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| − | NX is [[software]] for a [[terminal server]]. It allows you to [[control a computer via the network]] graphicall. NX is faster than [[vNc]]. One implementation is [[freeNX]].
| + | CPUWatch completely paeuss processes until the load decreases, so its not ideal for services like httpd which would completely drop off the map if they were effectively paused . It's moreso handy for cron style processes which need to be ran at intervals such as backups or other sundry tasks.Hope this helps and thanks for reading Victor! |
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| − | = Concept =
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| − | For NX, a user called ''nx'' must exist on the server and this user must allow [[passwordless login]]. The user must also have ''nxserver'' as default shell in /etc/passwd. The client has they key that is authorized and can therefore start commands in the nxserver shell on the server. After connecting the NX user via ssh, the user for the session is authenticated.
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| − | = Install NX as display manager =
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| − | Maybe you have a very old computer and want to make it a [http://en.wikipedia.org/wiki/Thin_client thin client] to a faster one (the faster one acting as [[terminal server]]). Then you want the old computer to display the NX client program right after startup, without a user having to log in. So you want [[Nx]] to be your display manager. Here are some changes I did to /etc/init.d/xdm to make this happen:
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| − | case "$1" in
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| − | start)
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| − | X &
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| − | export DISPLAY=:0
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| − | /usr/NX/bin/nxclient
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| − | [[scripting tutorial|while]] true; do [[sleep]] 9; done
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| − | | |
| − | = TroubleShooting =
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| − | To get logging output to /var/log/messages, edit /usr/NX/etc/node.cfg. Set
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| − | SessionLogLevel = "6"
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| − | and you can read NX' log from /var/log/messages. Let's look at this one:
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| − | <pre>
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| − | Jan 8 17:07:18 mars NXNODE-3.2.0-11[30374]: ERROR: run command: process: 30461 died because of signal: 9 Logger::log nxnode 3844
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| − | Jan 8 17:07:18 mars NXNODE-3.2.0-11[30480]: Directory '/home/tstaerk/.nx/C-mars-1019-7C3118AB902BD0DFE9CEC4AC7631B407' renamed into '/home/user/.nx/F-C-mars-1019-7C3118AB902BD0DFE9CEC4AC7631B407' for further investigation Logger::log nxnode 6215
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| − | </pre>
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| − | Now you [[cd]] to /home/user/.nx/F-C-mars-1019-7C3118AB902BD0DFE9CEC4AC7631B407 and look at the log files.
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| − | == no version information available ==
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| − | ;Symptom: nxclient won't start but output
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| − | # /usr/NX/bin/nxclient --wizard
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| − | /usr/NX/bin/nxclient: /usr/NX/lib/libz.so.1: no version information available (required by /usr/lib64/libpng16.so.16)
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| − | /usr/NX/bin/nxclient: relocation error: /usr/lib64/libpng16.so.16: symbol inflateReset2, version ZLIB_1.2.3.4 not defined in file libz.so.1 with link time reference
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| − | ; Reason: libpng requires version information from libz and does not get it. For more information call ldd /usr/NX/bin/nxclient:
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| − | # ldd /usr/NX/bin/nxclient
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| − | /usr/NX/bin/nxclient: /usr/NX/lib/libz.so.1: no version information available (required by /usr/lib64/libpng16.so.16)
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| − | [...]
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| − | ;Solution: Overwrite nxclient's z library with the system's:
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| − | mv /lib/libz.so.1 /usr/NX/lib/libz.so.1
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| − | Kim!You are amazing! I would love to set up a fialmy session for this May or June if you have availability. Please just let me know. Again, you are amazing and take beautiful pictures.
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| − | | |
| − | == The NX service is not available ==
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| − | ;Symptom: When logging in you get the error message
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| − | The NX service is not available or the NX access was disabled on host ''hostname''
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| − | When clicking onto "Detail" you get
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| − | NX> 200 Connected to address: 10.20.68.47 on port: 22
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| − | NX> 202 Authenticating user: nx
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| − | NX> 208 Using auth method: publickey
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| − | NX> 204 Authentication failed.
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| − | For every log in attempt you find the following message in /var/log/messages:
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| − | 2013-11-27T08:55:47.608389+01:00 ls3523 sshd[19975]: Connection closed by ''10.20.68.47'' [preauth]
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| − | ;Variant 1:
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| − | There is no file /usr/NX/home/nx/.ssh/authorized_keys, only a file /usr/NX/home/nx/.ssh/authorized_keys2
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| − | ;Solution 1: Copy the file authorized_keys2 to authorized_keys:
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| − | tweedleburg:/usr/NX/home/nx/.ssh # cp authorized_keys2 authorized_keys
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| − | tweedleburg:/usr/NX/home/nx/.ssh # chown nx authorized_keys
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| − | and it works
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| − | | |
| − | ;Variant 2:
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| − | If you call nxssh it does not work.
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| − | ;Solution 2: Make sure nxssh works from the client to the server. In the following example it does not:
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| − | # nxssh 10.30.67.18
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| − | nxssh: error while loading shared libraries: libcrypto.so.0.9.8: cannot open shared object file: No such file or directory
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| − | In this example install the needed [[dependencies]], for example under SUSE:
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| − | yast -i openssl-devel libjpeg62
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| − | ln -s /usr/NX/lib/libXcomp.so* /usr/lib64
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| − | ln -s /usr/NX/lib/libXcomp.so* /usr/lib
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| − | I'm taking my ermeoylps to a Tribunal and the disciplinary system is only really used by the management to settle personal scores. If everything disciplinary for like for like offences was harsh, that would be consistent and in it's own way, then fair enough.But if the offender is a management favourite they can be amazingly lenient for serious offences. They have given me some contradictory ones and are withholding others. How do I go about finding out information that they don't want me to know?Any good ideas please?
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| − | == wrong colors ==
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| − | Sometimes you see wrong colors in your NxClient like this:
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| − | [[Image:Snapshot-wrong-colors.png]]
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| − | In this case, disable compression.
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| − | == Connected to ... ==
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| − | '''Symptom:''' Your attempt to connect to NX fails after nxclient output "Connected to ''computername''". You get the error message
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| − | The NX service is not available or the NX access was disabled on host ''computername''
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| − | When you click on "Detail" you get something like
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| − | NX> 203 NXSSH running with pid: 7266
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| − | NX> 285 Enabling check on switch command
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| − | NX> 285 Enabling skip of SSH config files
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| − | NX> 285 Setting the preferred NX options
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| − | NX> 200 Connected to address: 192.168.178.3 on port: 22
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| − | NX> 202 Authenticating user: nx
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| − | NX> 208 Using auth method: publickey
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| − | NX> 204 Authentication failed.
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| − | '''Solution''', in this case for SUSE Linux 12.2 and NX 3.5:
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| − | ln -s /usr/NX/home/nx/.ssh/authorized_keys2 /usr/NX/home/nx/.ssh/authorized_keys
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| − | == authentication failed for user ==
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| − | ;Symptom: When logging in you get the error message
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| − | authentication failed for user ''youruser''
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| − | ;Solution: One time the problem was that nxserver was set to authenticate via its own password database. Instead I wanted it to use the system users. Solution was to edit /usr/NX/etc/server.cfg and set
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| − | EnableUserDB="0"
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| − | If that does not help see [[#TroubleShooting_authentication_problems]].
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| − | == Downloading the session information ==
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| − | '''Symptom 1:''' Your NX connection fails after the message "Downloading session information". When you set SessionLogLevel to 7 in /usr/NX/etc/node.cfg and try again you find in /var/log/messages something like
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| − | NX> 596 /usr/bin/xauth: /home/''user''/.nx/C-''hostname''-1007-E856077CEA415BD723D2013A45400AC9/scripts/authority:3:
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| − | bad display name "''hostname'':1007" in "add" command
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| − | '''Reason 1-1:''' NX expects to be able to connect to the localhost by using its hostname.
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| − | '''Solution 1-1:''' Make sure you can ping your local host like this:
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| − | ping $(hostname)
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| − | '''Reason 1-2:''' You do not have enough disk space left or you have a [[quota]] active.
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| − | '''Solution 1-2:''' Free up some disk space or de-activate the quota.
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| − | '''Symptom 2:''' Your NX connection fails after the message "Downloading session information". You get an error message saying: "Connection error", when you click on "Details" you get:
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| − | cat: /var/lib/nxserver/db/running/sessionId{C5763A18515642F4BE46F8488615912D}: No such file or directory
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| − | NX> 1000 NXNODE - Version 3.2.0-73 OS (GPL, using backend: 3.5.0)
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| − | NX> 280 Exiting on signal: 15
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| − | '''Solution 2:''' Create the missing folder like this:
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| − | nxserver:/var/lib/nxserver/db # mkdir running
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| − | nxserver:/var/lib/nxserver/db # chown nx running/
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| − | == Established display connection ==
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| − | '''Symptom:''' Your NX connection fails after the message "Established display connection". The log file on the server under
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| − | /home/''user''/.nx/''latest''/session contains a string
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| − | Error: Aborting session with 'Could not open default font 'fixed<nowiki>''</nowiki>.
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| − | '''Solution 1:''' It may be the X Font Server. Start it
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| − | /etc/init.d/xfs start
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| − | '''Solution 2:''' Copy over the folder /usr/share/fonts/misc from your client to the server.
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| − | == Server configuration error ==
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| − | You get
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| − | Server configuration error. Cannot log in.
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| − | Please contact your system administrator.
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| − | '''Solution 1:''' you need: a home dir for the user
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| − | '''Solution 2:''' your harddisk is full, make space
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| − | == Maximum number of allowed users ==
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| − | '''Symptom:''' When logging in you get the [[error message]]
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| − | Reached the maximum number of allowed users on
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| − | this server.
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| − | '''Solution:'''
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| − | * add your user to /usr/NX/users.db
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| − | vi /usr/NX/etc/users.db
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| − | * restart the NX service using the command
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| − | /etc/init.d/nxserver restart
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| − | == not available ==
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| − | If you get an error message that NX is not available or has been disabled, re-install it:
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| − | /usr/NX/bin/nxserver --uninstall
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| − | /usr/NX/bin/nxserver --install
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| − | == maximum session number exceeded ==
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| − | List your user sessions with
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| − | nxkill --list
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| − | Then kill them like this:
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| − | # ps -A | grep -i nx
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| − | 3435 ? 00:00:00 nxserver
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| − | 3477 ? 00:00:00 nxssh
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| − | 3481 ? 00:00:00 nxnode
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| − | 3576 ? 00:00:03 nxagent
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| − | 3579 ? 00:00:00 nxserver
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| − | 3586 ? 00:00:00 nxssh
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| − | 3594 ? 00:00:00 nxnode
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| − | 28689 ? 00:00:00 nxserver
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| − | 28732 ? 00:00:00 nxssh
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| − | 28737 ? 00:00:00 nxnode
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| − | '''''28830'' ? 00:25:54 nxagent'''
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| − | 28833 ? 00:00:00 nxserver
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| − | 28838 ? 00:02:01 nxssh
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| − | 28848 ? 00:00:00 nxnode
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| − | # nxkill --kill --pid ''28830''
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| − | === no sessions are active ===
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| − | ==== enable users ====
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| − | If you cannot log in to the NX server and get an error message like
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| − | maximum session number exceeded
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| − | AND
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| − | nxkill --list
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| − | shows you there are no active user sessions, this can be the case because your user is not enabled to log in. To find out if your user is enabled to log in, use
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| − | nxserver --userlist
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| − | You will be able to log in with all users that are shown then.
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| − | ==== Re-install NX ====
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| − | If no sessions are shown, you will have to re-install NX:
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| − | /usr/NX/bin/nxserver --uninstall
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| − | /usr/NX/bin/nxserver --install
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| − | == TroubleShooting authentication problems ==
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| − | To troubleshoot authentication problems best strace the nxclient process like this:
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| − | strace -s 99 nxclient
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| − | You will see a lot of output so you may want to redirect it to a file or filter it as described in [[piping]]. One output that you will see is what is being transmitted between nxclient and nxserver:
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| − | write(10, "hello NXCLIENT - Version 3.5.0\n", 31) = 31
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| − | write(10, "SET SHELL_MODE SHELL\nSET AUTH_MODE PASSWORD\nlogin\n", 50) = 50
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| − | You can now manually replay this:
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| − | <pre>
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| − | # su - nx
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| − | HELLO NXSERVER - Version 3.5.0-9 - LFE
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| − | NX> 105 hello NXCLIENT - Version 3.5.0
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| − | Hello NXCLIENT - Version 3.5.0
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| − | NX> 134 Accepted protocol: 3.5.0
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| − | NX> 105 SET SHELL_MODE SHELL
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| − | Set shell_mode: shell
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| − | NX> 105 SET AUTH_MODE PASSWORD
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| − | Set auth_mode: password
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| − | NX> 105 login
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| − | Login
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| − | NX> 101 User: tstaerk
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| − | tstaerk
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| − | NX> 102 Password: ********
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| − | NX> 404 ERROR: wrong password or login.
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| − | NX> 999 Bye.
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| − | </pre>
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| − | For example one time I saw a suspicious line
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| − | open("/usr/NX/etc/passwords.db", O_RDONLY) = 4
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| − | which showed me that nxserver would look in /usr/NX/etc/passwords.db for passwords. I set the respective parameter in /usr/NX/etc/server.cfg and authentication worked again.
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| − | == keypresses take long ==
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| − | ;Symptom: In the NX session you type a single key and it takes about 5 second until this key is being displayed. If you type a second key the first key is being displayed immediately. Always the last key needs a long waiting time.
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| − | ;Solution: Set "connection speed" to something higher, e.g. LAN or ADSL
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| − | = See also =
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| − | * [[FreeNX]]
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| − | * [[control A computer]]
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| − | * http://www.nomachine.com - where to get NX
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| − | * http://www.linuxquestions.org/questions/linux-software-2/nx-server-access-problem-930551/
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| − | [[Category:Concept]]
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