Logging in without a password
To enable TotalView to connect to your parallel programs, you must be
able to log in to HPCx using ssh without supplying a password. Having
logged in to HPCx, you must also allow subsequent processes (such as
TotalView) to use ssh in the same way; this is termed "Agent
Forwarding". This involves configuring ssh appropriately on both HPCx
and your local machine.
Agent forwarding on HPCx
All users should edit the file
login.hpcx.ac.uk so that it includes the line:
Agent forwarding on your workstation
This is done differently depending on whether you are logging in to HPCx
from a Unix or Windows
Note on logging in from a Windows machine
To display graphical applications you must already be running an
X-server such as eXceed. The way in which you should configure agent
forwarding depends on how exactly how you log in to HPCx. If you prefer
to run "ssh" from an existing Unix window then you need to follow the
instructions for Unix. However, if you log in using
a Windows implementation of ssh (such as PuTTY) then you must follow the
instructions for Windows machine.
Agent forwarding on a Unix machine
You should do the following:
You must now automate the use of the key so that the passphrase is
entered once rather than for every individual login. On your local
user@workstation$ eval `ssh-agent`
Agent pid 12345
Enter passphrase for /home/user/.ssh/id_dsa:
Identity added: /home/user/.ssh/id_dsa (/home/user/.ssh/id_dsa)
(note that the quotes around `ssh-agent` are back-quotes, usually
top-left key on a standard keyboard, not normal quotes).
This caches your passphrase so that you will not need to re-enter it for
subsequent logins from this session. If you now issue
user@workstation$ ssh login.hpcx.ac.uk
then you should be logged in without having to supply any additional
passphrases or passwords. Once you can do this, you should be able to
run TotalView on HPCx.
Agent forwarding on a Windows machine
A simple way to do this is to use Puttygen, part of the PuTTY suite
available from http://www.chiark.greenend.org.uk/~sgtatham/putty/.
If you use the automatic PuTTY installer then it may fail if you select
the "Associate .PPK files (PuTTY Private Key) with Pageant" box. If this
causes a problem then you should uncheck this option and do the
association by hand later on (by right-clicking on a ".PPK" file and
choosing "open with").
You should run Puttygen and then:
The login process may then be automated with an agent. The PuTTY agent
for this is called Pageant. Once you have associated ".PPK" files with
Pageant, you simply need to double-click on your private key file and
enter the appropriate passphrase. After you have done this you should be
able to log in to HPCx using PuTTY without having to specify a password.
- Select one of the SSH2 type keys: SSH2RSA or SSH2DSA. This is a
personal choice but DSA is considered more secure. Click the "generate"
button and move the mouse as requested.
- Add a good passphrase (more than one word can be used) to the key
and optionally change the comment. Save the public key (pubkey.txt) and
private key (something.ppk).
- Before exiting Puttygen, cut and paste the public key text from the window
into the file
~/.ssh/authorized_keys2 on login.hpcx.ac.uk.
- Start Putty and edit the configuration for your login.hpcx.ac.uk
session so that you select Allow
agent forwarding in Category Connection => SSH => Auth
Running graphical applications via ssh
It is possible to configure ssh to automatically forward the output of
graphical applications to your workstation. For this to work, you must
NOT set the DISPLAY variable by hand; it will be set automatically for
you. Normally this should simply happen, but if you are having problems
you can try the following:
Certain ssh implementations feature trusted X11 forwarding
(-Y option for ssh) which can also be used to resolve potential
- add the following line to your
- If you are using PuTTY from a PC, edit the configuration for your
login.hpcx.ac.uk session so that in addition to agent forwarding
you select Enable X11 forwarding
in Category Connection => SSH => Tunnels
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