If someone knows your password, they can log into your account, read or delete your private files, or break into other computers from your account so that you get the blame. Therefore it is very important to treat your password in a similar manner to your PIN number for your bank account - do not tell it to anyone, even your closest family.
It is also important to make sure that your password cannot be guessed, even with the aid of an automatic password cracking program. You should NOT use anything too close to a dictionary word (even an obscure word), anything similar to your username, or personal information such as the names of family members. The University Computing Service has more advice on choosing a password.
As discussed above, this is a very bad idea because they could do anything they wanted with your private files. It is also against the University Computing Service's rules. Rather than sharing your account with your visitors, tell me that they are coming, and I shall set them up with their own accounts.
This is particularly important for Windows machines, because I cannot install security patches while they are in use. It is also important for machines in public areas; if you leave yourself logged on, no-one else will be able to use that computer. It is less critical for Linux machines in offices, but occasionally I perform upgrades that require the computer to be unused.
When you have logged out, the computer should display a banner with the words ``Welcome to (name of computer)'' if it is running Linux, or ``Press Ctrl-Alt-Delete to log on'' if it is running Windows.
You are encouraged to turn off your monitor and, if applicable, your office printer when they are not in use. Shutting down unused Windows machines is also a good idea, but remember that it is safer to shut them down via the operating system rather than just pressing the power button.
With Linux machines, however, it is necessary to make sure that nobody else is using the computer before you shut it down. Type ``safeshutdown'' to have the computer check for you, or read my web page on energy saving for more details.
It may simply have been delayed because the printer queues are busy, or it may be stuck, in which case multiple copies of it will just clog up the print queues more. Please see my web page about printing for more information.
If you try to print on the back of used paper, the old toner will shed and clog the printer up. Most of the laser printers cannot deal with transparencies. ps_trans and the colour inkjet can, but they have to be the right kind - ask Julia or John for some.
Before visitors can use our computers, I have to create an account for them. It looks much more professional if I can have their account ready and give them an envelope with their userid and password and my introductory information. This is why I ask for a day's notice when inviting a visitor.
In order to set up a visitor account, I need the following information:
If possible, you should ask your visitor to fill in an application for computer resources (local access only) before they arrive.
We do not have the resources to allow everyone who has ever been a member of the Statslab to keep their account indefinitely. Therefore, I clear out old accounts in October every year. We can continue forwarding your email after your account has been closed, and I am happy to keep your account open for a few months while you sort out your new computer arrangements. If you feel you need to keep your account for longer than this, please let me know why.
Computer programs sometimes crash for no apparent reason. When this happens, the program may stay around in a stuck state, eating CPU time. This is bad because it slows down any jobs running on that machine and can make it unresponsive to the interactive user.
To see what is running on your computer, type ``top''. If you see any runaway processes of yours at the top of the list and eating lots of CPU, you can get rid of them by typing ``kill PID'', without the quotation marks and replacing ``PID'' by the number in the first column. You may need to repeat the kill command or use ``kill -9 PID'', which is a more emphatic kill and should work even on processes which are too mixed up to respond to ``kill PID''. You won't be able to kill other people's processes by accident. I have a page with a more detailed discussion of killing runaway processes.
Please be aware of the memory consumption of your jobs. You can discover a computer's memory and CPU speed with the commands ``cat /proc/meminfo'' and ``cat /proc/cpuinfo'', and you can see whether any other jobs are running on it with the ``top'' command.
Nice your processes (run them at low priority so that they don't interfere with interactive use of the machine). The command to use is ``/bin/nice -n 15 command &''.
Please do not run jobs on the servers (spaces and missmuffet) as they must not be overloaded and may have to be rebooted without notice if they go wrong.
It is very difficult for me to work out what may be going wrong with your computer's setup when I cannot see it or connect to it. If you are using a college computer, your college Computer Officer will be much better able to help you than I am. If you are not a computer expert and do not have easy access to one, and you are having trouble accessing the Statslab from your own private machine, you may be better off coming in to use our computers. I have also written a web page with some tips on accessing Statslab systems remotely.
Depending on what you are trying to do, you (or your technical contact) may find it useful to know that our FTP server is ftp.statslab.cam.ac.uk, our IMAP server is mail.statslab.cam.ac.uk and our SMTP server is also mail.statslab.cam.ac.uk. You must authenticate yourself with your Statslab username and password to send email via our SMTP server (to avoid being an open relay and helping spammers cover their tracks) and also use a secure connection such as TLS or SSL.
When sshing into the Statslab, you'll need to give a computer name. Any Linux PC you use will do, or try one of the following reasonably fast machines:
This is for security, as ssh encrypts everything it transmits over the network, and telnet, rlogin and rsh do not. The correct syntax is ``ssh userid@machine''. More information on what ssh is and why I recommend it can be found on my web page about ssh.
If you wire your laptop up to a random wall-port, it is likely not to work, because the port probably will not be connected to the network switches. (Confusingly, the laptop may appear to work if it finds a wireless connection.) In addition, those ports which are connected up are split between two networks (VLANs), one for desktops and one for laptops, so disconnecting a desktop to connect up your laptop will not help, and will annoy anyone using the desktop. Wall-ports which are part of the laptop network are usually marked with a sticker or an orange cable. If there is no suitable wall-port in your office, I can wire one up, but you may find it simpler to use WiFi.
There are several different ways to connect up your laptop from the CMS, but they all require you to ``authenticate'' yourself i.e. give a suitable username and password. The use of wireless eduroam is recommended where possible. I have written a more detailed discussion of how to connect.