Linux command	Description
example	start example where example is a program found in the $PATH
./example	start example (allocated in current dir.)
adduser	add a user
rmuser	remove a user
passwd	change password
cd x or cd /x	go to directory x
cd .. or cd ../ or cd /..	go back one directory
ls or dir	list a directory
cat	display a textfile on the terminal Examples: cat /proc/meminfo - more memory info cat /proc/pci - list pci devices, interrupts, io cat /proc/cpuinfo - cpu info cat /proc/version - kernel and gcc version info cat /proc/ioports – input/output range of devices
mv x y	move or rename file x to file y
cp x y	copy file x to file y
rm x	delete a file rm -r /old_stuff - correct rm -r / old_stuff – common mistake leaving space between / and the directory name. This will wipe your system
mkdir x	make a directory
rmdir x	remove a directory
rm -r x	remove directory x and all its underlying files
df or df x	Show free space on device x
top	view memory status (q to quit)
man x	get a manual page about command x
less x or more x	view text file x
echo	print something on the screen mainly used in scripts
mc	similar to Norton Commander in DOS
mount	to make a device usable to the system (CD-ROM,other HDD)
umount	remove the device from being usable to the system
halt	to shutdown. It will also power off if APM or ACPI is being used
reboot or ([ctrl] + [alt] + [del])	to reboot the system
chmod <permissions> <file>	change file permissions
chown <owner:group> <file>	change file ownership
ls -l x	perform a detailed directory listing for file or directory x
ln -s x y	make a symbolic link to x called y
find x -name y -print	find file y, begin the search from within directory x and print the results to the screen
ps	to view all running processes
kill x	to terminate process x (x is PID from ps)
killall -KILL pgm	to kill the program called pgm
killall -HUP pgm	to force program pgm to restart - used in case configuration is changed
lilo	to write boot information changes to disk
ldd	shows the needed shared libraries
ldconfig	updates shared libraries
lsmod	shows loaded modules

Linux directories	Directory function
/	the root of the directory tree
/dev	the device pointer directory all devices have an entry here
/bin	main CLI executables
/sbin	main CLI system executables
/boot	location of the kernel and boot information required to boot the system
/etc	system configuration files
/root	root user home directory
/home	normal user base directory
/lib	system libraries and kernel modules
/usr	main user binary,documentation, library location eg. XFree86 and other X apps are here
/opt	extra binary/documentation,library location - eg.KDE
/var	system log files,spoolers,etc
/tmp	temporary folder for running applications that need temp files
/proc	includes files with information about the system
/mnt	filesystem mount point for devices (cdrom, usb etc.)

Linux configuration/script file	Description
/etc/lilo.conf	boot loader configuration file – you must run "lilo" after any changes
/etc/modprobe.conf	kernel module loader configuration used by the modprobe command
/etc/inittab	system runlevel configuration file - tells init what to do for each runlevel
/etc/fstab	filesystem mounting configuration file - used by the mount command
/etc/ld.so.conf	library configuration file - used by the ldconfig command to find libraries
/etc/inetd.conf	tcp wrapper configuration - used to start ftp and other network daemons
/etc/hosts	local host resolution file - manually enter hosts you want to connect to if they are not on DNS
/etc/HOSTNAME	system hostname file
/etc/profile	system defaults for bash login default paths,colours,etc
/etc/rc.d/rc.0	system halt script - run when you issue halt
/etc/rc.d/rc.6	system reboot script - run when you issue reboot or [ctrl] + [alt] + [del]
/etc/rc.d/rc.K	runlevel 1 or system administration mode
/etc/rc.d/rc.S	main system boot script - run when you boot up
/etc/rc.d/rc.M	main local startup script - activates other services you have chosen
/etc/rc.d/rc.sysvinit	SysV Init script starter
/etc/rc.d/rc.inet1	network startup script
/etc/rc.d/rc.modules	system module loader - run at startup
/etc/rc.d/rc.hotplug	hotplug starter script - for USB and PCI hotplug devices
/etc/rc.d/rc.pcmcia	pcmcia service script - for use with laptops
/etc/rc.d/rc.local	local startup script for user space programs
/etc/X11/xorg.conf	Xorg configuration file