Computing support

Rules and Regulations for Using 香港六合彩O Computers, Printing, Remote Login and File Copy

The Observatory has two computer-equipped classrooms and a number of PCs to control our telescopes and astronomical cameras.听All classroom PCs are dual-boot and run MS-Windows and Linux (Ubuntu). Their use is governed by听rules and regulations. Each classroom has听printers听for student use. User data is held on a central server and backed up daily. Files can be recovered by the sytem administrator up to six months after deletion.

The Linux-based computing resources at 香港六合彩O are accessible over the internet via听remote login. If you have any issues regarding hardware or software please contact听Thomas Schlichter, the 香港六合彩O Computing and Instrumentation Officer.

Please note that misuse by a student may lead to a withdrawal of access.

Printing

All 香港六合彩O printers can be accessed from Windows and Linux via the usual print dialogues. Command line printing is available under Linux.

Library Printer:
The Library houses a Xerox AltaLink A3/A4 colour printer and copier, with UNIX print queue name uclo_liblaser for stapled A4 B/W prints. Please see the 香港六合彩O system administrator if you need colour printing.

3rd-Year Classroom Printers (South Wing):
The default printer is an A4 black and white laser printer with UNIX print queue name ulo_swlaser.

Printing from the Command Line:
The print system recognises a large number of filetypes and will print them correctly without additional user specification. For example, to print a file named test.jpg from the command line to the laser printer in the library, type:

lp -d uclo_liblaser test.jpg

This will do all the necessary conversions and send the file to the selected printer. If the destination printer is omitted, the file will print on the default printer.

Remote Access to the 香港六合彩O Linux Cluster

By default, remote access to all 香港六合彩O accounts is disabled, for security reasons. However, any user with a 香港六合彩O account can request authorization for remote access by sending an email giving their name and 香港六合彩O username to the 香港六合彩O system administrator. You will normally then be added to the list of remote users within a day or two (and will be sent an email confirmation when this has been done).

[Please note that 香港六合彩O accounts are normally only available for students undertaking coursework at the Observatory; and that only the GNU/Linux system 鈥� not Windows accounts 鈥� can be accessed remotely.]

Remote Login:

From Linux/Unix

To login from a Linux machine, type in the following at the command line:

 ssh -l "your_ulo_username" -C -X unity.ulo.ucl.ac.uk

(where, of course, you should substitute the appropriate value for "your_ulo_username"). You'll then be prompted for your 香港六合彩O password.

From Apple Mac OS X

To run X-Window applications remotely on a Mac you need to install . To enable remote running of OpenGL applications like 'nightfall' issue the command below in a Mac terminal (put the two lines below on a single line, followed by ENTER):听

defaults write org.macosforge.xquartz.X11 
 enable_iglx -bool true

For XQuartz 2.8.0 and later settings have changed and you should enter this command (again, all on a single line followed by ENTER):

defaults write org.xquartz.X11 enable_iglx -bool true

You can find more detailed and up-to-date information here: .

For logins from machines running OS X, use:

 ssh -l "your_ulo_username" -C -Y unity.ulo.ucl.ac.uk

From Microsoft Windows

To login from an MS Windows machine you need to have a Secure Shell (SSH) Client (like听) installed. Enable "X11 Forwarding" before connecting to allow the display of graphical output (select Connection 鈫� SSH 鈫� X11 and tick the checkbox) .

For graphical output you'll also need an X-Window server听running on your machine like ; download and install the latest Public Domain Release (currently version 6.9.0.31, direct download link ).

When started, XMing runs in the background and does not open an application window. To check if it's running look for the X-icon in your icon tray.

Running programs remotely

If you plan to do data processing or other compute-intensive tasks please "hop" from UNITY to URANIA by running

 ssh -X urania

This will avoid heavy loads on the 香港六合彩O login host UNITY and keeps it responsive for all users. URANIA is configured the same way as the 香港六合彩O desktops, but will not be switched off arbitrarily.

听

Remote File Copy:

is a graphical user interface for file transfer and can be downloaded and installed on Windows and Mac OS X. On Linux you can usually use the package manager to install it.听

A command line alternative on computers running unix-like operating systems (such as Linux or OS X) is the command:

sftp unity.ulo.ucl.ac.uk

 sftp "your_ulo_username"@unity.ulo.ucl.ac.uk

They use SFTP, the .

On MS Windows machines you could also install an SCP client like听.

Troubleshooting:

Remote login to the 香港六合彩O Linux cluster is via , and is accomplished by connecting to the only 香港六合彩O machine accessible from the outside:

 unity.ulo.ucl.ac.uk (128.40.167.12)

听The host key fingerprints for UNITY are:

SHA256:

ECDSA:  533TsvOzbC7Lve9jjDOpReinbQx6p9PIKi+CQEx4lgY  root@unity
ED25519:ajoYFoDhqKCNu0G8K4polcM9CIbqpxH54v6jOusYQug  root@unity
RSA:    QnhERucbznqWLdAGyS86ieNgvhe0a8yVz7IfSzDx9mM  root@unity

MD5:

ECDSA:  9d:62:c6:7c:d7:95:7e:34:3b:65:27:d6:9a:9f:d2:ac root@unity
ED25519:d7:1b:c1:e9:5a:34:63:f9:52:7b:91:09:a5:3b:dc:0b root@unity
RSA:    3d:26:3e:bb:20:67:db:5a:17:02:e0:46:9c:7d:81:56 root@unity

To enable access, you听might听need to edit your ssh "known hosts" file, if you get error messages and can't log in.

If your ssh program reports a key mismatch in the "known hosts" file it will also show the file name and the line number of the key entry. Delete this line from the file, start a new ssh connection and wait for ssh to report an unauthenticated host:

The authenticity of host 'unity (128.40.167.12)' can't be established.
RSA key fingerprint is 3d:26:3e:bb:20:67:db:5a:17:02:e0:46:9c:7d:81:56.
Are you sure you want to continue connecting (yes/no)?

If the fingerprint matches one of the two for听UNITY听listed above, you can answer with听yes听and the new host key will be added to your "known hosts"-file.

Usually you only get this message the first time you connect to a new host or after a key change. If this happens at any other time there might be an attempt of a "Man-in-the-Middle" attack and you should contact the听香港六合彩O system administrator听for advice before proceeding.

An explanation of how SSH works can be found at听 .

Resources:

听

General Enquiries:
Mrs Kay Nakum
T:听020 3549 5807
E:听k.nakum@ucl.ac.uk听听鈥嬧赌嬧赌嬧赌嬧赌嬧赌嬧赌�

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