Accessing the Statistical Computing Facility Remotely
1 Introduction
In order connect to the SCF from
a remote (non-SCF) computer, you must have a
program which uses the secure shell (SSH) protocol
to communicate with other computers.
An SSH program alone will not allow you to
view graphics or images remotely.
For these purposes, you need an X Windows server
(sometimes known as X11)
either running natively on your computer, or via an
X Windows emulator.
Depending on your operating system, one or both of
these programs may already be installed on your computer.
The next section will explain how to obtain the
necessary programs if they are not already available, followed by
information on transfering files from the SCF to your local computer.
If you don't have a broadband connection,
you may find that the response when using X Windows remotely
may be too slow to be useful; but
with patience, you should
be able to access the SCF remotely with few problems.
2 Software
Linux natively runs the X Windows system, and most Linux systems
have the ssh program available to securely connect to
remote systems.
2.2 Mac OS X
The ssh command is available through the Terminal application
(available in /Applications/Utilities/Terminal.app). For versions
of Mac OS X since Panther, there is
an installation package for X11 (X11User.pkg) on the Developer Disk.
2.3 Microsoft Windows
To connect to the SCF remotely, you can use a free program called
putty. You can download it from
http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
This will allow you to run programs remotely, but it will not allow
you to use the display manager, or to view graphics.
To do this, you need an X Windows emulator.
If you have a CalNet ID, you can download Exceed 2008 from
UC Berkeley Software Distribution
A free alternative to Exceed is the
Cygwin X Windows System. There are excellent instructions
for installing this software at Cygwin/X.
Basically, you first download a program called setup.exe, which
makes it possible to install a wide variety of software; you need choose
only four packages: xorg-x11-base, X-startup-scripts, inetutils and
openssh (Clicking on the View button in the setup.exe
window until it displays "Full" makes it easier to find the
packages you need). Once everything is installed you can double click on
c:\cygwin\usr\X11R6\bin\startxwin.bat to start the system.
A terminal window will
open, and you can use the ssh command as described below.
The User's Guide
covers just about every step of installation and use of the software.
2.4 Commands
2.4.1 Microsoft Windows: putty
To connect to a remote host using putty, click on the Session category
in the left-hand pane of putty's window, and enter the hostname in the appropriate box. Click
Open, and a terminal will appear, prompting for you login name and
password.
To display graphics through putty, you need to activate
X11 Forwarding. In the left hand pane of putty's window,
click on the plus sign near SSH under the Connection category.
A choice of X11 should appear; click on it, and check the box
labeled Enable X11 forwarding.
Once forwarding has been enabled (you should only need to do it once), and
Exceed has been started,
graphics programs on the remote host will display on your computer.
2.4.2 The ssh command
If you're using a system with the ssh command, type
ssh -X username@hostname
to connect to an SCF computer.
The -X (upper case X) in the ssh command sets up the X11 Tunneling
necessary for displaying graphics.
3 File Transfer
If you want to print out your programs, listings and graphics on your
local printer, the easiest route is to copy the files from the SCF
computers to your computer and then to print them in the usual way.
The best way is to use a file transfer program on your local computer,
although other means are possible.
The command line scp command, described below, is probably
the best way to transfer files from one computer to another. If you'd
prefer a graphical client, programs like konqueror will accept the
sftp:// protocol. For example, if your username is s133xy, you
would be able to access your files on the SCF computers by going to
sftp://hostname.berkeley.edu/class/u/s133/s133xy
3.2 Mac OS X
The command line scp command, described below, can be accessed
through the terminal (/Applications/Utilities/Terminal.app). Although
the finder doesn't directly support the sftp protocol, the freeware
program Fugu provides a
nice graphical frontend to the sftp command. To use Fugu, enter
your username and
an appropriate hostname in the Connect to: field; you'll be
prompted for a password when Fugu connects to the remote server.
Your remote files will appear in Fugu's right-hand pane, where
they can be dragged and dropped to a location of your choice in the (local)
left-hand pane.
3.3 Microsoft Windows
If you've installed the SSH Secure Server software, there should be a
desktop icon labeled SSH Secure File Transfer Client. Double
click on the icon, and click on Quick Connect, and a window prompting
for
hostname and username will appear. Leave the other options at their default
values. Once you're connected, your remote (SCF) files will appear in the
right hand pane; you can drag and drop them to a suitable local location.
There are also a number of free graphical sftp clients available for Windows;
one nice and easy-to-use one is WinSCP.
If you choose the Explorer view instead of the default
Norton Commander view, your SCF account will appear as a normal
explorer window, allowing you to drag and drop files; simply enter
your username and a suitable hostname to connect.
3.4 If All Else Fails
If you can't use the previously described methods, you can email
files from the SCF system to an email account of your choice.
One way is to use the command line program pine. To send files
as attachments with pine, enter the following command:
pine emailaddress -attach file1 -attach file2 ...
After hitting Return, type control-X to send the mail, and Y to
confirm it.
Note: There is a 5 Mb limit on attachments to emails sent through
the SCF. While this should pose no problems with text files saved from the
program editor, complex graphics may be too large to send through email.
Please check the size of the file you're sending (with the UNIX command
ls -l) before reporting a problem.
3.5 The scp command
The syntax for the scp command is:
scp username@hostname:file local-directory
You'll be prompted for your password; after entering it and hitting
Return, the file transfer will start.
To use wildcard patterns on the remote (SCF) machine, precede the
wildcard character with a backslash (\). For example to copy
all the pdf files from your SCF account, to the current directory on
your local computer,
use a command like:
scp username@hostname:\*.pdf .
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