skip to primary navigationskip to content
 

Using an MCS Linux PC

An introductory guide to using Linux on a Managed Cluster Service desktop.

mini

Introduction

This page is about using Linux on a PC in a Managed Cluster desktop. MCS Linux can also be used by remote login from any system. See also information on using DS-Files in MCS Linux and on printing using DS-Print.

In the instructions below, click means click the index finger button (left-hand button in the default mouse setup) unless otherwise specified.

Logging in

You will usually find that a PC in a MCS room is already switched on, and displaying a Windows information/start screen. If the screen is blank, move the mouse to wake the display. If the machine is switched off, switch it on and go to step 2, below.

  1. Hold down the Ctrl and Alt keys while pressing Delete.  This will present the Windows login screen.  In the bottom-right of the screen, press the power symbol.  From the menu that appears, select Restart.  The computer will reboot.

  2. After some preliminary start-up checks, the system will ask you to select which operating system to start; use the down arrow key to highlight MCS Linux and then press Enter ↵ to confirm your choice. If you wait too long to make your selection, the system will start the default operating system, which for most machines is Windows.

  3. A blue splash screen will appear and the system will boot into MCS Linux. If the system has to update itself this may take some time, and it may automatically reboot if so.

  4. Once the machine has finished loading, it will display the system login screen (shown below). It will show a dialog box asking for your username. Enter your CRSid (e.g. spqr99) then press Enter ↵.

  5. The dialog box will then change, asking for your password. Enter your UIS Password, then press Enter ↵.

  6. Your desktop will then load.

MCS Linux login screen
MCS Linux 2018–2019 login screen

Please remember to log out when you have finished. Failure to do so could result in another user reading, altering or deleting your files, or sending emails from your account.

The desktop

MCS Linux is based on Ubuntu and uses the Unity interface to the GNOME desktop environment. Once you have logged in, the login window shows the Message of the Day, icons representing your desktop files, and the top menu bar.

log in screen

The top menu bar contains, from left-to-right:

  • the 'Activities' button, for starting applications, or managing existing windows;
  • the application-specific menu, which changes depending on which application has focus;
  • the central clock, which can be clicked on to see a calendar, and see notification messages;
  • the accessibility menu, which can be used to toggle different accessibility features, such as extra-large text;
  • the keyboard layout selector, which lets you change the keyboard layout from the default English (UK) layout;
  • the power menu, which allows you to switch off or log out from the machine, or change your desktop settings.

Accessing applications through the menu system

Applications can be started by moving your mouse cursor to the far top-left corner of the screen, or left-clicking on the Activities menu.  This will bring forwards the launcher for commonly used applications; in order: Files, the Firefox and Google Chrome web browsers, the Thunderbird mail client, the LibreOffice suite, the GEdit plain-text file editor, and Terminal. To start one of these, single-click on the icon using the left mouse button.

To access the other applications in MCS Linux, click the last icon at the bottom of the launcher, Show Applications:

log in screen

The main window that appears will then show a grid of icons across the screen, each of which representing some program or tool available on the system. At the bottom are two selectors, Frequent or All, to change between showing all of the programs available, or just those you have used frequently.

You can also start tying the name of the program or function you're looking for, and the set of icons will be reduced to only those that match the words you type. If not all the icons will fit on the screen, they will be spread over several pages.  You can click on the hollow dots that will appear on the right side of the screen, or use the wheel on your mouse (if available) to scroll between successive pages.

Mouse and window operations

The main operations you may want are:

  • Mouse buttons: Clicking the right mouse button, for example on a window or on the background, gives a context-sensitive menu.

  • Windows: In the top corner of each window are three buttons that can be selected with the left mouse button (Window ops). The left button minimises the window the window, hiding it from view; the centre icon will maximise the window (to fill the screen), and the right button closes the window. You can also:

    • Click and drag on the border of a window to resize it.

    • Click and drag on a window's title bar to move the window around the screen.

The command line interface

The fundamental application on an MCS Linux system is the command line interface, or shell, because every application that can be launched from the menu system can also be launched from the command line and there are many applications and utilities that only work at the command line. The shell also provides a syntax for combining commands and for running commands only under certain circumstances. If you want to do any automation for processing large numbers of files then you will need to understand the command line. If you are happy with the applications and commands provided by the menu system then you need not worry about it.

You can launch a window running a shell by clicking on the Terminal icon in the launcher, available under the Activities menu.

Terminal window

Once you see the prompt (dwm37@angleton:~$ in the image above) you can start typing commands.

Changing your password

See the instructions in IS 6: Changing/Choosing Passwords. If you have forgotten your password you will need to have it reset. See the FAQ on What should I do if I've forgotten my password or it doesn't work?.

MCS news

The Message of the Day is sourced from the UIS News service, and displayed at login-time.

Customizing the graphical interface

You can change the behaviour of much of the standard interface by using the Settings application, accessible by pressing the power symbol in the top-right corner of the screen, and selecting the screwdriver-and-spanner icon (MCS Linux Settings (2018–2019)) in the bottom-left of the menu that appears.

Additionally, we have also installed the GNOME Tweaks tool.  This can be found in the Activites → Applications menu, and provides additional ways to customise the presentation and behaviour of the default desktop, including changing fonts scaling options, customisation of different typefaces, or turning on and off any extensions to the desktop shell that have been installed by you or the system administrator.

Accessibility aids

The MCS systems are designed to be used by the widest possible audience and the operating systems include features that allow those with special needs to adjust their interface.

Standard facilities

The built-in accessibility facilities can be accessed from the Accessibility menu on the top menu-bar (MCS Linux Accessbility (2018–2019)), and allows quick control over the following settings:

  • High-contrast rendering of screen elements;
  • An on-screen zoom magnifying glass, that magnifies the entire screen around the mouse cursor;
  • A Large Text function, that tries to cause all text to be rendered bigger;
  • Screen Reader support, that causes desktop actions to be described as they occur;
  • An on-screen keyboard, that allows keyboard button presses to be emulated using a mouse;
  • A Visual alert option, that causes the normal system bell to be replaced with a screen flash;
  • Sticky-, slow-, and bounce-key options;
  • Mouse Key support, which allows for keyboard control of the mouse cursor.

Further support

We publish general information and advice regarding accessibility issues of many kinds.

Applications available on MCS Linux

See the full software list for MCS Linux. Particular applications worth noting are:

Email

The supported mail clients are ThunderbirdEvolution, and the command-line Alpine.

  • To use Alpine type alpine at the command line or, from Activities → Show Applications → Alpine. Alpine is preconfigured to connect to Hermes.

  • To use Thunderbird, type thunderbird at the command line or, or from the launcher under Activities (MCS Linux Thunderbird (2018–2019)). Thunderbird will not be preconfigured, but has been pre-programmed with the details of the Hermes mail service; it should automatically fill in the right settings if you tell it your username is crsid@cam.ac.uk.  If you require further assistance, have a look at the Thunderbird for Hermes help pages.

  • To use Evolution (email, contact management, appointment and task scheduling), type evolution at the command line or, from Activities → Show Applications → Evolution. Evolution is not preconfigured so if you wish to use it you will need to configure it; see Mail program settings for Hermes for help.

The Hermes webmail service is available using any browser.  Management of your Hermes email account (e.g. vacation messages, spam filtering) should be done through this webmail interface.

Exchange Online

Please note that the only supported interface for accessing Exchange Online from an MCS workstation is by web-browser.  In particular, we specifically advise against attempting to use the IMAP interface to Exchange Online.

Web browsers

Firefox is the supported browser and can be started by single-clicking the icon in the panel (firefox icon).

Google Chrome is also provided — in three different versions.  Most users interested in using Chrome will want to use the stable version, which is included in the panel by default (MCS Linux Chrome (2018–2019)), however the beta and unstable versions of Chrome are also supplied and may be useful for users wanting to experiment with browser features that are not yet finished.

Chromium is also available and can be accessed from Activities → Show Applications → Chromium Web Browser.

The Text-based browsers lynx and w3m are also available; to start these type the program name in a terminal window.

You will need to configure any unsupported browser that you wish to use.

Logging out

To log out click on the power icon at the right of the menu bar at the top of the screen, and select the circular Log Out button (MCS Linux Logout (2018–2019)). Doing this returns you to the login screen, from which you can login to Linux again or choose to reboot the system, e.g. into Windows. A machine left in this state for roughly 45 minutes will consider itself idle.  By default, idle MCS Linux workstations will reboot themselves into the default operating system on the system; on most machines, this will be Windows.

Known issues

Home directories exhibit some unusual behaviour

The network fileserver that hosts home-directories runs Windows.  As a consequence, it does not understand some Unix-specific conventions.  Specifically:

  • The file-server does not understand executable-bits.  To work around this issue, all files in your home-directory will be treated as having the executable-bit set. It is not possible to remove the executable bit from any file in your home-directory.

  • The Windows file permissions model does not map cleanly onto the Unix user/group/other model.  As a consequence, the file permissions presented on MCS Linux systems are only approximations, and do not reflect the true underlying file permissions. You can query the true underlying file permissions by using the specialist getcifsacl command, but you will need to be familiar with the Windows ACL permissions model in detail to understand the output.

  • It is not currently possible for you to grant other users selective access to your personal files using the chmod (or an equivalent) command. It is possible to use the specialist and setcifsacl to manipulate file permissions, but this is an advanced utility intended for experts.

  • The file-server is case-insensitive. This is unusual for Linux and Unix systems, and means that it isn't possible to store two distinct files in the same directory with names that differ only in their case.  This has the consequence that you can give a filename in the wrong case when attempting to access a file, and that access will still work.

    For example, if you have saved a file called AAA.txt, and attempt to read it using the name aaa.txt, this will succeed. However, if you then try to save a new file in the same location called aaa.txt, or Aaa.txt, or aAa.txt, or similar, this will not create a new file, but will instead overwrite the original.

sudo commands will not work

The purpose of the sudo command is to run a specific program with administrative privileges.  Programs run with such privileges are not subject to the normal safety features that prevent modification, damage, or subversion of the operating system.  Therefore, the use of such commands is not allowed; any attempt to use a sudo command will result in a warning.

If you believe that an MCS Linux machine is broken, misconfigured, or lacking some essential functionality, please contact the service desk for support and advice.

Screen-locking is disabled

As a matter of policy, the ability to lock an MCS Linux desktop has been disabled, in order to avoid cases whereby a user leaves a machine locked for an extended period of time, preventing others from using it.

Changing your shell is not supported

All user accounts on MCS Linux are hard-coded to use the Bourne Again Shell, also known as bash.  It is unfortunately not possible to change your user shell.  If you try to change your shell using the chsh command, it will return the (somewhat misleading) error, "chsh: cannot lock /etc/passwd; try again later.".

Further information

UIS operates training courses that may be valuable to new Linux users, including Introduction to the Command Line Interface and Simple Shell Scripting for Scientists.