Module 14 · When Something Goes Wrong
Every computer breaks sometimes. That's not a disaster — it's normal. Windows breaks. Macs break. Linux breaks. The difference between someone who panics and someone who calmly fixes it is just knowing what to try, in what order. This module gives you that order.
By the end of this module, you will:
- Know the six things to try, in order, when anything stops working
- Recognise the four most common Linux error messages and what they really mean
- Know where to find help (and how to ask for it well)
- Stop being scared of error messages — they're usually friendly once you read them
Good news, before we start
Linux error messages are usually friendly. They tell you what went wrong in plain words. Compare to Windows, where you sometimes get "0x8024A105" with no clue what it means — Linux nearly always says something more like "no space left on device" or "permission denied". So the first rule of fixing Linux problems is the easiest rule of all: read the error message. It's usually telling you the answer.
The Golden Rule: read the error message
If you do nothing else, do this. Read the error message before reacting. On Linux, the message is usually telling you exactly what is wrong. Examples that have shipped in real systems for years:
| If you see | It almost always means |
|---|---|
| "No space left on device" | Your hard drive is full. Delete something. |
| "Permission denied" | You are not allowed to do this. Try the same command with the word sudo in front (which means "do this as the boss"). |
| "No such file or directory" | The file you mentioned is not where you said it is. Check the spelling. Check the folder. |
| "Command not found" | The program you tried is not installed (or you typed its name wrong). Search Ubuntu Software for it. |
Notice that none of those are mysterious. Read what the screen says, do the obvious thing, and most of the time it works.
The six things to try, in order
When something on Linux stops working and you do not know why, walk through these six checks. They sound simple — that is because they are. Most problems get fixed somewhere in the first three steps.
Read the error message
If there is a message on screen, read it slowly, all the way through. Do not skim. Do not immediately Google. Linux's errors usually tell you what is wrong in plain words.
Is the disk full?
A surprising number of "weird" Linux problems are just a full hard drive. Open the Files app and look at how much space is used. Or, in the terminal, type df -h — that shows you. If anything is above 90%, that is almost certainly the problem. Empty Trash, delete old downloads, free up space.
Have you turned it off and on again?
Yes, really. Linux is more stable than Windows so people are sometimes too proud to reboot. But a fresh restart fixes a huge percentage of weird issues — Bluetooth glitches, frozen apps, network gone funny. Restart first, then keep troubleshooting if the problem comes back.
Did you change something just before it broke?
Did you install a new app yesterday? Did you change a setting? Did you plug in new hardware? The thing you changed most recently is almost always the cause. Try undoing it.
Run "Software Updater"
Search "Software Updater" in your Activities, run it, install whatever it offers. A surprising number of problems are bugs that have already been fixed in an update you have not installed yet. Same idea as Windows Update.
Search the exact error message online
Copy the exact words of the error message. Paste them into Google. Do not paraphrase. The exact wording is what helps you find someone who hit the same problem. Add your distro name (e.g. "Ubuntu") to the search. You are almost certainly not the first person to see this — and there is almost certainly an answer already written.
The "have you tried turning it off and on again?" rule
It is a joke for a reason. About a third of all Linux problems — frozen apps, weird screen flickers, Bluetooth gone silent, sound disappeared — are fixed by a simple restart. Do not be too proud. Restart, then carry on troubleshooting only if it does not come back.
Where to find help
Even people who have used Linux for 20 years search for answers every single day. That is not a sign of weakness — it is how Linux works. Here is where to look, in order of usefulness:
- The exact error message in Google — copy and paste, add your distro name. 90% of the time you will find the answer in the first three results.
- Ask Ubuntu (askubuntu.com) — community Q&A specifically for Ubuntu. Massive archive. Search before posting; almost always already answered.
- The Ubuntu Forum (ubuntuforums.org) — older but still extremely active.
- Reddit r/linuxquestions and r/ubuntu — friendly, beginner-tolerant. People will help.
- The Mint forum, the Fedora forum, etc. — if you are using a different distro, every distro has its own forum and they are all welcoming.
How to ask for help so people answer
Three things make people want to help:
- Say what you tried. "I tried X, Y, Z" — shows you have already done some thinking.
- Paste the exact error. Not a paraphrase, not a screenshot of your phone showing the screen — the actual text.
- Say which distro and which version. "Ubuntu 24.04" tells the helper a lot.
"It does not work, what do I do?" gets ignored. "I'm on Ubuntu 24.04, when I try to print I get the message X, I've tried restarting and reinstalling the printer driver" gets answered in five minutes.
If your computer will not boot at all
This is the only properly scary one. You turn the laptop on, and instead of getting to your normal desktop, you see a black screen, or a strange menu, or a wall of text. Do not reinstall. Almost every boot problem has a fix that is quicker than reinstalling.
| What you see | What to try |
|---|---|
| Black screen, then nothing | Hold down the power button to force off. Try again. If still bad, restart your computer holding the Shift key — that opens a hidden menu called "GRUB" with rescue options. |
| Forgot your password | From the GRUB menu (hold Shift on boot), pick "Recovery mode". You can reset your password from there. |
| Linux just got really slow after an update | Boot into Recovery mode, run the "repair" option. Or restart and pick the older kernel from the GRUB menu. |
| Stuck somewhere weird | Press Ctrl+Alt+F2 — you get a hidden text screen where you can type, even when the desktop is frozen. Often saves the day. |
For curious readers: the technical commands behind the six steps
If you are comfortable in the terminal already, here are the actual commands the six-step sequence translates to. You do not need these on day one — they are the technician's version of the same six checks.
- Read the error:
journalctl -xeshows the most recent system errors with extra context.journalctl -u servicename -n 50shows the last 50 messages from a specific service. - Disk space:
df -h(overall),du -sh /var/log/*(find what is taking up the space). - Memory:
free -h. If swap is near full, the system is starved of RAM. - Failed services:
systemctl --failedlists everything broken. Restart withsudo systemctl restart servicename. - Hardware:
lspcilists cards on the motherboard,lsusblists USB devices,ip linklists network interfaces. - Boot rescue: at GRUB, press e, append
nomodesetto the line starting withlinux, press Ctrl+X. Boots with safe-mode graphics so you can fix a broken NVIDIA driver.
You will meet most of these properly in Modules 11 (system monitoring), 12 (networking), and 17 (security). Do not worry about memorising any of them now.