Linux Cheat Sheet

Discover essential Linux commands to enhance your networking skills. Perfect for both beginners and pros, start exploring now!

Linux Cheat Sheet Commands

Network engineers and system administrators frequently rely on these essential Linux commands for their daily tasks and critical operations.

To assist you, we've created a comprehensive Linux Cheat Sheet for your network or system management tasks. No more searching the internet for Linux commands—everything you need is right here. This cheat sheet will help you perform configuration tasks efficiently, much like other resources such as SONiC or ONiE Cheat Sheets.

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System Information Commands

uname -a Shows Linux system info
uname -r Shows kernel release info
cat /etc/redhat-release Shows installed redhat version
uptime Displays system running/life time
hostname Shows system host name
hostname -I Shows ip addresses of the host
last reboot Displays system reboot history
date Displays current date and time
cal Displays monthly calendar
mount Shows mounted filesystems

Ls Options

-a Display hidden files
-R Recursive list
-r Reverse order
-t Sort by last modified
-S Sort by file size
-l Long listing format
-1 One file per line
-m Comma-separated output
-Q Quoted output

Command Lists & Pipes

cmd1 ; cmd2 Run cmd1 then cmd2
cmd1 && cmd2 Run cmd2 if cmd1 is successful
cmd1 || cmd2 Run cmd2 if cmd1 is not successful
cmd& Run cmd in a subshell
cmd1 | cmd2 Stdout of cmd1 to cmd2
cmd1 |& cmd2 Stderr of cmd1 to cmd2

IO Redirection

cmd< file Input of cmd from file
cmd1 <(cmd2) Output of cmd2 as file input to cmd1
cmd> file Standard output (stdout) of cmd to file
cmd> /dev/null Discard stdout of cmd
cmd>> file Append stdout to file
cmd 2> file Error output (stderr) of cmd to file
cmd 1>&2 Stdout to the same place as stderr
cmd 2>&1 Stderr to the same place as stdout
cmd&> file Every output of cmd to file

File Operations

touch file1 Create file1
cat file1 file2 Concatenate files and output
less file1 View and paginate file1
file file1 Get the type of file1
cp file1 file2 Copy file1 to file2
mv file1 file2 Move file1 to file2
rm file1 Delete file1
head file1 Show the first 10 lines of file1
tail file1 Show the last 10 lines of file1
tail -F file1 Output the last lines of file1 as it changes

Search Files

grep pattern files Search for pattern in files
grep -i pattern files Case-insensitive search
grep -r pattern dir Recursive search in dir
grep -v pattern files Inverted search
grep -o pattern files Show matched part of the file only
find /dir/ -name name* Find files starting with name in dir
find /dir/ -user name Find files owned by name in dir
find /dir/ -mmin num Find files modified less than num
find /home -size +500M Find files larger than 500MB in /home
whereis command Locate the binary and source
locate file: x Find the location of file quickly

Bash Shortcuts

CTRL-c Stop current command
CTRL-z Sleep program
CTRL-a Go to the start of the line
CTRL-e Go to the end of the line
CTRL-u Cut from the start of the line
CTRL-k Cut to the end of the line
CTRL-r Search history
!! Repeat the last command
!abc Run the last command starting with "abc”
!abc:p Print the last command starting with "abc"
!$ Last argument of the previous command
ALT-. Last argument of the previous command
!* All arguments of the previous command
^abc^123 Run the previous command, replacing "abc" with "123"

Process Management

ps Show snapshot of processes
top Show real-time processes
kill pid: Kill the process with ID pid
pkill name: Kill processes with the name name
killall name Kill all processes with names
program & Start program in the background
bg List and resume stopped background jobs
fg Bring the most recent background job
fg x Bring job x to the foreground
nice Start a process with a given priority
renice Change the priority of an running process
pstree Display processes in a tree-like diagram
pmap Display a memory usage process map
lsof List files opened by running processes

Help Commands

command -h or command --help Review all available options of command
info command Find info documents about the command
whatis command Display a single-line command description
man UNIXCOMMAND View the detailed man page of command
apropos Search man pages for available commands

Hardware Information Commands

dmesg Display messages in the kernel ring buffer
cat /proc/cpuinfo Display CPU information
cat /proc/meminfo Display memory information
lspci -tv Display PCI devices
lsusb -tv Display USB devices
dmidecode Display DMI/SMBIOS information
hdparm -i /dev/sda Display information about disk sda
hdparm -tT /dev/sda Perform a read speed test on disk sda
badblocks -s /dev/sda Test for unreadable blocks on disk sda

Networking Commands

arp Display the ARP table of the device
arpwatch Display Ethernet activity and Ethernet/IP
bmon Display bandwidth captures
curl Used for file transfer
dhclient Analyze clients' IP address, gateway, DNS
dig Used for simple DNS lookup
dstat Collect and show system resources
ethtool Check settings of your NIC
ftp Used for file transfer
host Used for DNS lookup
hping3 Used for packet analysis
ifconfig Monitor and configure network interface
ip address Check network interfaces and routing
iptables Used for IP packet filtering
iftop Display current bandwidth usage
ifup Enable interfaces
ifdown Disable interfaces
iwconfig Monitor and configure wireless interfaces

Networking Commands

nload Used as a bandwidth monitoring tool
nmap Used for security audits
nslookup Used for DNS queries
ip route Routing table management
netstat Check network connections
route Display and manipulate IP routing table
ping Check reachability
sftp Secure file transfer
ss Give detailed information about sockets
ssh Used for secure connections
scp Secure file transfer
tcpdump Used for analyzing and capturing
telnet Used for classical unsecured connections
tshark Used for packet analysis and capturing
traceroute Used for path tracking
w Show who is logged in and what they do
wget Used to download content from servers
whois Check the WHOIS database and return IP and domain info

File Management

mkdir dir1 Create a new directory dir1
rmdir dir1 Remove an empty directory dir1
rm -r dir1 Remove a directory dir1
ln -s file1 link1 Create a symbolic link link1 to file1
chown user:group file1 Change the owner and group of file1
chmod 755 file1 Change permissions of file1 to 755
df -h Display disk space usage
du -sh dir1 Display the size of directory dir1
stat file1 Display detailed information about file1

User Management

adduser username Add a new user with username
deluser username Remove a user with username
passwd username Change the password for username
usermod -aG groupname username Add username to groupname
id username Display user ID and group ID for username
groups username Display group memberships for username
whoami Display the current logged-in username

Package Management

apt-get update Update the package lists
apt-get upgrade Upgrade all installed packages
apt-get install package Install a new package
apt-get remove package Remove an installed package
apt-get purge package Remove a package and its configuration
apt-get autoremove Remove automatically all packages
dpkg -i package.deb Install a package from a .deb file
dpkg -r package Remove an installed package

Disk Management

fdisk -l List disk partitions
mkfs -t ext4 /dev/sda1 Create an ext4 filesystem on /dev/sda1
mount /dev/sda1 /mnt Mount /dev/sda1 to /mnt
umount /mnt Unmount the filesystem mounted at /mnt
fsck /dev/sda1 Check and repair the filesystem on sda1
parted /dev/sda Partition a disk using GNU Parted
dd if=/dev/sda of=/dev/sdb Clone disk /dev/sda to /dev/sdb
lsblk List information about all available block devices

SSH and Remote Management

ssh user@hostname Connect to hostname as user
scp file1 user@hostname:/path Copy file1 to /path on hostname
rsync -avz file1 user@hostname:/path Synchronize file1 to /path on hostname
ssh-keygen Generate SSH key pairs
screen Start a screen session
tmux Start a tmux session
vncserver Start a VNC server session
ssh-copy-id user@hostname Copy SSH key to hostname for password-less login

System Monitoring

htop Interactive process viewer
free -h Display free and used memory
iostat Report CPU and I/O statistics
vmstat Report virtual memory statistics
sar Collect and report system activity info.
mpstat Report CPU usage
nmon Performance monitoring tool
uptime Display the system uptime

File Compression and Archiving

tar -cvf archive.tar dir1 Create a tarball of dir1
tar -xvf archive.tar Extract a tarball
tar -czvf archive.tar.gz dir1 Create a gzipped tarball of dir1
tar -xzvf archive.tar.gz Extract a gzipped tarball
gzip file Compress file
gunzip file.gz Decompress file.gz
zip archive.zip file1 file2 Create a zip archive of file1 and file2
unzip archive.zip Extract a zip archive

Text Processing

awk '{print $1}' file Print the first column of each line in file
sed 's/old/new/g' file Replace all occurrences of old with new
cut -d' ' -f1 file Cut the first field from each line in file
sort file Sort the contents of file
uniq file Remove duplicate lines from file
tr 'a-z' 'A-Z' < file Translate lowercase to uppercase in file
wc -l file Count the number of lines in file
split -l 1000 file Split file into chunks of 1000 lines each

What is Linux?

Linux is an open-source operating system kernel that serves as the foundation for various distributions, enabling users to manage hardware resources and run applications. Known for its stability and security, Linux is widely used in servers, desktops, and embedded systems around the world. Its flexibility and customization options make it a popular choice among developers and tech enthusiasts.

Is Linux an Operating System?

Yes, Linux is an operating system, specifically a Unix-like OS renowned for its robustness, flexibility, and security. It was developed by Linus Torvalds in 1991 and is built on the Linux kernel, which supports a wide variety of hardware platforms. Linux is open-source, meaning its source code is freely available for anyone to view, modify, and distribute. This open-source nature has fostered a vast community of developers who contribute to its continuous improvement, resulting in numerous Linux distributions (distros). Popular distros include Red Hat, Ubuntu, Fedora, Debian, and SUSE, each catering to different user needs and preferences.

For instance: Ubuntu is known for its user-friendly interface and is popular among desktop users and beginners, while Red Hat is widely used in enterprise environments for its stability and support. Fedora serves as a testing ground for new features that eventually make their way into Red Hat. Debian is valued for its stability and extensive software repositories, and SUSE is known for its excellent enterprise solutions and robust administrative tools. Linux powers a significant portion of the internet's infrastructure, including servers, supercomputers, and cloud environments. It is also prevalent in embedded systems, such as routers and smart devices, and has a growing presence on desktops. Its versatility, reliability, and cost-effectiveness make Linux a preferred choice for both personal and enterprise-level applications.

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Basic Linux Commands

Basic Linux commands are fundamental for anyone using the Linux operating system, whether for personal use, development, or system administration. These commands allow users to interact with the system, perform tasks, and manage files efficiently. Here are 17 examples of basic Linux commands:

Remove a directory: rmdir directory_name
Delete a directory: rm -r directory_name
Delete a file: rm file_name
Change a password: passwd username
Unzip files: unzip file.zip
Copy a directory: cp -r source_directory destination_directory
Add a user to a group: usermod -aG group_name username
Add a user: adduser username
Copy a file: cp source_file destination_file
List users: cut -d: -f1 /etc/passwd
Search for a file: find /path/to/search -name file_name
List user accounts: cat /etc/passwd
Perform a traceroute: traceroute hostname
Use grep to search within files: grep 'search_term' file_name
Create a user: useradd username
Create a file: touch file_name
Move a file: mv source_file destination_file

Understanding these basic commands is crucial for effectively managing and navigating a Linux system. They form the foundation for more advanced operations and scripts, making daily tasks more streamlined and efficient. By mastering these commands, users can enhance their productivity and proficiency in using Linux.

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