🚀 Essential Linux Commands for DevOps Engineers

7 min readAug 29, 2024

1. File and Directory Operations

ls: List files and directories.

ls -l

Example: List all files and directories in the current directory with detailed information.

cd: Change directory.

cd /var/log

Example: Navigate to the /var/log directory.

cp: Copy files or directories.

cp file1.txt /backup/

Example: Copy file1.txt to the /backup/ directory.

mv: Move or rename files or directories.

mv file1.txt file2.txt

Example: Rename file1.txt to file2.txt.

rm: Remove files or directories.

rm -rf /tmp/*

Example: Forcefully remove all files in the /tmp/ directory.

mkdir: Create directories.

mkdir /myproject/logs

Example: Create a new directory logs inside /myproject.

touch: Create an empty file.

touch newfile.txt

Example: Create a new empty file named newfile.txt.

cat: Concatenate and display file content.

cat /etc/hosts

Example: Display the contents of the /etc/hosts file.

2. Process Management

ps: Display currently running processes.

ps aux | grep nginx

Example: List all processes related to nginx.

top: Display real-time system processes and resource usage.

top

Example: Monitor system processes and resource usage interactively.

kill: Terminate a process by PID.

kill 1234

Example: Terminate the process with PID 1234.

systemctl: Control system services (start, stop, restart).

systemctl restart nginx

Example: Restart the nginx service.

3. Networking

ip: Show/manipulate routing, devices, policy routing, and tunnels.

ip addr show

Example: Display all network interfaces and their IP addresses.

ping: Check connectivity to a remote server.

ping google.com

Example: Send ICMP echo requests to google.com.

curl: Transfer data from or to a server.

curl https://example.com

Example: Retrieve the content of https://example.com.

scp: Securely copy files between hosts.

scp file.txt user@remotehost:/path/to/destination

Example: Copy file.txt to a remote host under /path/to/destination.

4. Package Management

apt-get (Debian/Ubuntu): Install a package.

sudo apt-get install nginx

Example: Install the nginx web server.

yum (Red Hat/CentOS): Install a package.

sudo yum install httpd

Example: Install the httpd web server.

rpm: Install a package using RPM.

sudo rpm -ivh package.rpm

Example: Install a package from an RPM file.

5. Disk Usage

df: Display disk space usage.

df -h

Example: Show disk space usage in a human-readable format.

du: Estimate file space usage.

du -sh /var/log

Example: Display the total size of the /var/log directory.

6. Text Processing

grep: Search for patterns in files.

grep "error" /var/log/syslog

Example: Search for the term “error” in the /var/log/syslog file.

awk: Pattern scanning and processing language.

awk '{print $1}' file.txt

Example: Print the first column from file.txt.

sed: Stream editor for filtering and transforming text.

sed 's/oldtext/newtext/g' file.txt

Example: Replace all occurrences of oldtext with newtext in file.txt.

sort: Sort lines of text files.

sort file.txt

Example: Sort the lines in file.txt.

uniq: Report or omit repeated lines.

sort file.txt | uniq

Example: Remove duplicate lines from file.txt.

wc: Word, line, character, and byte count.

wc -l file.txt

Example: Count the number of lines in file.txt.

7. User Management

useradd: Create a new user.

sudo useradd devops

Example: Create a new user named devops.

usermod: Modify a user account.

sudo usermod -aG sudo devops

Example: Add the user devops to the sudo group.

passwd: Update a user's password.

sudo passwd devops

Example: Set or change the password for the devops user.

sudo: Execute a command as another user, typically the superuser.

sudo systemctl restart nginx

Example: Restart the nginx service as a superuser.

8. Compression

tar: Create or extract tar archives.

tar -cvf archive.tar /myproject/

Example: Create a tar archive of the /myproject/ directory.

tar -xvf archive.tar

Example: Extract the contents of archive.tar.

gzip: Compress a file using gzip.

gzip file.txt

Example: Compress file.txt using gzip.

gunzip: Decompress a file using gzip.

gunzip file.txt.gz

Example: Decompress file.txt.gz.

9. Version Control (Git)

git clone: Clone an existing repository.

git clone https://github.com/user/repo.git

Example: Clone the Git repository at the specified URL.

git status: Show the working tree status.

git status

Example: Display the current status of your Git repository.

git add: Add files to staging.

git add file.txt

Example: Add file.txt to the staging area.

git commit: Commit changes with a message.

git commit -m "Initial commit"

Example: Commit changes with the message “Initial commit.”

git push: Push changes to the remote repository.

git push origin main

Example: Push your commits to the main branch on the remote repository.

10. SSH and Remote Management

ssh: Log into a remote machine.

ssh user@hostname

Example: Connect to a remote host as the specified user.

ssh-keygen: Generate a new SSH key.

ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

Example: Generate a new SSH key pair.

ssh-copy-id: Copy your SSH key to a remote machine.

ssh-copy-id user@hostnam

Example: Copy your public SSH key to the remote host.

11. Monitoring and Logs

tail -f: Monitor logs in real-time.

tail -f /var/log/syslog

Example: Monitor the system log file in real-time.

dmesg: Display system message buffer.

dmesg | grep error

Example: Filter and display system messages related to errors.

journalctl: Query and display messages from the systemd journal.

journalctl -u nginx.service

Example: Display logs specific to the nginx service.

12. File Permissions and Ownership

chmod: Change file permissions.

chmod 755 script.sh

Example: Set the file script.sh to be executable by the owner and readable/executable by others.

chown: Change file ownership.

sudo chown user:usergroup file.txt

Example: Change the owner and group of file.txt to user and usergroup.

umask: Set default permissions for newly created files.

umask 022

Example: Set the default permissions for new files to 755.

13. Search and Find

find: Search for files and directories.

find /var/log -name "*.log"

Example: Find all .log files under /var/log.

locate: Quickly find files by name.

locate apache2.conf

Example: Locate the file apache2.conf on the system.

which: Locate a command's executable file location.

which python3

Example: Find the path to the python3 executable.

14. Advanced File Operations

rsync: Sync files and directories between two locations.

rsync -av /source/ /destination/

Example: Recursively sync files from /source/ to /destination/.

ln: Create symbolic or hard links.

ln -s /path/to/original /path/to/link

Example: Create a symbolic link to a file or directory.

diff: Compare files line by line.

diff file1.txt file2.txt

Example: Display differences between file1.txt and file2.txt.

tar -cvzf: Create a compressed archive.

tar -cvzf archive.tar.gz /myproject/

Example: Create a compressed tarball of the /myproject/ directory.

15. System Information

uname: Show system information.

uname -a

Example: Display all system information, including kernel version, hostname, and more.

uptime: Show how long the system has been running.

uptime

Example: Display the current time, how long the system has been up, number of users, and load average.

hostnamectl: Control and query the system hostname and related settings.

hostnamectl set-hostname new-hostname

Example: Set the system hostname to new-hostname.

free: Display memory usage.

free -h

Example: Show memory usage in a human-readable format.

lscpu: Display information about the CPU architecture.

lscpu

Example: Display detailed information about the CPU.

lsblk: List information about block devices.

lsblk

Example: Display all block devices, including their mount points.

df -h: Display disk space usage.

df -h

Example: Show the disk usage in a human-readable format.

du -sh: Show the total size of a directory.

du -sh /home/user/

Example: Display the total disk space used by /home/user/.

16. Networking Utilities

netstat: Network statistics.

netstat -tuln

Example: List all listening ports and their associated services.

traceroute: Trace the route packets take to a network host.

traceroute example.com

Example: Trace the path packets take to reach example.com.

dig: DNS lookup utility.

dig example.com

Example: Perform a DNS query for example.com.

nslookup: Query DNS to obtain domain name or IP address mapping.

nslookup example.com

Example: Query the DNS for example.com.

nmap: Network scanner.

nmap -sP 192.168.1.0/24

Example: Scan a network for active hosts.

iptables: Configure the Linux kernel firewall.

sudo iptables -L

Example: List all current iptables rules.

17. Advanced Text Processing

tr: Translate or delete characters.

echo "hello" | tr 'a-z' 'A-Z'

Example: Convert lowercase letters to uppercase.

cut: Remove sections from each line of files.

cut -d ':' -f 1 /etc/passwd

Example: Display only the first field from /etc/passwd.

paste: Merge lines of files.

paste file1.txt file2.txt

Example: Combine corresponding lines from file1.txt and file2.txt.

xargs: Build and execute command lines from standard input.

cat files.txt | xargs rm

Example: Read filenames from files.txt and remove them.

18. Job Management

jobs: List background jobs.

jobs

Example: Display all current background jobs.

bg: Resume a job in the background.

bg %1

Example: Resume the first job in the background.

fg: Bring a job to the foreground.

fg %1

Example: Bring the first job to the foreground.

nohup: Run a command immune to hangups.

nohup command &

Example: Run a command in the background, ignoring hangup signals.

19. System Performance

vmstat: Report virtual memory statistics.

vmstat 5

Example: Display system performance information every 5 seconds.

iostat: Report CPU and I/O statistics.

iostat -x 5

Example: Display extended I/O statistics every 5 seconds.

sar: Collect, report, or save system activity information.

sar -u 5

Example: Display CPU usage every 5 seconds.

20. Archiving and Backup

zip: Create a compressed archive.

zip -r archive.zip /myfolder/

Example: Create a ZIP archive of the /myfolder/ directory.

unzip: Extract files from a ZIP archive.

unzip archive.zip

Example: Extract the contents of archive.zip.

rsnapshot: File system snapshot utility for backups.

rsnapshot daily

Example: Perform a daily backup using rsnapshot (requires configuration).

These commands are foundational for managing Linux environments in DevOps practices, enabling efficient file operations, process management, networking, and more.