curl url - outputs the webpage from url
curl -o output.html url - writes the page to output.html
ssh user@host - connect to host as user
ssh -p port user@host - connect using port
ssh -D user@host - connect & user bind port

Processes

ps - display currently active processes

ps aux - detailed outputs

kill pid - kill process with process id (pid)

killall proc - kill all processes named proc

System info

date - show current date/time
uptime - show uptime
whoami - who you are 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 GB
df - show disk usage
uname -a - show kernel config

Compressing

tar cf 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
• t - table of contents
• x - extract
• z - use zip/gzip
• f - specify filename
• j - bzip2 compression
• w - ask for confirmation
• k - do not overwrite
• T - files from file
• v - verbose

Permissions

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 - rw for owner, rx for group and world

Some others

grep pattern files - search in files for pattern

grep -r pattern dir - search for pattern recursively in directory

locate file - find all instances of file

whereis app - show possible locations of app

man command - show manual page for command