Linux/Unix:
#List files and Directories.
ls
#Options include.
-l = List
-h = Human readable file/directory size
-a = Show hidden files/directories
#Change Directory
cd <pathname>
#Print ASCII character strings in large letters
banner <text>
#List running processes
ps
#Create a new directory
mkdir <directory name to be created>
#Print the working directory
pwd
#Recursively search for a file or directory
find <file or directory name>
#View full contents of file in terminal
cat <filename>
#Copy a file
cp <original filename> <copy filename>
#Move or rename a file
mv <original file> <new location or name>
#Run previous command as sudo.
sudo !!
#Display history file in terminal
history
#Run command with history ID <id>
!<id>
#Run last command via command name
!<command name>
#Search man pages with given keyword
apropos <keyword>
#Use stdout as an argument
xargs
#Show information of file
file <filename>
#Reverse search of history
ctrl + r <command>
Tip: Press ctrl + r to cycle to the next command etc
#Show current user
whoami
#Show logged in user with what process they are running etc
w
#Show logged in user
who
#Pause current session
ctrl + z
#Show current paused sessions
jobs
#Resume paused session
fg
#Send paused session to background
bg
#Show network interface information
ifconfig
#Show drive usage information
df
#Show memory usage information
free
#Ping a given IP or domain
ping <ip or domain>
#Open an SSH session with a given user and machine
ssh <user>@<machine IP or domain>
#Close an active SSH session or exit the terminal
exit
#Show logs of specified service
journalctl -u <service name>
#Show logs of specified process ID
journalctl _PID=<process id>
#Show all installed services
systemctl list-unit-files --type=service
#Terminate process
kill <process id>
#Create a file
touch <filename>
#Print the first 10 lines of a file to standard output
head <filename>
#Options include
-n [NUM] = Print the first NUM lines instead of 10
-n -[NUM] = Print all but the last NUM lines of a file
#Print the last 10 lines of a file to standard output
tail <filename>
#Options include
-n [NUM] = Print the last [NUM] lines instead of 10
-n +[NUM] = Print all lines starting with [NUM] until EOF
#Check the current system clock time
timedatectl
#Options include
set-time "yyyy-MM-dd hh:mm:ss" = Set the local time of the system clock directly
list-timezones = available timezones
set-timezone timezone = Set the system timezone
set-ntp on = Enable Network Time Protocol (NTP) synchronization
#View Date on terminal
date
#Change the permissions granted
chmod
#change a file's ownership
chown
#change the apparent root directory for the current running process and its children
chroot
#Edit file using vi
vi <file name>
#Edit file using nano
nano <file name>
#Displays active TCP connections, ports
netstat -tulpn
#Download from terminal
wget <url>
#unzip a file
unzip <filename>
#mount a drive
mount <drive name> <mount point>
#unmount a drive
umount <drive name>
#Switch to users
su <username>
#Switch to root
sudo su
#Find the location of source/binary file
whereis <file name>
#Manipulation of partition tables
fdisk
#Install, build, remove and manage Debian packages
dpkg
#Install, build, remove and manage Debian packages
apt-get
#Creates a new user account
adduser
#Creates a new group
groupadd
#Adds a user to a group
usermod
#Remove a user from a group
userdel
#Change password of user
passwd
#Check md5sum of file
md5sum <filename>
#Check sha1sum of file
sha1sum <filename>
#Prints the name of the terminal
tty
#Ftp on a remote host
ftp <host>
#Dns lookup
nslookup <host>
#Show domain information
host <host>
#Show detailed domain information
dig <host>
#View sttrings in a file
strings <filename>
#View file type
file <filename>
#Details on all Active Processes
top
#Determine system boot-up performance statistics
systemd-analyze
#find the files by name
locate <filename>