SSH (Secure Shell)
Why I advise you to use ssh
If you use telnet or rlogin, everything you type including your
password is transmitted in clear over the network, so a malicious
cracker could use a packet sniffer to collect passwords. This is why
the CMS firewall blocks any attempt to telnet or rlogin from the
outside world, and why the new computers don't accept telnet or rlogin
connections at all. If you use
ssh, everything that is transmitted over the network is encrypted,
which is much more secure.
Also, ssh is much more convenient if you are using X Windows. It
handles X forwarding automatically, which means that if you ssh from
machine A to machine B, your session on machine B will automatically
be able to pop up windows on machine A's display. If you were to use
telnet or rlogin, you would first have to set the DISPLAY environment
variable on machine B to the right thing. Then if machine B was not
within the Statslab, you would either have to fiddle around with the
xauth command, or use xhost, which would allow anyone on machine
B to access your display on machine A.
How to use ssh on an Unix system including Macs
The syntax of the ssh command is ``ssh username@machine.name'',
replacing ``username'' with your username on the remote machine and
``machine.name'' with the name of the remote machine. If your username
is the same on both machines, you can abbreviate the command to ``ssh
machine.name''. For example, to ssh from sirtommy to zodiac I would type
``ssh zodiac'', but because my username is ``eva'' for my Statslab
account and ``erm1001'' for my Hermes account, if I wanted to ssh to Hermes
I would type ``ssh erm1001@hermes''.
The message ``Warning: host key not found from the list of known
hosts. Are you sure you want to continue connecting?'' will appear
the first time you connect to a particular machine. Answer yes (you
must type the word ``yes'' in full here, not just ``y'') and you won't
be asked the question again when sshing to the same machine.
The message ``Secure connection to machine.name refused; reverting to
insecure method'' means that the remote machine does not have ssh
installed. This will not happen with any Statslab machine. If it happens
with a machine outside the Statslab, you could ask the administrator
of that machine to install ssh.
How to use ssh under Windows
PuTTY is the ssh client which we have installed on our Windows
machines. You can download it from
the PuTTY download page. To use PuTTY, first go to the Colours
tab and change the default foreground to black and the default
background to white (or any other combination you like - I find the default
colour combination ugly and difficult to read). Then go to the
Connection tab, select the ssh button and type in the name of the
machine you want to connect to, and click Open to connect. To save
your settings for connections to a particular machine, type a name
into the Session Name box and click Save. Then when you want to
connect to the same machine again, all you need to do is click on your
session name and then Load before clicking Open.