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What is the most probable cause of terminal freeze / unresponsive keys? I'm a relatively new Linux user (2 yrs) and am still learning to use the command line. I have used xkill and similar commands to clear a stuck process, but in some cases the keys simply don't respond and I've reverted to pulling the battery due to impatience. My question is - if the keys on the terminal are unresponsive then is it because there are processes still working, unseen by me, that have not finished? If I can't use my keyboard, then I'm unable to execute ANY command. Were I to be patient and let the software complete its tasks, would I at some point regain access to the keyboard? Or are there situations where I can never regain active keys without a reboot? Thanks.

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    There is not really enough information to answer your question. For example, does just one terminal window become frozen, or the whole desktop? Do non-keyboard activities (mouse, etc.) continue to work? Can you log in from somewhere else when this happens? What application is running when this happens? It's worth noting that non-full-screen non-curses applications running on the terminal won't prevent your keypresses from showing up, because the kernel continues to do cooked mode terminal input processing, so even hung applications in a terminal won't usually cause the effect you're describing – Celada Feb 21 '16 at 14:33
  • Do you start a (heavy) process in these cases? Can you cancel it via CTRL+C? What commands are we talking? Does it happen randomly, even without you putting in commands? – Fiximan Feb 21 '16 at 15:44
  • Sorry - first timer here. I'll try to be more specific. Last time this happened, I was interacting with the GUI (Linux Mint) from the command line, learning to use nemo to open applications. I surely had several processes going including error messages. The terminal locked up and my first reaction is CTRL+C, but terminal does not respond, nor mouse because I'm stuck in terminal. Also, power button doesn't respond. I know the cause is me - too many commands - but question is - will the system recover through waiting? Right or wrong, I'm deliberately pushing the system to learn results. – bensatlantic Feb 22 '16 at 13:38
  • I believe I caused my last few terminal freezes through trying to learn how to open applications from the terminal rather than the GUI - I've learned how to do this since my last post. Still interested though as to whether a freeze is permanent - for ex - does the terminal buffer get filled and lag behind - if so, I imagine that it would clear. But most freezes that can't be fixed with Ctrl C / S or Q seem to lock me up permanently. Thanks guys. – bensatlantic Feb 26 '16 at 21:46
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If a terminal is frozen but not the rest of the GUI, then the first place to check is if you typed controlS, (which stops output to the terminal) and the fix for that is to type controlQ (resume output).

Because OP explicitly said "terminal", however, there is no reason to suspect the GUI.

Further reading:

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  • Thanks - I will write this down and apply next time. In most cases when this happens, it's due to trying too many things too quickly on my part. Appreciate the response. – bensatlantic Feb 22 '16 at 13:41

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