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Linux SSH Hardening Lab
Harden an SSH server’s configuration: turn off root login and password sign-in with sed, then restart the service.
Last updated
Linux command line · Intermediate · About 10 minutes
The scenario
An audit flagged the SSH configuration on db01: root can sign in directly, and passwords are accepted, so the server is open to password guessing. Every administrator already signs in with a key.
Change the two settings in /etc/ssh/sshd_config and restart the service so they take effect. The practice terminal has no text editor, so make the changes with sed.
A practice Ubuntu terminal that runs in your browser. It understands real commands, and nothing you type can break anything.
Your tasks
0 of 4 doneShow the current values of PermitRootLogin and PasswordAuthentication. (not done yet)
Set PermitRootLogin to no. (not done yet)
Set PasswordAuthentication to no. (not done yet)
Restart the SSH service so the new settings are read. (not done yet)
student@db01Practice terminal · simulated
Practice terminal: real commands on a simulated Ubuntu server. Type help to see what it knows.
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About this lab
What you’ll practice, and where it’s tested
What you’ll practice
- Finding settings in a file with grep
- Changing a line in place with sed -i
- Restarting a service so a new configuration is read
Exams it helps with
- CompTIA Security+Domain: Security Operations
- CompTIA Linux+Domain: Security
- CompTIA Server+Domain: Security and Disaster Recovery
Free performance-based questions: Security+, Linux+, Server+
Walkthrough
One way to complete the lab, with the reason for each step. Try it yourself first.
Show the worked solution
- 1See the two settings as they are.
grep -E "PermitRootLogin|PasswordAuthentication" /etc/ssh/sshd_config - 2Turn off root login.
sudo sed -i 's/^PermitRootLogin yes/PermitRootLogin no/' /etc/ssh/sshd_config - 3Turn off password sign-in.
sudo sed -i 's/^PasswordAuthentication yes/PasswordAuthentication no/' /etc/ssh/sshd_config - 4Restart the service.
sudo systemctl restart ssh
Guide
How to get the most from a lab
Type the commands yourself
Typing a command, getting it wrong and fixing it is what makes it stick. Use the hints when you’re stuck, not before.
Check the walkthrough afterwards
Every lab has a worked solution with the reason for each step. Read it even when you finished: there is often a shorter way.
Do it again from memory
Reset the lab a day later and do it without hints. If you can, you know it. If you can’t, you’ve found what to study.
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FAQs
Got Questions? We’ve Got Answers.
Find quick answers or contact our support team.
Is this a real Linux machine?
No. It’s a practice terminal that runs in your browser. It understands the real commands the lab needs, and many more, and it answers the way an Ubuntu server would. It isn’t a full operating system: nothing is installed, and nothing you type can break anything.
Which commands does the practice terminal understand?
The everyday ones: ls, cd, cat, grep, awk, sed, sort, uniq, find, chmod, chown, useradd, usermod, passwd, systemctl, journalctl, ip, ping, dig, ss and ufw, with pipes, redirects and sudo. Type help in the terminal for the full list. Text editors and package installs aren’t included.
Which exams does this lab help with?
It practices skills from CompTIA Security+ (Security Operations), CompTIA Linux+ (Security) and CompTIA Server+ (Security and Disaster Recovery).
Do I need an account?
No. The labs run in your browser and nothing is saved. Sign up only if you want OpenpassAI’s full labs and progress tracking.
