While remotely connecting to a Linux machine using ssh, my .ksh session hangs after being inactive for sometime. If I try to type or ctrl-z, the prompt does not respond. Is there a way to restore my session?
Asked
Active
Viewed 155 times
2
-
It's not immediately clear if your shell is hung, or if you've lost your ssh session to your shell. Are you trying to troubleshoot this apparent hang, or for ways to maintain a remote session if/when your (ssh) connection drops? – Jeff Schaller May 24 '16 at 17:28
-
I login to an ssh session in shell 1, switch to shell 2 to do some piece of work there, come back to shell 1 after 15-20 mins and can't type anything in shell 1. I wish to maintain the remote connection in shell 1. – Plebeian May 24 '16 at 17:45
-
Not sure if shell 1 times out or drops the connection or is hung. – Plebeian May 24 '16 at 17:46
-
It sounds to me like you've lost your ssh connection. No characters show up in shell 1, and you haven't been returned to your pre-ssh prompt? – Jeff Schaller May 24 '16 at 17:47
-
Is there a way to estore and continue the session in shell 1 ? – Plebeian May 24 '16 at 17:50
-
Read restore in my previous comment. – Plebeian May 24 '16 at 17:51
-
How do I return to my pre-ssh prompt? – Plebeian May 24 '16 at 17:59
-
If the remote side hasn't closed the ssh connection, then use shell 2 to kill shell 1's ssh process. Does your remote shell have a TMOUT variable set? – Jeff Schaller May 24 '16 at 18:09
-
No. How can I find out about TMOUT? – Plebeian May 24 '16 at 18:16
-
ssh back in and run: echo $TMOUT – Jeff Schaller May 24 '16 at 18:17
-
Ran echo $TMOUT. Output is 0. – Plebeian May 24 '16 at 18:22
1 Answers
0
What's probably happening is that some network equipment somewhere between the client and the server terminates connections that have been idle for a certain time. Such network equipment (firewalls, NAT appliances, …) often kills idle connections after a while to save memory (it's a defense against denial of service, but it does tend to be an annoyance to users).
To avoid this, you can set the ServerAliveInterval option in ~/.ssh/config to a value that's lower than the timeout after which your connections get killed. For example, if your connections get killed when they've been idle for 10 minutes, set ServerAliveInterval to 5 minutes:
ServerAliveInterval 300
Additionally, in case you do get cut off, use a terminal multiplexer on the server: Screen or tmux. For example, with Screen, run screen -rd on the server when you log in; if you get disconnected, reconnect to the server and run screen -rd to reattach to your existing session. See also and tmux vs. GNU Screen
Gilles 'SO- stop being evil'
- 829,060