Terminal Cheat Sheet

1 – SYSTEM INFORMATION

# Display Linux system information uname -a

Display kernel release information

uname -r

Show which version of Red Hat installed

cat /etc/redhat-release

Show how long the system has been running + load

uptime

Show system host name

hostname

Display all local IP addresses of the host.

hostname -I

Show system reboot history

last reboot

Show the current date and time

date

Show this month's calendar

cal

Display who is online

w

Who you are logged in as

whoami

2 – HARDWARE INFORMATION

# Display messages in kernel ring buffer dmesg

Display CPU information

cat /proc/cpuinfo

Display memory information

cat /proc/meminfo

Display free and used memory ( -h for human readable, -m for MB, -g for GB.)

free -h

Display PCI devices

lspci -tv

Display USB devices

lsusb -tv

Display DMI/SMBIOS (hardware info) from the BIOS

dmidecode

Show info about disk sda

hdparm -i /dev/sda

Perform a read speed test on disk sda

hdparm -tT /dev/sda

Test for unreadable blocks on disk sda

badblocks -s /dev/sda

3 – PERFORMANCE MONITORING AND STATISTICS

# Display and manage the top processes top

Interactive process viewer (top alternative)

htop

Display processor related statistics

mpstat 1

Display virtual memory statistics

vmstat 1

Display I/O statistics

iostat 1

Display the last 100 syslog messages (Use /var/log/syslog for Debian based systems.)

tail -100 /var/log/messages

Capture and display all packets on interface eth0

tcpdump -i eth0

Monitor all traffic on port 80 ( HTTP )

tcpdump -i eth0 'port 80'

List all open files on the system

lsof

List files opened by user

lsof -u user

Display free and used memory ( -h for human readable, -m for MB, -g for GB.)

free -h

Execute "df -h", showing periodic updates

watch df -h

4 – USER INFORMATION AND MANAGEMENT

# Display the user and group ids of your current user. id

Display the last users who have logged onto the system.

last

Show who is logged into the system.

who

Show who is logged in and what they are doing.

w

Create a group named "test".

groupadd test

Create an account named john, with a comment of "John Smith" and create the user's home directory.

useradd -c "John Smith" -m john

Delete the john account.

userdel john

Add the john account to the sales group

usermod -aG sales john

5 – FILE AND DIRECTORY COMMANDS

# List all files in a long listing (detailed) format ls -al

Display the present working directory

pwd

Create a directory

mkdir directory

Remove (delete) file

rm file

Remove the directory and its contents recursively

rm -r directory

Force removal of file without prompting for confirmation

rm -f file

Forcefully remove directory recursively

rm -rf directory

Copy file1 to file2

cp file1 file2

Copy source_directory recursively to destination. If destination exists, copy source_directory into destination, otherwise create destination with the contents of source_directory.

cp -r source_directory destination

Rename or move file1 to file2. If file2 is an existing directory, move file1 into directory file2

mv file1 file2

Create symbolic link to linkname

ln -s /path/to/file linkname

Create an empty file or update the access and modification times of file.

touch file

View the contents of file

cat file

Browse through a text file

less file

Display the first 10 lines of file

head file

Display the last 10 lines of file

tail file

Display the last 10 lines of file and "follow" the file as it grows.

tail -f file

6 – PROCESS MANAGEMENT

# Display your currently running processes ps

Display all the currently running processes on the system.

ps -ef

Display process information for processname

ps -ef | grep processname

Display and manage the top processes

top

Interactive process viewer (top alternative)

htop

Kill process with process ID of pid

kill pid

Kill all processes named processname

killall processname

Start program in the background

program &

Display stopped or background jobs

bg

Brings the most recent background job to foreground

fg

Brings job n to the foreground

fg n

7 – FILE PERMISSIONS

PERMISSION EXAMPLE

U G W rwx rwx rwx chmod 777 filename rwx rwx r-x chmod 775 filename rwx r-x r-x chmod 755 filename rw- rw- r-- chmod 664 filename rw- r-- r-- chmod 644 filename

NOTE: Use 777 sparingly!

LEGEND U = User G = Group W = World

r = Read w = write x = execute - = no access

8 – NETWORKING

# Display all network interfaces and IP address ip a

Display eth0 address and details

ip addr show dev eth0

Query or control network driver and hardware settings

ethtool eth0

Send ICMP echo request to host

ping host

Display whois information for domain

whois domain

Display DNS information for domain

dig domain

Reverse lookup of IP_ADDRESS

dig -x IP_ADDRESS

Display DNS IP address for domain

host domain

Display the network address of the host name.

hostname -i

Display all local IP addresses of the host.

hostname -I

Download http://domain.com/file

wget http://domain.com/file

Display listening tcp and udp ports and corresponding programs

netstat -nutlp

9 – ARCHIVES (TAR FILES)

# Create tar named archive.tar containing directory. tar cf archive.tar directory

Extract the contents from archive.tar.

tar xf archive.tar

Create a gzip compressed tar file name archive.tar.gz.

tar czf archive.tar.gz directory

Extract a gzip compressed tar file.

tar xzf archive.tar.gz

Create a tar file with bzip2 compression

tar cjf archive.tar.bz2 directory

Extract a bzip2 compressed tar file.

tar xjf archive.tar.bz2

10 – INSTALLING PACKAGES

# Search for a package by keyword. yum search keyword

Install package.

yum install package

Display description and summary information about package.

yum info package

Install package from local file named package.rpm

rpm -i package.rpm

Remove/uninstall package.

yum remove package

Install software from source code.

tar zxvf sourcecode.tar.gz cd sourcecode ./configure make make install

11 – SEARCH

# Search for pattern in file grep pattern file

Search recursively for pattern in directory

grep -r pattern directory

Find files and directories by name

locate name

Find files in /home/john that start with "prefix".

find /home/john -name 'prefix*'

Find files larger than 100MB in /home

find /home -size +100M

12 – SSH LOGINS

# Connect to host as your local username. ssh host

Connect to host as user

ssh user@host

Connect to host using port

ssh -p port user@host

13 – FILE TRANSFERS

# Secure copy file.txt to the /tmp folder on server scp file.txt server:/tmp

Copy *.html files from server to the local /tmp folder.

scp server:/var/www/*.html /tmp

Copy all files and directories recursively from server to the current system's /tmp folder.

scp -r server:/var/www /tmp

Synchronize /home to /backups/home

rsync -a /home /backups/

Synchronize files/directories between the local and remote system with compression enabled

rsync -avz /home server:/backups/

14 – DISK USAGE

# Show free and used space on mounted filesystems df -h

Show free and used inodes on mounted filesystems

df -i

Display disks partitions sizes and types

fdisk -l

Display disk usage for all files and directories in human readable format

du -ah

Display total disk usage off the current directory

du -sh

15 – DIRECTORY NAVIGATION

# To go up one level of the directory tree. (Change into the parent directory.) cd ..

Go to the $HOME directory

cd

Change to the /etc directory

cd /etc

Command	Description
ls	Lists all files and directories in the present working directory
ls-R	Lists files in sub-directories as well
ls-a	Lists hidden files as well
ls-al	Lists files and directories with detailed information like permissions,size, owner, etc.
cd or cd ~	Navigate to HOME directory
cd ..	Move one level up
cd	To change to a particular directory
cd /	Move to the root directory
cat > filename	Creates a new file
cat filename	Displays the file content
cat file1 file2 > file3	Joins two files (file1, file2) and stores the output in a new file (file3)
mv file "new file path"	Moves the files to the new location
mv filename new_file_name	Renames the file to a new filename
sudo	Allows regular users to run programs with the security privileges of the superuser or root
rm filename	Deletes a file
man	Gives help information on a command
history	Gives a list of all past commands typed in the current terminal session
clear	Clears the terminal
mkdir directoryname	Creates a new directory in the present working directory or a at the specified path
rmdir	Deletes a directory
mv	Renames a directory
pr -x	Divides the file into x columns
pr -h	Assigns a header to the file
pr -n	Denotes the file with Line Numbers
lp -nc , lpr c	Prints "c” copies of the File
lp-d lp-P	Specifies name of the printer
apt-get	Command used to install and update packages
mail -s 'subject'	Command to send email
-c 'cc-address'
-b 'bcc-address'
'to-address'
mail -s "Subject"	Command to send email with attachment
to-address < Filename
Linux File Permissions
File Permission commands
Command	Description
ls-l	to show file type and access permission
r	read permission
w	write permission
x	execute permission
-=	no permission
Chown user	For changing the ownership of a file/directory
Chown user:group filename	change the user as well as group for a file or directory
Environment Variables command
Command	Description
echo $VARIABLE	To display value of a variable
env	Displays all environment variables
VARIABLE_NAME= variable_value	Create a new variable
Unset	Remove a variable
export Variable=value	To set value of an environment variable
User management commands of linux
Command	Description
sudo adduser username	To add a new user
sudo passwd -l 'username'	To change the password of a user
sudo userdel -r 'username'	To remove a newly created user
sudo usermod -a -G GROUPNAME USERNAME	To add a user to a group
sudo deluser USER GROUPNAME	To remove a user from a group
finger	Shows information of all the users logged in
finger username	Gives information of a particular user
Networking command
Command	Description
SSH username@ip-address or hostname	login into a remote Linux machine using SSH
Ping hostname="" or =""	To ping and Analyzing network and host connections
dir	Display files in the current directory of a remote computer
cd "dirname"	change directory to "dirname” on a remote computer
put file	upload ‘file' from local to remote computer
get file	Download ‘file' from remote to local computer
quit	Logout
Process command
Command	Description
bg	To send a process to the background
fg	To run a stopped process in the foreground
top	Details on all Active Processes
ps	Give the status of processes running for a user
ps PID	Gives the status of a particular process
pidof	Gives the Process ID (PID) of a process
kill PID	Kills a process
nice	Starts a process with a given priority
renice	Changes priority of an already running process
df	Gives free hard disk space on your system
free	Gives free RAM on your system
VI Editing Commands
Command	Description
i	Insert at cursor (goes into insert mode)
a	Write after cursor (goes into insert mode)
A	Write at the end of line (goes into insert mode)
ESC	Terminate insert mode
u	Undo last change
U	Undo all changes to the entire line
o	Open a new line (goes into insert mode)
dd	Delete line
3dd	Delete 3 lines
D	Delete contents of line after the cursor
C	Delete contents of a line after the cursor and insert new text. Press ESC key to end insertion.
dw	Delete word
4dw	Delete 4 words
cw	Change word
x	Delete character at the cursor
r	Replace character
R	Overwrite characters from cursor onward
s	Substitute one character under cursor continue to insert
S	Substitute entire line and begin to insert at the beginning of the line
~	Change case of individual character