Servers run Linux. Containers run Linux. CI runners run Linux. If you want to do DevOps, you need to be comfortable at the Linux command line. Let’s get you there.

Tip: On Windows? Install WSL2. On macOS? The Terminal is already Unix-based. Otherwise, spin up an Ubuntu virtual machine.

Getting around the filesystem

pwd             # print working directory (where am I?)
ls              # list files
ls -lah         # list with details, including hidden files
cd /etc         # change directory
cd ~            # go to your home directory
cd ..           # go up one level

Working with files and folders

mkdir projects          # create a directory
touch notes.txt         # create an empty file
cp notes.txt backup.txt # copy
mv backup.txt old.txt   # move or rename
rm old.txt              # delete a file
rm -r projects          # delete a directory and its contents

Reading and editing files

cat file.txt        # print the whole file
less file.txt       # scroll through a large file (q to quit)
head -n 20 file.txt # first 20 lines
tail -n 20 file.txt # last 20 lines
tail -f app.log     # follow a log in real time
nano file.txt       # simple terminal editor

Permissions (the part that trips everyone up)

Every file has an owner, a group, and permissions for read (r), write (w), and execute (x).

ls -l script.sh
# -rwxr-xr-- 1 user group 0 Jan 1 12:00 script.sh

chmod +x script.sh   # make a file executable
chmod 644 file.txt   # owner read/write, others read
chown user:group f   # change ownership

Quick guide to the numbers: 4 = read, 2 = write, 1 = execute. Add them up per group (owner/group/others). So 755 = rwxr-xr-x.

Processes

ps aux              # list running processes
top                 # live process view (q to quit)
kill 1234           # stop process with PID 1234
kill -9 1234        # force kill

Networking basics

ping google.com         # check connectivity
curl https://api.io     # make an HTTP request
curl -I https://site    # headers only
ss -tulpn               # list listening ports

Package management (Ubuntu/Debian)

sudo apt update             # refresh package lists
sudo apt install nginx      # install a package
sudo apt remove nginx       # remove a package

Piping and redirection

This is where the shell gets powerful, you chain commands together:

cat access.log | grep "404" | wc -l   # count 404s in a log
ls -l > files.txt                      # write output to a file
echo "hello" >> notes.txt              # append to a file

Practice challenge 🏋️

Try this end to end:

  1. Create a folder called devops-practice.
  2. Inside it, create a file hello.sh containing echo "Hello DevOps".
  3. Make it executable and run it with ./hello.sh.
mkdir devops-practice
cd devops-practice
echo 'echo "Hello DevOps"' > hello.sh
chmod +x hello.sh
./hello.sh

If you saw Hello DevOps printed, congrats, you just wrote and ran your first script. 🎉

What’s next?

You can move around Linux now. Time to learn how teams track and share code.

👉 Next up: Git & GitHub Crash Course