Listing contents

ls -dlh	List the files and directories with their permissions and size	d = 'directory', list the directory instead of the contents l = 'long listing', provide a lot of details h = 'human readable', print the size in KB, MB, GB,...
ls -dalh	Include hidden files and folders	a = 'all', include hidden files and folders d = 'directory', list the directory instead of the contents l = 'long listing', provide a lot of details h = 'human readable', print the size in KB, MB, GB,...
ls <word>	List files and directories containing the word.	'*' is a wildcard, replacing any string of any length.

Managing files

mv <filename>{,.back}	Rename file with <filename> to <filename.back>	{...} is brace expansion. It replaces the complete structure by repeating in a particular way the content in it. Here the result is 'mv <filename> <filename>.back'.
rm -rf <files>	Forcefully remove file.	r = recursively. Also remove all subdirectories and their contents f = force. Do not ask for confirmation.
rm -rf <string>	Forcefully remove files which contain <string> in their name
chown -R username:groupname <directory_name/>	change directory and all its contents to be owned by user username and group groupname.	R = recursively. Also act on all subdirectories and their contents
chmod u+x <file>	Set the execution permissions to file filename	u = user. Apply for the user that owns the file only. Other options: g (group) and o (others) + = add permission. Other option: - (remove permission) x = execute permission. Other options: r (read), w (write).

grep <string> <file>	Display lines in file <file> containing the string <string>
grep <string> *	Search in all files in current directory
grep -R <string> *	Search in all files in current directory and all subdirectories	R = recursively. Also remove all subdirectories and their contents
grep -Rl <string> *	List the file names in which the string appears	R = recursively. Also remove all subdirectories and their contents l = list. Only show file names.
find /usr/local/bin -type l	Find all symbolic links in the directory /usr/local/bin	-type l = link. Other options: f (file), d (directory)
find -type d -name bin	find directories with name bin in current directory.
find -name \*.gtf	find files or directories ending with .gtf.	the * needs to be escaped for find to work.
find . -type f -perm +111 -exec ln -s `pwd`/{} /usr/local/bin \;	Find in current directory all files with permissions set, and put a symbolic link to them in the folder /usr/local/bin	perm = permissions, according to the numerical permission settings. exec = execute following command. Replace '{}' with the found item. End always with '\;'

ls -lhd *	List the sizes of the files in current directory
du -sh *	List the size of files in current directory
du -sh */	List the sizes of the directories in current directory
df -h	List the space left on the storage
df -h .	List the space left on the currently used disk
mount	Show which disks are available on the system
showmount -e <host>	List the NFS network shares offered by host <host> (IP address or hostname)

ctrl+shift+T	Fire up the terminal (can be customized of course)
ctrl+U	clear line
ctrl+D	close terminal (log out)
ctrl+a	move to beginning of line
ctrl+e	move to end of line
alt+f	move forward one word
alt+b	move backwards one word
ctrl+l	clear sceen, leaving current line
pushd <path_to_dir>	Store the path to the directory <path_to_dir>, and cd to it
popd	Enter the last stored path with pushd.
sudo su -	Become superuser.

ln -s <what> <towhere>	Preferentially move first to the folder where to create the symbolic link
unlink	Remove a link