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NX FAQ

Make sure to check out the "Tutorial"

HERE

What Version of NX Player Will Work?

You need the latest NX Player (4.0.255 or later), please refer to the Tested Player Page for downloading instructions. 

My Font Size is TOO BIG/too small?

To change the font size inside your terminal (Konsole Application): In the menu of Konsole Application, choose "Settings"->"Manage Profiles", then click "Edit Profile...", now you can change the font size in the "Appearance" tab, after changing, click "OK" until you are back to the terminal. Now Every new terminal window you open will have the new font size. 

To change the font size of your menu bars/window titles: Right click on an empty desktop then choose "Konsole", inside the Konsole, type "kcmshell4 fonts". Then you have a dialog box to change your font size. 

How to Resize My Screen

With the latest NX Player (4.0.181 or later), the most effecient way is to enable "Remote Resize" in the NX menu. To do so:
1. Connect to NERSC NX, until you see your desktop;
2. Bring up the NX Player Menu with a Hotkey: 
Mac: Ctrl+Option+0, Windows: Ctrl+Alt+0, Linux: Ctrl+Alt+0
3. Choose "Display" submenu, then toggle the 2nd button until it shows "Remote Resize Enabled" 
Now you can freely resize your NX Player window and the remote desktop will resize accordingly.  

Emacs complains about missing fonts and shows white blocks?

This is due to a problem with font server. Please use the following command instead:

emacs -font 7x14

What Keys are used in NX at NERSC?

Two pairs of keys are used in NERSC NX service. 

1. The NX system key pair (NX Access Key). This is the key pair that allows the NX client to connect to the NX server. The private key is included in the downloadable configuration file and on the webpage. Note that NX client softwares will come with a default private key, so if you did not configure your client properly, you might see "Authrization Failed" error message. 

 2. The NERSC NX key pair. This key pair is only for NERSC. This key pair allows user to connect to different NERSC machines from inside NX, without typing the NIM password each time. The private key is installed on the nx.nersc.gov host, the public key is installed to the user's global home. If you experience any problem with this key pair, you can try to re-generate the key pair by choosing "SSH Agent"->"Regenerate Keypair".  

What Passwords are used in NX at NERSC?

Two passwords are related to the NERSC NX service:

1. Your NIM password. This is the password you will use to "LOGIN to NX", i.e. use it before you see the NX desktop. You can change this password at nim.nersc.gov

2. Password for your NERS NX Key pair (No.2 in the previous FAQ What Keys are used in NX at NERSC). You need to use this password when you click on the "NERSC Systems" menu INSIDE NX. To change this password, you need to choose "Regenerate Keypair" from the "SSH Agent" menu inside NX. 

How to Manually Kill a Frozen Session?

USE WITH CAUTION, this will kill one or more running sessions and all unsaved work will be lost. Your NX session may run on either of the following 2 servers, you need to login to both to kill all your leftover processes. 

1. Login to nx node mndlnx01-69.nersc.gov

ssh NIM_username@mndlnx01-69.nersc.gov

2. Use ps to get a list of runing nxnode or nxagent agents

ps -ef|grep $USER|grep nxagent
ps -ef|grep $USER|grep nxnode

3. use kill to kill all of nxagent and nxnode processes

The 2nd field from the output of the ps commands above is the PID, to kill a process use 

kill -9 PID 

4. Repeat step 1-3 with the 2nd NX server: mndlnx02-69.nersc.gov

5. Try to connect again

"Can't start CUPS server"?

Please upgrade to the latest NX Player (4.0.181 or later). 

 

Keypair, SSH Agent and NX

The NX server acts as a gateway to all other NERSC systems.  Users access other NERSC systems via SSH.  SSH Agent is used to help simplify the authentication from the NX server to other NERSC systems so that you do not need to type a password each time a new connection is created.  You can click on the "SSH Agent" menu to manage SSH Agent behaviors. 

Generating a Keypair

SSH Agent requires a keypair to function.  The first time you click an item on the "NERSC Systems" menu the keypair is created and installed.  You need to provide a password to encrypt your private key.  This password can be different from your NIM password.  You can regenerate the keypair by selecting the "(Re)generate Key Pair" menu item from the "SSH Agent" Menu.

Loading the Keypair

SSH Agent can load a keypair into memory and use it as the authentication method to other NERSC systems.  A keypair will be automatically loaded when a user tries to connect to a NERSC system via the menu.  After the keypair is loaded it will remain active until it is removed, i.e., the user can login to any NERSC system without entering a password each time.

SSH Agent Credential Removal Policy

For security reasons the NX Server will remove the loaded keypair from the SSH Agent on any of the following occasions (meaning you will need to type the keypair password again next time you connect to a NERSC System):

      • You suspend or terminate the current session;
      • You are inactive for 30-minutes;
      • 12 hours after the keypair is authenticated (12 hrs key lifetime).

Suspending or Terminating a NX Session

When you close the NX window (e.g., by clicking the "cross" button) a dialog box will appear providing the choice of either suspending or terminating the session.

      • Suspending the session will preserve most running applications inside the session intact and allow you to reconnect to the session at a later time.
      • Terminating the session will kill all the running applications inside the session and all unsaved work will be lost.

If you lose your connection to the NX server (e.g., if your internet connection is lost) NX will automatically suspend the session allowing you to reconnect to the same session while keeping the running applications intact.

 

 

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