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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.

bensatlantic
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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? – FelixJN 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

2 Answers2

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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 Ctrl + S, (which stops output to the terminal) and the fix for that is to type Ctrl+Q (resume output).

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

Further reading:

Error404
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Thomas Dickey
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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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If it is a gnome-terminal: Possibly the "read-only" mode is toggled. Right click anywhere in the input/output panel, and unselect "read-only" (by clicking on it) in the pop-up context menu to release the terminal from the frozen state.

Robin Hsu
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