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When trying to connect to NX server with a NX CLient for Linux (installed from nxclient_3.5.0-7_amd64.deb) I get the following error.

NX> 203 NXSSH running with pid: 8009
NX> 285 Enabling check on switch command
NX> 285 Enabling skip of SSH config files
NX> 285 Setting the preferred NX options
NX> 200 Connected to address: nnn.nnn.nnn.nnn on port: 22
NX> 202 Authenticating user: nx
NX> 208 Using auth method: publickey
Received disconnect from nnn.nnn.nnn.nnn: 2: Too many authentication failures for nx

However when I am trying to use NX plugin for Remmina remote desktop client (from remmina-plugin-nx) I get the following different error:

NX> 536 ERROR: Reached the maximum number of allowed users on this server.

The Remmina diagnostic log states that it is NXSERVER - Version 3.5.0-11 - LFE. Is it a problem on my (client) side, or on server side?

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Knowing as much as nothing about NX, have you tried to Google that error? – grassroot Feb 13 '13 at 15:16

It turns out that I have hit the limit of NX Free Edition of NoMachine NX Server. According to NoMachine NX - Products Page the free edition of NX server is limited to maximum 2 concurrent connections and maximum 2 users.

The NX Licensing article does not explain how those 2 users are calculated, and it is only implied that it is automatically two users which logged in / used NX server first.

The nomachine sessions (nxserver) thread on Ubuntu Forums says that server session info is stored at /usr/NX/var/db. After examining those files it turns out that name of logged user is stored in session-info files there.

$ sudo grep -hR userName /usr/NX/var/db/* | sort | uniq

shows exactly two userNames.

I don't know why official NX Client for Linux has shown

Too many authentication failures for nx

as error, and it took using NX plugin for Remmina to get

NX> 536 ERROR: Reached the maximum number of allowed users on this server.


I turned to using X2Go which doesn't have those limitations, is quite easy to install on Ubuntu (just add PPA), uses NX 3.x, though it is compatible only with itself.

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