On several of my clusters I am seeing a problem with ssh and scp hanging on exit. Here's an example: root@uinta ~ # scp /etc/ssh/ssh_known_hosts node0000:/etc/ssh ssh_known_hosts 100% 633KB 632.5KB/s 00:00 [program just hangs here] Meanwhile, on node0000 (with some editing for brevity): -bash-3.00# ps -ef UID PID PPID C STIME TTY TIME CMD root 1613 976 0 10:12 ? 00:00:00 sshd: root@notty root 1617 1613 0 10:12 ? 00:00:00 [scp] <defunct> If I kill the sshd process (1613) then things continue normally on uinta. If I CTRL-C the scp process on uinta then I am left with a defunct process and the sshd process it is connected to on node0000. The hang rate for these scp attempts is roughly 50%, in a random fashion. Looking for another way to skin the cat I have tried: root@uinta /etc/ssh # cat /etc/ssh/ssh_known_hosts | ssh -f -n node0000 'cat > /etc/ssh/ssh_known_hosts' This give me a much lower failure rate, ~1%, but eventually it hangs and on node0000 we see: -bash-3.00# ps -ef UID PID PPID C STIME TTY TIME CMD root 1647 976 0 10:19 ? 00:00:00 sshd: root@notty root 1651 1647 0 10:19 ? 00:00:00 [bash] <defunct> Following what advice I could google up I've added shopt -s huponexit to .bashrc and .bash_profile. This seems to have increased the successful connection/disconnection rate a little, up to the 50% mentioned above. Prior to this it almost always hung on this particular cluster. Any suggestions or tips whould be greatly appreciated. Thanks, jbh