Linux Commands Cheat Sheet

System Information

Display Linux system information

uname -a

Display kernel release information

uname -r

Show OS information (distribution and version)

cat /etc/os-release

Show system uptime and load

uptime

Show system hostname

hostname

Display all local IP addresses

hostname -I

Show system reboot history

last reboot

Show current date and time

date

Show this month's calendar

cal

Show who is currently logged in

w

Show your current username

whoami

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 (human readable)

free -h

Display PCI devices

lspci -tv

Display USB devices

lsusb -tv

Display hardware info from BIOS

dmidecode

Show info about disk sda

hdparm -i /dev/sda

Perform read speed test on disk sda

hdparm -tT /dev/sda

Performance Monitoring

Display and manage 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

tail -100 /var/log/messages

Monitor all traffic on port 80 (HTTP)

tcpdump -i eth0 'port 80'

List all open files on the system

lsof

Execute "df -h", showing periodic updates

watch df -h

User Management

Display user and group IDs

id

Display last logged in users

last

Show who is logged into the system

who

Show who is logged in and what they're doing

w

Create a group named "test"

groupadd test

Create a user account with home directory

useradd -c "John Smith" -m john

Delete the user account "john"

userdel john

Add user to a group

usermod -aG sales john

File and Directory Commands

List all files in long format

ls -al

Display present working directory

pwd

Create a directory

mkdir directory

Remove (delete) file

rm file

Remove directory recursively

rm -r directory

Force removal without prompting

rm -f file

Copy file1 to file2

cp file1 file2

Copy directory recursively

cp -r source_dir destination

Rename or move file

mv file1 file2

Create symbolic link

ln -s /path/to/file linkname

Create an empty file or update timestamp

touch file

File Content Commands

View the contents of a 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 and follow updates

tail -f file

Search for pattern in file

grep pattern file

Search recursively for pattern in directory

grep -r pattern directory

Find files and directories by name

find /path -name filename

Find files larger than 100MB

find /path -size +100M

Process Management

Display your currently running processes

ps

Display all running processes

ps -ef

Display process information for processname

ps -ef | grep processname

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

Bring most recent background job to foreground

fg

Bring job n to the foreground

fg n

File Permissions

Change file permissions (full access)

chmod 777 filename

Change file permissions (rwx for owner, rx for group/world)

chmod 755 filename

Change file permissions (rw for owner, r for group/world)

chmod 644 filename

Change file owner

chown user:group filename

Change file permissions recursively

chmod -R 755 directory

Change file owner recursively

chown -R user:group directory

Networking

Display all network interfaces and IP address

ip a

Display eth0 address and details

ip addr show dev 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

Download file from URL

wget http://domain.com/file

Display listening ports and programs

netstat -nutlp

Archives (TAR Files)

Create tar archive

tar cf archive.tar directory

Extract the contents from archive

tar xf archive.tar

Create a gzip compressed tar file

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

Package Installation

Update package lists (Debian/Ubuntu)

apt update

Install package (Debian/Ubuntu)

apt install package

Remove package (Debian/Ubuntu)

apt remove package

Search for package (Red Hat/CentOS)

yum search keyword

Install package (Red Hat/CentOS)

yum install package

Remove package (Red Hat/CentOS)

yum remove package

SSH and File Transfer

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

Secure copy file to remote host

scp file.txt server:/path

Copy files from remote host to local

scp server:/path/file.txt /local/path

Synchronize local to remote

rsync -avz /local/ server:/remote/

Disk Usage

Show free and used space on mounted filesystems

df -h

Show free and used inodes on mounted filesystems

df -i

Display disk usage for all files and directories

du -ah

Display total disk usage off the current directory

du -sh

Shell Shortcuts

Clear the terminal screen

Ctrl+L

Stop the current command

Ctrl+C

Sleep the current command

Ctrl+Z

End of file (EOF)

Ctrl+D

Cut from cursor to start of line

Ctrl+U

Cut from cursor to end of line

Ctrl+K

Paste from clipboard

Ctrl+Y

Search command history

Ctrl+R