Read the scenario first
Each lab starts with a situation, the way a ticket or an exam question does. Work out what is being asked before you type anything.
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Linux DNS Troubleshooting Lab
A server reaches addresses but not names. Test with ping and dig, find the wrong name server and fix /etc/resolv.conf.
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Linux command line · Intermediate · About 12 minutes
The scenario
An application server can’t reach the company intranet at intranet.corp.example. The network team says the link is fine. Work through it in order: is the server on the network, can it reach its gateway, and can it turn a name into an address?
The network’s name server is 10.0.0.2.
A practice Ubuntu terminal that runs in your browser. It understands real commands, and nothing you type can break anything.
Your tasks
0 of 6 doneCheck the server’s own IP address. (not done yet)
Ping the default gateway, 10.0.0.1, to confirm the server is on the network. (not done yet)
Try to reach intranet.corp.example by name and read the error. (not done yet)
Find the name server this machine is using. (not done yet)
Point the machine at the right name server, 10.0.0.2. (not done yet)
Reach intranet.corp.example by name again to confirm the fix. (not done yet)
student@app01Practice 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
- Checking an address and route with ip
- Testing reachability with ping
- Testing name resolution with dig or nslookup
- Reading and correcting /etc/resolv.conf
Exams it helps with
- CompTIA Network+Domain: Network Troubleshooting
- CompTIA Linux+Domain: Troubleshooting
- CompTIA Server+Domain: Troubleshooting
Walkthrough
One way to complete the lab, with the reason for each step. Try it yourself first.
Show the worked solution
- 1Confirm the server has an address.
ip a - 2Confirm it can reach its gateway.
ping -c 4 10.0.0.1 - 3Try the name: it fails with “Temporary failure in name resolution”, so the network is fine and name lookups are not.
ping -c 2 intranet.corp.example - 4Look at the name server: 10.0.0.99 is not the network’s name server.
cat /etc/resolv.conf - 5Write the right one into the file.
echo "nameserver 10.0.0.2" | sudo tee /etc/resolv.conf - 6Test the name again.
ping -c 2 intranet.corp.example
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 Network+ (Network Troubleshooting), CompTIA Linux+ (Troubleshooting) and CompTIA Server+ (Troubleshooting).
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.
