Unix Survival Guide: Remote Connections

Remote Connections

Connecting to the CAMLAB from the outside world

If you are familiar with Unix, you may be surprised that you cannot connect to the CAMLAB by using any of the usual commands. Incoming rsh, rlogin, rcp, telnet, and ftp are disabled because these protocols require passwords to be send unencrypted over the internet, and would make CAMLAB accounts vulnerable to so-called ``packet sniffers''.

To connect to the CAMLAB you have to use a secure version of the network utilities:

slogin replaces rlogin and telnet. This is the only way to log into your CAMLAB account from a remote computer. On the remote machine, type, e.g.,
```
  slogin cam4.math.uci.edu
```
and follow the prompt. (The CAMLAB Silicon Graphics workstations are named cam0 to cam15.) If your username is different on the remote computer, you have to type
```
  slogin cam4.math.uci.edu -l your-username
```
scp replaces rcp and ftp. This is the only way to transfer files from/to your CAMLAB account if you are working on a remote computer.
Example for copying a file named answer into a subdirectory named homework of your CAMLAB account:
```
  scp answer cam1.math.uci.edu:~/homework
```
If your username is different on the remote computer, you have to write instead:
```
  scp answer your-username@cam1.math.uci.edu:~/homework
```
Example for copying a file named letter located in the home directory of your CAMLAB account to the current directory of the computer you are working on:
```
  scp cam1.math.uci.edu:~/letter .
```
(The dot is part of the command line!) The case of different user names is handled as in the previous example.
ssh replaces rsh. Less important for users; consult the man pages.

Setting the Display

If you use slogin to connect from or to the CAMLAB, the DISPLAY environment variable will automatically be set. In other words, all X-windows that you start will automatically appear on the console you are working on - you do not have to read any further.

If you log in from the CAMLAB into a system which does not support slogin, you can set your Display variable as follows: Say you are working on cam0.math.uci.edu and you want to run an application on server.somewhere.edu. At the Unix prompt on cam0, type

  xhost +server.somewhere.edu

In a C-shell on the remote machine server.somewhere.edu, type

  setenv DISPLAY cam0.math.uci.edu:0.0

Now you can start applications on server.somewhere.edu as if you where using its console.

Logging in from Home

Most likely you don't have the ssh utilities on your computer at home. This means you have to log in via a system which provides slogin:

Faculty and graduate students should log into the Math server (math.uci.edu) as usual, and then slogin into the CAMLAB.
Undergraduates can log in via their UCInet accounts (ea.uci.edu) and connect from there.

If you log in frequently from your computer, you may want to get the ssh utilities. This is easiest if you use Linux. In that case you can even run X-window applications over the phone line. Although this is too slow for most programs, you can, for example, run Mathematica via the text based interface, and occasionally bring up windows displaying simple graphics.

ssh can be downloaded from the following sites:

ftp.replay.com for Redhat Linux RPMs. You will need two files, one of the ssh-1.2.*.rpm and one of the ssh-clients-1.2.*.rpm.
ftp.cs.hut.fi/pub/ssh for generic Unix/Linux systems.
The Ssh Homepage for documentation, and for information on ssh on other platforms

Last modified: 1998/02/21
Marcel Oliver (oliver@math.uci.edu)
The index for ``Using Unix in the CAMLAB'' can be found at http://www.math.uci.edu/~moliver/unix/index.html.