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Old 05-02-2004, 10:05 PM   #1
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Telnet/SSH screen stops responding after a while but the session is still active

The system is Redhat 9. I just did a RPM update using the Check4Update utility included with Redhat distributions, which upgraded my kernel from 2.4.20-30.9 to 2.4.20-31.9, together with a bunch of other RPM's. I have done this many times and no problems so far.

Everything went okay with this update, except one problem I just noticed. When I telent or SSH to the server and leave the session idle for a while, the screen will stop responding to my typings. In other words, if I don't do anything for a couple of minutes and start to type again, the curson won't move and the whole screen just freezes. I have to close the window and reconnect again.
However, I know the session is still active when the screen freezes. The reason I know this is that I used the "screen" command when I telnet/SSH over, and when I reconnect to the server after the screen freezes, I can pickup my previous "virtual screen" by using the "screen -r" command. And when I resume the previous "virtual screen" by doing so, I saw all the text I typed when the screen freezes.

So the whole problem looks like this: in my telnet or SSH session, if I leave it idle for a couple of minutes and start to type again, the text I typed is sent over to the server, however, the server didn't send the respond back to my telnet / SSH client and therefore, makes the client window looks frozen.

Does anyone know what might be the cause? And unfortunately, I don't have the list of RPM's that was just updated.

Thank you!
Old 05-03-2004, 01:36 PM   #2
Registered: Mar 2003
Location: Scotland
Distribution: Slackware, RedHat, Debian
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Welcome to LQ.

This usually happens when there is a break in your network connection or you have a timeout value set for one of your services. SSH has very good keepalive options that you can set in sshd_config. For a complete list of options:
man sshd_config
Old 05-03-2004, 07:08 PM   #3
Registered: Oct 2003
Distribution: Slackware
Posts: 388

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You don't say if this is on a LAN or across the internet.
Is the connection passing though a NAT router/connection sharing system/ICS/ipmasq/whatever-you-call it?

NAT devices usually drop idle connections after some time.
Old 05-03-2004, 11:21 PM   #4
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sorry for the late reply, I was suprised to discover that my box was total dead after it stopped responding in the middle of the day. After experiencing all kinds of wierd things during my troubleshoot, I discovered that one of the memory dimm turned bad. It basically corruptted the filesystem and made the system non-bootable.

Now I am backing up data and need to reinstall the system
Old 05-04-2004, 12:52 PM   #5
Registered: Mar 2003
Location: Scotland
Distribution: Slackware, RedHat, Debian
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You possibly already know but if you want a good memory test then try memtest86 or memtest86+


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