mjhjmtu

I've a problem with port forwarding command using sshpass.
Problem is that it's working on one server and does not work on another.
Both are Debian 7 x64 boxes.

sshpass -p password ssh -f -D 0.0.0.0:2002 -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o LogLevel=debug root@5.5.5.5 -T -N

This command works with no problems on server 1 but does not work on server 2.

Debug output from failing server:

Authenticated to 5.5.5.5 ([5.5.5.5]:22).
debug1: Local connections to 0.0.0.0:2002 forwarded to remote address socks:0
debug1: Local forwarding listening on 0.0.0.0 port 2002.
debug1: channel 0: new [port listener]
debug1: forking to background

Debug output from working server:

Authenticated to 5.5.5.5 ([5.5.5.5]:22).
debug1: Local connections to 0.0.0.0:2002 forwarded to remote address socks:0
debug1: Local forwarding listening on 0.0.0.0 port 2002.
debug1: channel 0: new [port listener]
debug1: forking to background
debug1: Entering interactive session.

Sshpass and ssh binaries are equal on both servers. I've checked this using md5sum.

Does anyone have an idea what could be wrong? I'm losing my mind trying to solve this mystery.

TL;DR


This worked for me:

sshpass -p password nohup ssh -f ... >/dev/null

Well, I almost lost my mind too.

The difference between your debian hosts that causes sshpass to either work or not is the number of CPU cores. The issue appears on a single-core host. Playing with strace showed that sshpass process is killed by the system after receiving SIGHUP. On a multi-core host, the forked ssh process has enough time to setup SIGHUP handler so it's not killed.

As a workaround you can use nohup utility to run sshpass so it's not killed by SIGHUP.