Logon from Linux

Required software

A SSH (Version 2 compatible) client is required for logging into the HPC resources from a UNIX machine. These are normally packaged with the Operating system. To find out whether these are installed into your path on your system, simply open up a terminal and type:

$ which ssh
at the command prompt. If this reports that ssh is not in your path, either install a SSH client (based upon ones found at http://www.openssh.com/) or get your system administrator to do so.

Logging in

To log into the Arc systems using secure shell simply issue the following at the command prompt:

$ ssh @facilityname.leeds.ac.uk

(where <facilityname> is arc3 , arc2, marc1 or polaris )

So, to log in to Arc2 (for example):

$ ssh @arc2.leeds.ac.uk 

You should be prompted for your password which you should enter.

All the examples below refer to Arc3. For access to other HPC facilities, simply replace arc3 with arc2, marc1 or polaris .


Secure shell allows X display (GUI) traffic to be tunnelled (and encrypted) through the SSH connection. To enable this, first check the status of your local display by typing:

$ echo $DISPLAY

on your local machine. If this returns something like hostname.leeds.ac.uk:0 , then the variable is set correctly. If it is undefined you will need to set it by e.g.:

$ export DISPLAY=hostname.leeds.ac.uk:0

for bash/sh or in csh:

$ setenv DISPLAY hostname.leeds.ac.uk:0

Provided your local display is set up correctly, the -X flag can be used to allow X11 forwarding:

$ ssh -X username@arc3.leeds.ac.uk

Please note that recent versions of the secure shell client have an “Enable X11 trusted” -Y flag which should be used instead of the -X flag:

$ ssh -Y username@arc3.leeds.ac.uk

For the recent clients, the -X flag will still work, however some applications do not work properly on the remote server if -Y is not used.

File transfer

The ssh tools come with two clients for file transfer: scp (secure file copy) and sftp (secure version of FTP).


Using scp is very similar to the normal copy ( cp ) and remote copy ( rcp ) commands in UNIX:

$ scp

In the above <target> and <destination> correspond to the files being transferred. A local file is specified by its filename, a remote file is indicated through the syntax <username>@<machine>:<path> . If a / follows the : , the path is taken from the root of the filesystem, however without a / the path is taken relative to your home directory. e.g. to upload a local file to your home directory on arc3 issue:

$ scp file @arc3.leeds.ac.uk:

Similarly, a file can be downloaded with:

$ scp @arc3.leeds.ac.uk:file .

(note that . will put the file in your current directory.)


SFTP can be used in a very similar way to other command line FTP clients. To establish a connection to Arc3 (for example):

$ sftp @arc3.leeds.ac.uk

and to Polaris,

$ sftp @polaris.leeds.ac.uk

You will be asked for your password and presented with the SFTP prompt when connected. Typing help or ? gives a list of commands. Similar to FTP, cd will change the remote directory and lcd change the local directory. put and get can then be used to upload and download files.

User and machine names

Please note that if your local username matches your username on the HPC platform, there is no need to specify the <username>& portion of the commands above. Furthermore, if you are connecting from a machine within the leeds.ac.uk domain, it is not necessary to include this; e.g.

$ ssh arc3

will log you into Arc3, provided you are connecting from a machine which is on campus and your usernames are identical on the local and remote machines.