For a while now I've been using Byobu to manage screen sessions for me. However I've run into a strange issue: The session keeps locking. By locking I mean that I can't type anything, and only if I wait a few minuites does unlock and do everything I typed in before.

Currently its getting worse. The session keeps locking every minute or so. Even when I've restarted Putty, switched from Private Key auth to password auth, and even changed Putty installations, it still freezes. Its gotten to the point where I'll login and the current window is frozen but I'm able to switch to another window, only for that to freeze in a few seconds.

Another new development is that sometimes when I first login Byobu won't even come up, it will just sit there after the "Last login" line. One time I got a WriteMessage: Broken pipe error and it dropped to normal shell without byobu.

Strangely the tunnel's I've opened up still work. I was able to check the CPU graphs and saw that the server wasn't under any load, meaning that the session didn't freeze because it had other things to do.

Any suggestions on how to fix this?

  • Does it only happen on a particular server, from a particular client, or can you reproduce this on multiple machines? Are there clients from which this doesn't happen (on the same server)? What does the network look like between the client and the server? Do you have any problems scp'ing files? Does the session lock in the middle of typing, or only if you've been idle for a while? I wonder if you're running into an MTU issue or a broken NAT. Commented Jan 30, 2011 at 19:26
  • @In my limited testing this doesn't affect Linux clients but does affect Windows clients (still testing Ubuntu). The degradation has mainly happened on XP with 2 installations of Putty. With SCP I recently did have an issue of it not letting me connect until I completely disabled Byobu; however this was only one time. With freezing times, it locks up randomly: In the middle of typing or when I leave it alone (sometimes). And I only have this one CentOS server to test, so I'm not sure if it affects other machines. As I said I'm still testing if Byobu locks up in Ubuntu.
    – TheLQ
    Commented Jan 30, 2011 at 20:30
  • 1
    Can you type "ctrl-a : reset", or is even the screen escape key frozen?
    – user2267
    Commented Mar 26, 2011 at 15:54
  • @barry I never did try reset, although I don't think it work work as changing windows is also frozen.
    – TheLQ
    Commented Mar 26, 2011 at 17:01
  • Since you can still run commands on the machine when Byobu acts up, next time, investigate it. Run top to see if it's taking CPU time. Run strace -p1234 (where 1234 is the screen PID) to see what it's doing, and ditto for the SCREEN process. You'll need to be running a screen that's not setuid or setgid, or run strace as root. Commented May 19, 2011 at 20:41

2 Answers 2


Try this, it worked for me on putty:

  • Ctrl+Q - XON
  • Ctrl+S - XOFF
  • This issue hasn't come up recently so I can't test this. What does that do though?
    – TheLQ
    Commented May 19, 2011 at 15:14
  • 1
    @TheLQ: That's terminal flow control: Ctrl+S tells the terminal to stop sending stuff and Ctrl+Q tells it to send again. See also an example of where they're useful. Ctrl+Q comes last, by the way. I don't see why it would help here, but it's worth a try. Commented May 19, 2011 at 20:37
  • That wasn't it for me. Commented Feb 21, 2020 at 18:38

I've had this problem a couple of times. I've found that sending a SIGINT to the byobu process (kill -2 <byobu pid>) un-freezes the session. This worked when XON/XOFF did not work for me. After issuing the signal I can re-connect to the byobu shells and have normal function.

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