Linux Logins and File Transfers
Logins are required for terminal sessions or file transfers.
Accounts and Login Hosts
Logins require a Sociology Linux account. The three hosts listed below are available for login from anywhere. A login to any of these hosts always takes you to your Linux home directory.
login.soc.duke.edu - a general purpose login system for email, file transfers, editing, web page development and password management
charisma.soc.duke.edu - the primary compute server for statistics and data management
paradigm.soc.duke.edu - the secondary compute server for statistics and data management
Logins require use of SSH (Secure Shell) connections from your client PC to the Linux server host. SSH connections are encrypted and quite secure. SSH is a native facility on Mac and Linux desktops. Windows users must install an SSH client, although this is changing as Windows is now adding a version of OpenSSH to its distribution. [Details on this to be added at a later date.]
OIT used to provide commercial SSH options, but now only recommends the open source PuTTY SSH Client software for this purpose. It installs an SSH client that provides a terminal function.
Terminal logins provide a command line prompt. User commands are parsed and executed by an underlying shell program running on the Linux host. The shell is a rich command environment that can be customized and extended through user-written scripts. Typical use of the prompt is to launch an application.
SSH File transfers
File transfer sessions are based on the Secure File Transfer Protocal (SFTP), which is part of the SSH protocol. SFTP sets up an encrypted network connection between your PC and a Linux host. This is typically represented by a graphical, split-screen interface, with browseable local [PC] and remote [Linux] directory structures. Drag and drop file transfers are performed between your desktop and the Linux host.
WinSCP is a widely used open source implementation of SFTP for Windows for which OIT provides user support.
Cyberduck is an open source SFTP implementation for Mac and Windows recommended by OIT.
FileZilla is another popular open source SFTP implementation for Mac and Windows.
Linux Graphics Display Facility
SSH when used under Windows and OS X cannot display graphical output (such as an interactive SAS or Stata session) from a Linux host. This requires a separate facility called a PC X server, to which SSH can hand off graphical output. X servers not currently native to Windows or OS X.
For Windows use, OIT licenses a commercial product called X-Win32.
There are several important X-Win32 considerations:
License Type: When installing X-Win32 on a remote desktop or a laptop, specify a node-locked license. A node-locked license allows you to use X-Win32 from any location without having to pre-load a VPN client. The node-locked license key is distributed with the X-Win32 installation materials from OIT, which includes a document explaining how to apply the key using the Activation Key method.
Annual License Renewal: X-Win32 licenses expire annually on December 31. Update your license in December from the OIT download site and install the latest version (if it differs from your current installation) to get the best performance and reliability.
SSH Tunnelling: After installing X-Win32, you must make sure your SSH terminal client is configured to tunnel X11 connections.
For OS X a free X server package available from the XQuartz download site. Install the recommended XQuartz package from the "Quick Download" link to provide X11 functionality.
Open an OS X terminal window and start an SSH session including the -X option, which ensures proper hand-off to X11 of graphical requests. This is equivalent to the "tunneling" setting used with Windows PuTTY.
When logging in from a Windows PC:
- Preload X-Win32.
- Load your SSH application.
- Select the connect option.
- Specify the desired host.
- Enter your userid and password to complete the login.
When logging in from a Mac or Linux PC:
- Open a terminal window.
In the unlikely event that your OS X login ID is the same as your Sociology userid, specify at the terminal prompt: ssh -X <hostname>
where <hostname> is from the list above
More typically your OS X login ID differs from your Sociology userid, so specify at the terminal prompt: ssh -X <userid>@<hostname>
where <userid> is your Linux userid and <hostname> is from the list above
The -X permits forwarding of graphics to the X-server on your local machine. Omit this parameter when graphics are unneeded.