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System Monitor shows what the computer is doing now. It fills some of the same role as Windows Task Manager, including viewing resource use and responding to an application that has stopped.
It also lists system work you did not start directly. Do not end an unfamiliar item merely because its name looks technical.
Read four resource types
Open System Monitor from the application search. Its exact tabs and charts can vary, but the main measurements are:
- CPU: processor work. A brief rise while an application opens can be normal.
- Memory: working space used by open programs and the operating system. Linux also uses available memory for useful caching.
- Disk: stored capacity and, in some views, activity reading or writing data.
- Network: data moving through Wi-Fi, Ethernet, or another connection.
A high number is evidence, not a diagnosis by itself. Ask what task the computer is currently performing.
Application and process are related
A process is a running instance of a program or system service. One graphical application can create several processes.
A browser, for example, may separate tabs or extensions. Ending one unfamiliar browser process can affect a different tab than expected.
Use the visible application name and what happened just before the freeze. Do not assume the highest process in the list is automatically faulty.
Try the normal close first
When an application looks frozen:
- Wait briefly. It may be opening a large file or finishing a save.
- Try its ordinary Close action once.
- Look for a save or confirmation dialog behind another window.
- Switch to another application to see whether the whole desktop or only one app is affected.
Repeated clicking can queue more work and make a busy application look worse.
Use End Process only when needed
If the application remains unresponsive, open System Monitor and locate the matching process. Select it and choose End Process.
According to GNOME System Monitor help, End Process first asks the process to close, giving it an opportunity to finish more cleanly.
Wait a few seconds. Confirm that the application’s windows close and the process disappears.
Read high CPU without panicking
Sort processes by CPU use when the computer feels busy. Observe for more than one instant.
Short peaks can come from opening an app, loading a page, compressing a file, installing updates, or drawing the desktop. A process that stays unusually high while idle is more useful evidence.
For memory, look at whether the system is actually slowing or reporting pressure. A large application using memory while doing expected work is different from an unknown process growing continuously.
If the computer feels slow
Check in this order:
- Is an update, file copy, browser download, or other expected task active?
- Is one application visibly unresponsive?
- Does System Monitor show sustained resource use from an identifiable process?
- Is free disk space very low?
- Does the problem remain after saving work and restarting normally?
Do not end a process named only because it uses memory. Background system processes are part of a working desktop.
Common mistakes
Force-ending before waiting. Give an application a short chance to finish a heavy task.
Clicking the frozen window many times. One close request and a pause provide clearer evidence.
Ending the first high-CPU process. Identify the name, task, and sustained behavior.
Using Kill before End Process. Start with the less forceful option.
Assuming high memory is always a leak. Consider the application and whether the system is actually impaired.
Forgetting unsaved work in other windows of the same application. One process action can affect several windows.
Practice
Knowledge check
Choose the safest way to close the app.
A text editor stopped responding while a large file opened, but the rest of Ubuntu works. Put waiting, normal close, End Process, and Kill in order. State the risk before the final action.
What to learn next
Continue to Ubuntu Desktop Troubleshooting for Beginners for symptom-led checks that stay graphical.