Linux commands

• pwd – prints your working (or current) directory
• cd – change directory
• ls – list the files in the working directory
• cp – copy files and directories
• mv – move or rename files and directories
• rm – remove files and directories
• mkdir – create a directory 

Here are some basic permission commands:

• chmod – modify file access rights
• su – temporarily become the superuser
• chown – change file ownership
• chgrp – change a file’s group ownership
• of commands for viewing system information:

uname – show kernel version and system architecture. (several options available including -s – kernel, -o for operating system. -a prints all options)
sudo command - run command as root
sudo su - open a root shell
sudo su user - open a shell as user
sudo -k - forget sudo passwords
df -h – Show free space on mounted filesystems
fdisk -l – Show disks partitions sizes and types (run as root)



Network

ifconfig - show network information
iwconfig - show wireless information
sudo iwlist scan - scan for wireless networks
sudo /etc/init.d/networking restart - reset network
(file) /etc/network/interfaces - manual configuration
ifup interface - bring interface online
ifdown interface - disable interface

Firewall

ufw enable - turn on the firewall
ufw disable - turn off the firewall
ufw default allow - allow all connections by default
ufw default deny - drop all connections by default
ufw status - current status and rules
ufw allow port - allow traffic on port
ufw deny port - block port
ufw deny from ip - block ip adress


Manipulating files and directories

cp -Copy a file.
cp -i -Copy a file and ask before overwriting.
cp -r -Copy a directory with its contents.
mv -Move or rename a file.
mv -i -Move or rename a file and ask before overwriting.
rm -Remove a file.
rm -r -Remove a directory with its contents.
rm -i -Ask before removing a file. Good to use with the -r option.
mkdir -Make a directory.
rmdir -Remove an empty directory.

hostname - Shows the host name of the system you are on
whoami Displays your login name
date - Displays what your machine thinks the date is
who - Shows who is logged into the machine
rwho-a -Shows all users logged into the server network
finger Shows info on chosen user

uptime - Shows the systems uptime
PS - Shows the current user processes
PS -A - Shows all process on the system
uname -A -Displays all info on your host.
free -Shows the free memory in KB
df -h -Shows the disk space details
cat/proc/cpuinfo -Shows the CPU information
cat/proc/filesystems -Shows the file system information in use
cat/etc/printcap -Shows if any printers are hooked up
lsmod -Shows the kernel modules loaded

Arrow Up: scrolls and edits the command history, press enter to activate.
Shift+pgup: scrolls terminal output up
Shift+pgdown: scrolls terminal output down
CTRL-ALT+DEL reboots the system
Shutdown -h now turns the system off
CTRL C kills the current process
CTRL S Stops the tranfer to the terminal
CTRL Q Resumes the transfer to the terminal
CTRL Z Puts the current process in the background.

Recovery - Type the phrase “REISUB” while
holding down Alt and SysRq (PrintScrn) with
about 1 second between each letter. Your system
will reboot.
lsb_release -a - get Ubuntu version
uname -r - get kernel version
uname -a - get all kernel information


Moving around in the file system

pwd "Print working directory" - show what dir you're in.
ls -List the contents of a dir.
ls -l -List the contents of a dir and show additional info of the files.
ls -a -List all files, including hidden files.
cd -Change directory.
cd .. -Go to the parent directory.



Malicious Commands You Should (NOT USE) unless you know what you're doing.

This commands will erase your hard drive:
sudo mkfs (This will format your hard drive)
sudo mkfs.ext3 (This will format your hard drive)
sudo mkfs.bfs (This will format your hard drive)
sudo mkfs.cramfs (This will format your hard drive)
sudo mkfs.ext2 (This will format your hard drive)
sudo mkfs.minix (This will format your hard drive)
sudo mkfs.msdos (This will format your hard drive)
sudo mkfs.reiserfs (This will format your hard drive)
sudo mkfs.vfat (This will format your hard drive)

This commands can damage your operating system.

sudo rm -rf / (This will delete all your files on your system)
sudo rm -rf * (This will delete all the files in the current folder)
rm -rf * or rm -rf *.* (This will delete all the files in the current folder)
rm -rf ~/ & (This will destroy your home directory)