SSH – Why Starting Firefox in VM Opens on Host Machine?

firefoxssh

I have a SLED 10 host machine and I am using a SLES 10 VM via ssh -X.

When I start firefox in my VM using firefox & then it runs the firefox which is installed in the VM. So that's fine.

However, if my host machine's firefox is running, and then I start VM's firefox, then instead of starting its own, a new session of host's firefox starts running.

Same happens the opposite way also, if VM's firefox is running then I am not able to start host's firefox.

Best Answer

Because for some reason, the firefox devs have decided that is a good idea. In fact, they are so sure this is a feature and not a bug, they have even provided an option to disable it. Try running

firefox -no-remote

That should cause a new instance to be started on the remote machine. For (a tiny bit of) more info, try firefox -h:

-no-remote         Do not accept or send remote commands; implies -new-instance.
-new-instance      Open new instance, not a new window in running instance.

This had me completely baffled for a while and I still don't understand why (or, for that matter, how) they do this.

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SSH OpenSSH – How to Start a Specific Shell and Run Commands Remotely

The most obvious way to run a command remotely is to specify it on the ssh command line. The ssh command is always interpreted by the remote user's shell.

ssh bob@example.com '. ~/.profile; command_that_needs_environment_variables'
ssh -t bob@example.com '. ~/.profile; exec zsh'

Shared accounts are generally a bad idea; if at all possible, get separate accounts for every user. If you're stuck with a shared account, you can make an alias:

ssh -t shared-account@example.com 'HOME=~/bob; . ~/.profile; exec zsh'

If you use public key authentication (again, recommended), you can define per-key commands in ~/.ssh/authorized_keys. See this answer for more explanations. Edit the line for your key in ~/.ssh/authorized_keys on the server (all on one line):

command="HOME=$HOME/bob;
     if [ -n \"$SSH_ORIGINAL_COMMAND\" ]; then
       eval \"$SSH_ORIGINAL_COMMAND\";
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Ssh – “channel 3: open failed: administratively prohibited: open failed” when creating a VNC session on a SSH tunnel

The option you are looking for is not AllowTunnel (it is for VPN and level 3 forwarding using tun devices). You are looking for AllowTcpForwarding, which handles local and remote port forwarding of TCP traffic in ssh.

Have a look what values is in your server and change it to yes:

AllowTcpForwarding yes

Best Answer

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