Computer Laboratory

Frequently asked questions

Does the lab have a ...

  • Scanner
    Yes, there are two in the GE11 alcove, operated by Linux+xsane and Windows+ScanSnap, respectively.
  • Public CD/DVD writer
    See Using the archive workstation on how to use an alcove workstation in GE11 for this.
  • Public ZIP drive machine
    No, but some Computing Service PWF machines have them, see Central Services News, ZIP drives on PWF PCs for details of the CS PWF ZIP drives.
  • Video Conference Facility
    See the Basic Use Guide.
  • POP3/IMAP Service
    No. People who want to use POP or IMAP facilities are recommended to use Hermes, run by the Computing Service. See for details.
  • Subversion repository service
    There are two ways to get a local Subversion repository accessible by (even external) collaborators:
    • For small, short-term collaborations, e.g. to coauthor a paper: you can grant external collaborators access to a repository in your normal filespace, by clever configuration of your ~/.ssh/authorized_keys file. Ask each of your collaborators to send you their ssh public key. Add these keys to your authorized_keys file as explained in the Subversion book section SSH configuration tricks, namely with a prefix of the form
      from="*",command="svnserve -t -r /path/to/repository --tunnel-user=username",\
      no-port-forwarding,no-agent-forwarding,no-X11-forwarding,no-pty ssh-dsa AAAABtce9euch...
      Then tell your collaborators to checkout the URL
      The command=... prefix (see "man 8 sshd") ensures that your collaborators can only talk to a Subversion server process, can only access the given repository, can only commit under the given username, and can't start a shell. The remaining prefixes disable other ssh facilities that are not wanted here either. The protection of your personal filespace relies here on the security of the svnserve command, therefore such access should only be given temporarily to a very small number of trusted individuals.
    • For large collaborations or to grant anonymous access: the department hosts several Subversion servers and repositories on dedicated servers. Additional ones can be requested from sys-admin.

Filespace issues

  • Can I have more quota?
    If the request is for a modest increase then the answer will almost certainly be yes. You should make sure you have tidied up things like unpurged deleted mail messages and Firefox cache before you ask.

    We are relatively stingy with quota not because of a shortage of disk space but because of a limitation in our backup capability. We are working on technical solutions to this, but at the moment a large increase in backed up filespace will need to be justified. It may be the case that material does not need to be in backed up filespace - we can offer bulk space on "bigdisc". Although we formally class this as scratch space, it's actually pretty resilient, being double raid protected in the filer and with the usual snapshots. You may be asked to consider this instead.

    There is also scratch space available on most machines, use sudo cl-mkscratchdir to create a filespace in /local/scratch. Local scratch space is not backed up at all, and hence any deleted files are lost. You should take care only to use this space for data that you can re-create quite trivially.

    There's a lot more material on this at Filespace in

  • I'm leaving the lab, can you keep my filespace/email address/web pages ?
    These things are kept for a while by default anyway, we don't delete filespaces on the day that you leave. Eventually file space will be archived, we can forward email indefinitely and set up WWW forwarding if given sufficient information. See Leaving the Computer Laboratory.
  • I've just accidentally removed a file. Can I get it back?
    Look in the subdirectory .snapshot (under Unix) or ~snapshot (under Windows) in the directory in question (shell completion won't find it, but it's there if you give the name in full). If you have lost a whole directory, look in its parent. There you will find snapshots at a variety of times in the past, from which you can copy files back. There are virtual copies taken of the directory on hourly, then nightly, then weekly intervals - look for copies in the lower-numbered hourly snapshots first. See snapshots

Login Account

  • Can't change password!
    If you get the error message "Token manipulation error" when you try to reset your password from a Linux machine then the most probable cause is that you are not giving a new password of sufficient complexity. Check the rules for password complexity. If you still are unable to set a password then try to do so on a Windows workstation which should give a more helpful error message.


  • Can I print a poster ?
    We have an HP DesignJet 800-42PS inkjet printer/plotter (redwood) capable of producing colour images on paper from A4 to A0 in size. Currently access is restricted due to the cost of consumables and because it requires some simple operational skills. If you wish to produce a plot then please email See Producing Posters Using Redwood.
  • Why hasn't my print job appeared ?
    There are many possibilities, the most common being that you've (inadvertently perhaps) sent it to the wrong printer. This can be easy under Windows as it is quite common to select the wrong printer from the pull down menu. Under Unix it is usually due to having your PRINTER environment variable set in the wrong place. Most people set it in the file .profile as that has always been the place Unix users have been advised to set it. Unfortunately many popular window managers nowadays (such as kde) start up before reading the .profile file. Consequently anything started by your window manager (for example as a menu item) doesn't know about the value you have assigned to PRINTER. It will consequently attempt to use the lab default printer, which is called dummy. dummy isn't a real printer, just a printer queue, and so anything sent to dummy stays in the queue until it is deleted or redirected. Use lpq dummy to see if your file ended up there. Under FC3 the correct place to set the PRINTER environment variable is in a file called .xprofile in your home directory, as this will be read before your window manager starts up. (Don't forget that you will also need an export PRINTER line for the PRINTER assignment to take effect. There is much more detail about startup files under FC3 at the Initialisation files and Configuration page.)

    If this reason doesn't apply to you see Common Printing Problems for some other possibilities.

  • Stapling on hazel & poplar
    Getting a Kyocera FS-9520DN to staple can be fiddly under Windows. See Use of a Kyocera FS-9520DN.
  • How do I print from Firefox?
    These things change between versions, but this is currently the way to do it. If you click on File and select Print you get a print popup. This shows Printer = PostScript/default, which can't be changed. However if you click on the Properties button next to it you get another popup with a Print Command: window, into which you can type lpr -Pelm or whatever. (Then click Ok on that popup, and Print on the original popup.) Make sure you also set it to A4 paper.


  • How do the buttons work on a Samsung SyncMaster 214T Monitor?
    There are 6 buttons on the front of a SyncMaster 214T monitor, in addition to the On/Off button.
    The Menu button acts as the Return/Back/Exit option.
    The next two buttons, indicated by up and down arrows, are the scroll buttons for highlighting options.
    The 4th button, is the Enter button for selecting options.

    When you press the Menu button, you find yourself in the Input screen. Pressing the down arrow takes you to the Picture, MagicColor Pro, PIP, and Setup screens respectively. Press the Enter button to select any screen of options that you require. Use the arrows buttons to navigate the options within these screens and the Enter button to access the option.

  • How do I change the contrast/brightness on a Samsung SyncMaster 214T monitor?

    To alter the screen brightness/contrast follow these instructions (use the Sync Master 214T Buttons information above to help with understanding the buttons on the monitor:

    • Push the Menu button
    • Press the down arrow once to select the Picture menu, and press Enter. The top option should be highlighted - MagicBright:
    • Press the Enter button again to access the MagicBright option
    • Here you are presented with 4 options: Entertain, Internet, Text and Custom. If you scroll through these with the arrow buttons, you will notice that the screen brightness changes. Entertain being the brightest, Text being the dimmest
    • If you are happy with one of these options, select using the arrow buttons and press Enter
    • Keep pressing the Menu button until the Monitor Menu screen clears and you can again work on your computer
    • If the first three options of brightness are not suitable, select the Custom option using the Enter button. (This will take you back to the Picture menu options)
    • Scroll down to highlight the Custom option and press the Enter button
    • Select either Contrast or Brightness, and press the Enter button
    • Use the arrow buttons to increase or decrease the amount to requirement
    • Press the Enter button to accept your changes, and either select the option to to make further alterations to brightness or contrast, or continue to press the Menu button to exit out of the Monitor Menu screen

    If may find your chosen brightness seems a bit too dark to begin with, but after a while you should find that your eyes adjust and the screen is more comfortable to work with.

  • MagicRotation - how do I turn my screen?

    The SyncMaster 214T monitors allow physical rotation of the monitor to view either as landscape (as is normal) or protrait. To alter the screen orientation, SyncMaster uses software called MagicRotation.

    By default, MagicRotation sets up a series of hotkeys which rotate your screen through different degrees of angle. Should you find you need to change your screen orientation, you can try the following key combinations:

      Ctrl+Shift+R	=	Rotate  (Rotates screen 90 degrees each time)
      Ctrl+Shift+0	=    0 degrees  (Returns screen to default position)
      Ctrl+Shift+9	=   90 degrees  (Rotates screen 90 degrees)
      Ctrl+Shift+8	=  180 degrees  (Rotates screen 180 degrees, i.e. upside down)
      Ctrl+Shift+7	=  270 degrees  (Rotates screen 270 degrees)

Operating Systems

  • Linux
  • Windows
    • Where have file associations gone in Vista?
      In Control Panel, select Default Programs
      Here you have two options:
      Set Program Associations
      In here you can select a program, such as Internet Explorer, and choose which file types you want to associate or disassociate with the program. This allows you to select numerous file types in one batch.
      Associate a file type or protocol with a program
      In here, you can select individual file types and associate them with a program. You can only do one at a time and the computer refresh tends to take a while, so if you want to associate numerous filetypes, I would use Set Program Associations.
    • How do I resize Vista desktop icons?
      Right click on the desktop and select View
      Select Classic icons to return your icons back to normal Win2k/XP size.
  • Mac OS

The network and connections

  • Can I attach my own (or a visitors) machine to the Department's network?
    Yes, possibly, but only if you are a member of staff or a research student and only subject to certain rules. Some details are at the .al network and Integrating Private machines
  • I can't connect to "some host address" ?, or, what does strict checking mean ?
    This question is usually in response to a message from ssh like this:
    No RSA host key is known for "some host address" and you have requested strict checking.
    Host key verification failed.
    and you are not offered the chance to accept the key on the basis of the fingerprint.

    Ssh is given the public key during the startup, but the purpose of the strict checking is to make sure that the host really is the expected one, and that there isn't a man-in-the-middle compromise. You need some way to convince yourself once that the public key is that of the ACTUAL machine. If you can get the system administrator at that address to mail you the fingerprint or key in such a way that you trust the information, use that.

    Otherwise, the best bet is probably to login using your user key if it is already installed (you may be able to get the system manager to do this for you) using slogin -o StrictHostKeyChecking=ask $host, and convince yourself once logged in that it really is the machine you expect. Something like ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key, should confirm the fingerprint you just received.

    In general, if you have a problem connecting to some host using ssh and need to ask us for assistance, please try using "ssh -v hostname", which causes ssh to print debugging messages about its progress. You should then cut & paste the result into your email message asking us for help.

    More on ssh at Using SSH to connect to the CL.


  • Can I have piece of software X installed on my lab-managed linux box ?
    Probably. See Software installation under Unix. (If you are using an FC3 system see bundles and yum instead.)

  • Where is java/javac ?
    Machines usually have java installed when they are set up, and have the version of the jre installed that is appropriate at the time. Thus we have a mixture of versions on different machines, and sometimes more than one version. Whatever the version it will be placed in a subdirectory of /usr/java, so that is the first place to look. The RPMs we install from do not always place links in /usr/bin, so you may have to add the /usr/java/some-version-of-the-jre/bin directory to your PATH.

    You may not have the java compiler installed by default (if you do it will also be in some subdirectory of /usr/java), in which case you may be able to install it yourself. See Can I have piece of software X installed on my lab-managed linux box ? and look for the jdk bundle.

  • I'm having difficulty finding Open Office ?
    Unfortunately the name of Open Office executables seems to be different on and within each Operating System distribution. There is a local wrapper script called soffice which tries to hide these differences and find a suitable executable, use that instead.

  • Symbolic toolbox errors with matlab
    If you get the following message while using the symbolic toolbox...
    ??? Invalid MEX-file
    /auto/groups/matlab/matlab14.3/bin/glnx86/ symbol errno, version
    GLIBC_2.0 not defined in file with link time reference.
    Try starting matlab as follows:
     LD_ASSUME_KERNEL=2.4.1 matlab &
    The problem is that some of the libraries used by matlab are rather old, and no longer fully supported under recent versions of Linux.

  • Why am I told Firefox is running, when its not?
    Every time you click on the shortcut to launch Mozilla Firefox, you get a pop-up message box saying:

    "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system."

    The and websites have solutions to this problem for Linux, Windows and Mac. Select the solution which best suits your operating system.

    The cause seems to be a .parentlock file which has remained locked after a crash, preventing further use of the application. You need to remove this file (which resides in the .mozilla folder in your home folder) to get back up and working again.


  • How do I alter fonts in Outlook 2003?
    To change font properties of email you send and receive:
    • Click on Tools, Options
    • Click on the Mail Format tab and then select the Fonts button
    • Edit the font face, size and colour as required and click on all the OK buttons to save your changes
    To change font properties of the Outlook program display:
    • Click on View, Arrange by..., Current View, Customize Current View
    • Select the Other Settings...(fonts and other table view settings) button
    • Change the font face, size and colour as desired.
      You have options to change the column views, the rows within the columns and the autopreview pane.
    • Click on all the OK buttons to save your changes

  • How do I import/remove holiday dates in my calendar?
    For Outlook 2003
    To add holiday dates to your calendar:
    • Click on the Calendar tab of Outlook
    • Click on Tools, Options
    • In the Preferences tab, click on the Calendar Options... button
    • Under the Calendar Options heading, click on the Add Holidays button
    • Select the country of holidays you want to import (i.e United Kingdom) and click on OK to this and the other two Options windows still open.
    • You should find the national holidays have been added.

    If you are using a copy of Outlook which is older than 2007, you will find that the holidays stop at the end of 2007. To import the holidays between 2008 and 20012 you will need to do the following:

    (These instructions and the 2007 Outlook.hol file were taken from
    • Find your Outlook.hol file on your local machine (for Outlook version older than 2003, this will be Outlook.txt)
      It is usually located in: C:\program files\microsoft office\1033\ or similar.
    • Rename this Outlook file to Outlook.old, just in case anything goes wrong and you want to retrieve the contents of this file.
    • Create a new file called Outlook.hol (or Outlook.txt if appropriate) and open in Notepad.
    • Copy the contents of Outlook.hol into your Outlook.hol or Outlook.txt file, overwriting the current contents.
    • Use the above instructions listed under For Outlook 2003 to import your holidays into your Calendar

      Should you need to retrieve your old holiday details, delete the Outlook.hol file you have just created and rename Outlook.old back to Outlook.hol

    To remove duplicate holiday dates, visit the Slipstick Systems website for instructions.

  • How do I set up newsgroups in Outlook 2003?

    The simple answer is you don't!

    You set up newsgroups in Outlook Express by using the instructions found on the Microsoft website (remember to replace in the News (NNTP) server section of these instructions with the newsgroup URL for your newsgroup).

    Then you set up Outlook 2003 to view your newsgroup:
    • From the Tools menu, select Customize
    • Select the Commands tab
    • From the Categories list, select Go
    • From the Commands list, select News and drag and drop into your Toolbar at the top of your screen
    When you click on News in your toolbar, Outlook Express will open with your newsgroup.

    You may also find the Computing Service Usenet webpage of use too.

  • How do I create email signatures in Outlook 2003?

    The following information is taken from the Outlook 2003 Online Help.

    • Click Tools, Options, and then click the Mail Format tab.
    • In the Compose in this message format drop-down list, select Plain text.
    • Under Signatures, click Signatures..., and then click New.
    • In the Enter a name for your new signature box, enter a meaningful name for your signature.
    • Under Choose how to create your signature, select Start with a blank signature.
    • Click Next.
    • In the Signature text box, type the text you want to include in the signature.
      (You can also paste text to this box from another document).
    • Click Finish and then OK when you have completed editing the new signature

    To automatically insert a signature in all new messages (or in all messages that you reply to or forward):

    • Under Signature for new messages, select your new signature from the drop-down list, if it hasn't already been selected.
    • You can do the same for the Signature for replied and forwards
      If you leave this as none then no signature will appear when you reply to a message or forward to another recipient.

    How to Manually insert your signature into your email:

    • It is recommended that you set up your email to have automatic signatures as explained above.
    • If you need to send an email without a signature, just delete it from your email.

  • Why do I get an error message when I try to set up my out-of-office assistant?

    "Your AutoReply message could not be displayed. The client operation failed"


    If you are a sys-admin and have access to the Exchange Server, you will find of use in helping you with this problem.
    It is a server-side issue requiring a hotfix.

    If you are an individual working on a Windows client machine and are having the issue yourself, do the following to disable Cached Exchanged mode:

    • On the Tools menu, click E-mail Accounts.
    • In the E-mail Accounts dialog box, click View or change existing e-mail accounts, and then click Next.
    • Make sure that Microsoft Exchange Server is selected, and then click Change.
    • In the E-Mail Accounts dialog box, click to clear the Use Cached Exchange Mode tick box, and then click Next.
    • Click OK, and then restart Outlook 2003.
      When you open Outlook again, it should take a bit longer to open, indicating that the Cache Exchange Mode has been successfully turned off.

    If you find that this doesn't work, you could have two instances of Outlook open. To ensure all instances have been terminated:
    - Press the Ctrl+Alt+Del keys together ONCE and select Task Manager.
    - Click the Processes tab, and check through to make sure you do not have any OUTLOOK.EXE tasks appearing.
    - If you do, select the OUTLOOK.EXE and click on the End Process button to terminate the task.
    - Repeat for all instances of OUTLOOK.EXE.
    - Reopen Outlook.

Web server

  • How can I put files on the Lab web server?
    For your personal web space, see How to export personal files to the WWW, but you should remember that when you leave the lab, this must either be removed or redirected to another private web space elsewhere. For anything that should remain in the lab after you have gone, you will need a directory elsewhere in the server. Most research groups already have a suitable area and somebody looking after it, so talk to them first. If you have something which does not seem to fit in any existing structure, you should contact for advice.
  • How do I run CGI, PHP or similar scripts on the Lab web server?
    Unfortunately you cannot do this on the main lab server. The lab web server is a mission critical server and we cannot allow user-written code to run on it. Scripts may introduce security holes, or simply consume excessive resources. However, there is now a separate server that has only access to a small part of the departmental file server and where CGI and PHP scripts can be executed.
  • Can I run my own web server?
    A web server is just a program, and any machine can run one, though it may not be possible to bind to port 80. Such a server will be available inside the department but will not be accessible from the outside. If you have a genuine need to make a private web server publicly accessible, you should discuss your requirements with well in advance. Any externally open server is a potential security risk, and moreover any web server becomes part of the public face of the department. These considerations mean that we need to take some care over what is exposed to the outside world.