Introduction
There are a number of different computing facilities available at the University of York. Ask yourselves if you have found the following when conducting your research on your local machine?
Your workload is taking a long time to run on either your local machine or the Linux managed Service. (>6hrs)
It uses all your machines resources (CPU/Memory)
You need access to lots of memory
You need access to GPUs
You are either using or producing a lot of data
- You think you could cut your job into smaller chunks and process them at the same time
- You know you want to analyse larger datasets in the future.
We have a few different machines to use when have found you are in the above position. For this tutorial we will focus on the Linux machines such as research/teaching servers and Viking. Here will will give you a very brief introduction on how to access these machines.
The research and teaching servers
These servers are also known as the Linux Managed Service or LMS for short. Detailed information on the server specifications can be found here. These machines are Desktops, similar to what you may have at home or in your office but with a large number of CPUs and memory. This means that work that your local machine is struggling with may easily be run on one of these machines. Some caveats
- They are a shared machine which means a number of users may be logged on at the same time
- They get rebooted on the first Tuesday of every month
- They run Linux so you may have to learn a little bit of Linux command line to get started.
- If you are a undergraduate you will only have access to the teaching servers.
Exercise 1 - Logging into the research or teaching servers.
There are different ways to login to the LMS depending on what operating system you are running. We will break down the different options here.
Before You Login
If you have not changed your IT Services password since August 2013 then you must do so before you will be able to login. All user password changes are manage via the My IT Account web page. Click on the Password Management (IDM) link in the Manage Your Password field to change your password. You may be given the option to 'synchronise' your password, please use this if you do not want to change your password. The password change (or synchronisation) may take a few minutes before it is visible to the servers.
Accessing research and teaching servers from off-campus
To access the research servers from Off-Campus you can either use the Virtual Private Network - VPN or the SSH gateway service (registration required).
Access from a Windows desktop
Command-line access using PuTTY
PuTTY is available on all IT Services Managed Windows systems: it is pre-installed on Classroom PCs, on Office PCs you can install it from Run Advertised Programs / Software Center. It appears under "Internet Tools" on the start menu.
On unmanaged PCs you can download the installer from the PuTTY Website
When you run PuTTY for the first time, enter the following settings (teaching0 uses the same settings):
- Add the name "research0.york.ac.uk" to the 'Host Name' field
- Check the 'Connection Type' to SSH
- Type the name "research0" in 'Saved Sessions'
- Click 'Save'
- Expand the 'SSH' tab from the 'Category' list
- Choose 'X11' from 'SSH' list
- Check 'Enable X11 Forwarding'
- Choose 'Session' from 'Category' list
- Click 'Save'
Connecting to Research0
- Start PuTTY
- Select 'research0' from the 'Saved Sessions'
- Click 'Open'
- The first time you connect you will get a security alert showing the fingerprint of the server, labeled as 'ssh-rsa' or 'ssh-ed25519'. Check the fingerprint below for the label shown and click "Yes" to proceed if it matches.
ssh-rsa 2048 5c:43:e5:e6:57:e0:4d:9f:f8:b5:ca:52:2f:30:39:ef research0
ssh-rsa 2048 bb:1f:6e:58:fa:d7:23:0d:ae:b2:b2:e8:62:a0:e7:5c research1
ssh-rsa 2048 13:42:77:57:ad:33:67:12:a4:8f:d3:26:24:37:2c:e0 research2
ssh-rsa 2048 99:da:16:61:09:e0:19:1f:53:0e:2b:e9:2a:22:50:99 research3
ssh-rsa 2048 ac:7e:1e:2a:05:d8:a1:3b:cf:b5:77:48:d0:bb:8a:22 teaching0
ssh-rsa 2048 bb:de:33:ff:07:23:6b:0a:73:ad:1f:8a:57:b2:c7:77 teaching1
ssh-ed25519 5a:c9:c1:76:16:00:42:45:f9:e5:bd:63:5d:87:db:8a research0
ssh-ed25519 f4:51:59:b7:b5:74:1c:14:a7:2c:78:1c:11:1f:72:cc research1
ssh-ed25519 76:93:b3:2d:e0:73:cb:25:a5:9e:c7:bd:ce:76:8f:a2 research2
ssh-ed25519 64:b2:f0:11:93:fc:d7:ea:12:bb:90:bc:7d:06:75:cc research3
ssh-ed25519 f4:ff:10:59:1e:5f:21:10:14:59:6e:04:16:63:7d:95 teaching0
ssh-ed25519 bc:73:f8:4f:40:7a:6b:41:73:90:f6:77:2b:4f:aa:d5 teaching1
Graphical login using x2go
x2go client is available on all IT Services Managed Windows systems : it is pre-installed on Classroom PCs, users on Office PCs can install it from Run Advertised Programs / Software Center. It appears under "Internet Tools" on the start menu - and there are pre-defined menu entries for research0 and teaching0
On unmanaged PCs you can download the installer from the x2go Website You will need to configure the settings as follows (teaching0 uses the same settings):
- If the "New session" panel does not appear, select the menu item "Session | New session..."
- Enter "research0" in the 'Session name' field at the top
- Enter "research0.york.ac.uk" to the 'Server: Host Name' field
- Change the 'Session Type' to XFCE
- All other settings can stay on default.
If you wish to change any settings:
- Cancel any login dialogs
- Click the pull-down on the corner of the panel and select "Session preferences..."
Access from a Mac
Go to 'Finder | Applications | Utilities' and run the Terminal application. Then type the following:
$ ssh research0.york.ac.uk
For a graphical login, install and configure the x2go client software as described in the unmanaged Windows section above.
Teaching0 can be accessed in the same manner.
Access from a UNIX server or desktop
To login from a terminal window, type the following from your local device with your university username (abc123):
$ssh username@research0.york.ac.uk
If you require X forwarding, type:
$ ssh -X username@research0.york.ac.uk
You will be prompted for your IT Services password.
Accessing teaching0 is done in the same manner.
Navigating the LMS and basic Linux command line to get you started
Once you have successfully logged into the LMS it may look very different to what you are use too, particularly if you are use to using windows. Please do not let this put you off. The research computing team have successfully managed to help many people use these computers who have never used Linux command line before. It takes a bit of getting use to but the more you use it the easier and quicker it will become over time.
The shell has been the major interface for the Unix/Linux operating system since it was first conceived. The shell allows interaction with the operating system through a text based interface. The shell provides the user with the following features:
- An easy to use command line interface (CLI)
- Combine existing tools to create new tools
- Input/output redirection
- Wildcard characters for filename abbreviation
- Variables and options for environment customisation
- Ability to write shell functions and programs
- Command-line editing
- Command history (quick access to previous commands)
- Arithmetic
- Command abbreviations
The user starts the shell by logging into the computer with a userid and password
****************************************************************************** *** THE UNIVERSITY OF YORK IT SERVICES *** *** *** *** THIS IS A PRIVATE COMPUTER *** *** UNAUTHORISED ACCESS STRICTLY PROHIBITED *** ****************************************************************************** login: user001 password: Last login: Mon Sep 8 14:12:44 2014 from gallifrey.york.ac.uk -bash-4.1$
The last line is a command prompt and it is the means by which the computer is telling you that it is ready to accept a command from you. If you do not see the prompt, the computer is probability still executing the last command you have typed. The user types commands which take the form:
command [ options ] [ arguments ]
Options to a command are usually proceeded by a '-' or '- -', this differentiates them from the arguments. The following example shows the echo command which prints the arguments and the ls command which take options arguments. The ls command display the users file. There will be more explanation of files and the ls command later.
Exercise 2 - Running commands in the Linux shell
When you see the prompt type the following command. You can also copy and paste the command into your terminal
echo I love York
What happens? The terminal should write out "i love York". The echo command is a small program that takes an input called a string, a series of characters and repeats them to the user.
Now try typing the following command.
ls ls -l
What do you see? Something like this?
-bash-4.1$ echo Hello World Hello World -bash-4.1$ ls bin Chemistry Desktop examples Experiments intel jobs logs tmp -bash-4.1$ ls -l total 296 drwxr-xr-x 2 abs4 csrv 4096 Jun 24 09:39 bin drwxr-xr-x 3 abs4 csrv 4096 Jun 6 09:23 Chemistry drwxr-sr-x 2 abs4 elecclust 4096 Mar 11 10:53 Desktop drwxr-xr-x 3 abs4 csrv 4096 Jun 30 12:21 examples drwxr-xr-x 5 abs4 csrv 4096 May 23 11:34 Experiments drwxr-xr-x 3 abs4 csrv 4096 Aug 14 12:26 intel drwxr-sr-x 3 abs4 elecclust 4096 Aug 15 12:49 jobs drwxr-xr-x 2 abs4 csrv 266240 Aug 15 13:48 logs drwxr-xr-x 3 abs4 csrv 4096 Aug 14 14:50 tmp -bash-4.1$
The ls command lists all of the files in your current directory. A directory is equivalent to a folder. The ls -l command gives you more information about each file or folder such as who is the owner of the file, who can access it, when it was last accessed. You can use most linux commands in a number of ways by adding extra flags. Here for ls -l we added the -l flag. If you need to know more about a command you can use either of the following
ls --help or man ls