SSH Update Breaks NX Server

If you use NoMachine’s very cool NX server to access a linux system remotely, and you installed the open-ssh update for the broken random number generator problem this morning, then you may have run into a situation where the update breaks NX server. The problem is that the local host’s RSA key is stored in a file used by NX Server, and when that key was regenerated it no longer matched.

The NX list of permitted host keys is stored in /usr/NX/home/nx/.ssh/known_hosts (at least it is on debian). You should see two identical entries, one for localhost and one for If your NX Server install is more complicated than mine your mileage may vary. Your shiny new RSA host key is located in /etc/ssh/ Replace the key value in known_hosts with the new key value for both entries, and you should be all set.

Note that running /usr/NX/bin/nxserver –update might also fix it, or one of the other commands might. I didn’t experiment beyond trying nxserver –history clear, which did not do it for me.

2 thoughts on “SSH Update Breaks NX Server

  1. Mark,

    I to found that NX was broken after the SSH upgrade on my Kubuntu 8.04 distribution. I’m using FreeNX (unlimited connections) and found that your instructions didn’t work for me. I found the known_hosts file is in /var/lib/nxserver/home/.ssh and I tried to replace the key in there with the new key from /etc/ssh but I continually got errors that NX wasn’t installed or running.
    So, I ran nxsetup –install –clean –setup-nomachine-key –purge
    This regenerated the keys and installed them and pretty much gave me a new nx environment which now works just like it used to.
    Thought I’d pass this on for your consumption.

    — Kevin

  2. Thanks for the information, Kevin. It’s good to have a solution on file that doesn’t involve hand-editing the configuration files.

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