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This chapter covers modes of communication between computers, and includes information in such areas as transferring files from one machine to another, sending commands from one machine to be executed on another, allowing remote logins from other machines, and logging onto our computing network remotely and security restrictions. The following areas will be explained:
Syntax: telnet host.domainTo access a system within MMM from within the MMM local area network (LAN), only the host portion of the address is needed. For other systems within NCAR, you must specify the host and the subnet portion of the domain name, for example,
telnet stout.atdFor systems outside of NCAR, the full domain name is required.
Once a connection is made, you will be prompted for your login and password. To end the telnet session, log off the remote machine. If your telnet connection becomes hung, CTRL ] usually breaks the telnet connection.
Syntax: ftp host.domainTo ftp to an MMM system, only the host portion of the address is necessary. For all other UCAR/NCAR systems, you must enter both the host and domain. In general, before initiating ftp, it is a good idea to change to the directory on your local machine (using the cd command) to which you will transfer the files. After you are connected, enter your login and password. When logging into an anonymous ftp site the login is generally anonymous and the password is your full email address (i.e., user@ucar.edu). Unlike telnet, only a limited number of Unix commands are available during an ftp session on a remote host. For a list of available commands, enter help at the ftp prompt. Note that ftp logs into the home directory on the remote machine. Use the cd command to change to the required directory prior to executing the get command by entering
ftp> cd directoryThe most basic ftp commands are get and put. To get a source code file, the syntax is
ftp> get remote_file [local_file]where remote_file is the file you want to get. The local_file parameter is optional. If not specified, the file will be put on your local machine with the same name as remote_file.
ftp> cd directoryTo transfer a binary file, such as a graphics metacode file or a tar file, you must specify binary prior to the file transfer by entering
ftp binaryTo put a file on the remote host, use the put command by entering
ftp> put local_file [remote_file]To retrieve a file from a remote host use the get command
ftp get remote_fileTo return to ASCII mode, enter
ftp> asciiTo transfer multiple files at once, use the mput and mget commands. With these commands, you can use wild cards (asterisks) in the filename specification. ftp asks you to confirm the transfer of each file. To use these commands, enter
ftp> mget file_specificationor
ftp> mput file_specificationAn example of using wildcards is
ftp> mget *.fThis command gets all FORTRAN source code files from the current directory. Note that to avoid having ftp query for each file during an mget or mput operation, you must initiate the ftp session with the -i option by entering
ftp -i host.domainTo exit from ftp, enter
ftp> quit
The following text illustrates the use of ftp.pl. You will first need to set the environment variable
setenv FTP_PASSIVE 1
joshua>ftp.pl ftp.cis.ohio-state.edu
www.cis.ohio-state.edu FTP server (Version wu-2.4.2-academ[BETA-15](1)
Tue Apr 14 09:10:07 EDT 1998) ready.
Name: anonymous
Password:
Hello [unknown]@joshua.mmm.ucar.edu.
This is the anonymous FTP archive of the Computer and Information Science Department at the Ohio State University.
Guest login ok, access restrictions apply.
Entering binary mode, Type set to I.
Try passive mode, Entering Passive Mode (164,107,115,3,212,185)
ftp> cd /pub/gnu
Please read the file README
it was last modified on Tue Jul 9 00:00:00 1996 - 839 days ago
ftp> get README
Opening BINARY mode data connection for README (1435 bytes).
Transfer complete.
ftp> quit
The following is an example of a PERL script that connects to an anonymous FTP site outside UCAR/NCAR and gets a file.
#!/usr/local/bin/perl
#
use Net::FTP;
$ftp = Net::FTP->new("ftp.cis.ohio-state.edu");
$ftp->login("anonymous","");
$ftp->pasv ;
$ftp->cwd("/pub/gnu");
&ftp->get("README");
$ftp->quit;
#
SCD's DSG group operates a general-use ftp server at ftp.ucar.edu. Accounts on this machine may be obtained by filing a request via SCD's Extraview Work Request System. If you do not have access to Extraview, you may place a request by calling Operations at x1200.
Two types of accounts are used on this system:
A chroot-ed "guest" account. With this type of account, you login with the ftp daemon, using your account name and password assigned by DSG. When you login, the ftpd chroot-s you down to the directory assigned to you, where you put your files. Anonymous users may then come in to pickup the files you leave.
Home directories for these accounts are usually assigned in the form "/ftp/pub/$DIVISION/$USERNAME". So if your home is "/ftp/pub/mmm/bozo", then you put your files into the "bozo" directory after logging in with the ftp daemon. An anonymous user using a browser, may pick up your files via the URL "ftp://ftp.ucar.edu/pub/mmm/bozo".
Shallower paths may be assigned if you so wish; specify what is desired when you file your request.
Please note that there is no anonymous upload of files to this system. For security reasons, that service cannot be offered.
Syntax: rcp local_file user@host:remote_file OR Syntax: rcp user@host:remote_file local_fileIn the following example, the file sample.txt is copied from the user's current machine to another system within the division.
rcp sample.txt jones@walnut:/usr/tmp/jones/sample.txtUnlike ftp, you do not need to specify binary for the transfer of these files.
Syntax:rsh remote_host -l username -n " command ; command . . . "For example, to check who is logged on to the system service14, enter
rsh service14 whoYou can execute multiple commands with one rsh command. Commands must be separated by a semi-colon. To check system load and who is logged on to service14 enter
rsh service14 uptime;who
host.domain usernameNote that different systems do not require the domain portion of the address and, in fact, will not work properly if this is specified. In our environment, the Sun systems require the domain portion of the address, but the DEC systems do not. It is useful to put double entries in your .rhosts file to cover both scenarios. For example,
laurel jones laurel.mmm.ucar.edu jonesIn addition, the username given must be that on the specified host. For instance if you specify blackforest in the .rhosts file and your username on blackforest is different than in MMM, you must specify your blackforest username.
The following are lines from an .rhosts file for the MMM user, jones, who has an SCD login name of bjones.
blackforest bjones blackforest.ucar.edu bjones fir jones walnut jonesNote that blackforest is a special case and requires both entries in your .rhosts file.
Note that anyone given access to your account through an entry in your .rhosts file obtains full access and permissions to your entire account. It is strongly recommended that you do not provide other users with this type of access to your account. In addition, an .rhosts file opens the door for security breaches. You should always keep this file protected so that only you have permission to read or write it. Use the following command to set protections on this file.
chmod 600 .rhostsIf the file is left writable by others, anyone can add themselves and obtain read and write access to all your files. The danger in leaving it readable is far less, but still exists. Because passwords are not required for rcp, it is less secure than ftp. You must weigh the convenience that this utility offers with the security risks it brings and decide for yourself.
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http://www.scd.ucar.edu/cpg/ras/
For instructions on setting up your home system for RAS access check the following URLs.
http://www.scd.ucar.edu/docs/dialup/
http://www.mmm.ucar.edu/computing/doc/winguide/ch_6/ras_main.htm
If you experience modem problems, submit an assist
request and provide the following information:
If you are outside the local calling area, you can use the 1-800-303-6227 number for accessing the Remote Access Server. The division is charged for usage of the 800 number, so use it judiciously. Additionally, you can be set up with access to the AT&T Globalnet, which will provide you with a local number to dial where you are visiting. Submit an assist request.
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The Internet consists of a vast number of machines connected to a network that complies with the Internet protocol. These systems range from high-end supercomputers to personal computers, and are connected via high-speed transmission links, such as an OC3 (155mbps) to 9600bps links on the low end. Numerous gateway systems handle transmission of data between the various Internet networks. An ever increasing amount of information floods the Internet, and is available through various tools such as ftp, telnet, and Web browsers, to name a few.
With the exponential increase of systems on the Internet over the last few years, UCAR/NCAR has implemented a security perimeter to reduce the vulnerability to security breaches. The Computer Security Advisory Committee provides recommendations to the Information Technology Council for computer security. This perimeter prevents direct access to systems inside the security perimeter. Anyone requiring access to our systems from outside must have authorization to log in through a gateway machine. Although the perimeter does provide a first level of protection to internal systems, it is not foolproof. It also makes data transfer across the perimeter more cumbersome.
In order to get to the MMM systems from the outside you have to go through the gateway machine. To request a gateway account submit an assist request. Once you are authorized on the gateway system you will need to change your password.
telnet gate.ucar.edu Username: jones Password: today.tmp ucar-telnet-proxy(? for help)> password (This is a command not your password) Changing passwords Enter Username: (your username) Old Password: New Password: Repeat New Password: ucar-telnet-proxy (? for help)>
Once logged on to the gateway you can telnet to any internal system. You will need to specify the full domain.
In order to display X Window applications to your local system from a system outside the security perimeter you will need to proxy X through the gateway system. The following URL provides details.
X-Proxy through the Security Gateway
Getting Started with SSH at NCAR
In addition, there is free software available for the Windows systems that provides secure shell connectivity. They are putty which provides connectivity to other systems and pscp which provides file transfer capability. Copies of these executables are available on the Unix systems.
/usr/common/tar/putty.exe /usr/common/tar/pscp.exeBe sure to use binary mode when transferring these files to your Windows system.
There is a Wireless Network available in most conference rooms at NCAR/UCAR.
For more information regarding the wireless network, please see the helpful documentation that SCD provides:
Getting
Online with UCAR Wireless
(this page is internal and will prompt you for your gatekeeper (or timecard)
username and password.)
RAP has some documentation also. This documentation mentions to contact the RAP Helpdesk if you have questions; instead contact your MMM system administrator (documentation provided by Carol Nicolaidis).
Wireless
Network Access at UCAR
The division laptops (which are available for MMM staff to borrow) have been set up for their wireless cards. Laptops along with their wireless cards can be reserved using the web page: http://www.mmm.ucar.edu/local/stafftools/resources.html
If you would like to purchase a wireless card for you laptop, please submit a request through the assist utility and include an account key.
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The Hummingbird Exceed software allows you to access X Window applications on UNIX workstations from a Microsoft Windows based system.
To take advantage of our pricing agreement, you can purchase Hummingbird Exceed directly from Hummingbird with your personal credit card. To do so, contact Colleen Doanne at Hummingbird. Her phone number is 650-917-2836. Please reference Volume License Number 95736-000. Cost of the software does change, but currently software and maintenance is around $130-170.
UCAR or project funds may not be used to purchase software for personal home systems.These instructions, which are pertinent to Exceed 7.1, will describe how to:
You need approximately 78 MB of free disk space to perform the installation. If you are installing on a Windows NT, 2000, or XP system then you must be logged in as Administrator to install the software.
Insert the Exceed CD-ROM. If Autoplay is enabled on your CD-ROM drive, the setup program will automatically open. If Autoplay is disabled on your CD-ROM, then open My Computer, right-click on your CD-ROM drive, and select Autoplay.
The installation program will begin, click on Install Exceed.
Select Personal Installation as the Installation Type.
The installation will prompt for the language, the default is English. Make sure English is selected and click on OK to continue.
The Setup Wizard window will appear. Click on Next to continue.
The License Agreement window will appear. Read through the agreement, select I accept the terms in the License Agreement, and click on Next.
When the Customer Information window appears, enter your name in the User Name field and click on Next.
It will prompt you for the Destination Folder where Exceed will be installed. You can accept the defaults. If you wish to change the destination folder, click on Change and select the folder where you want the installation to reside.
If you have plenty of disk space (it is recommended that you have at least 78 MB), then I suggest that you install the Complete installation. If you are short on disk space, select Typical.
Click on Install to start the installation process.
When you are prompted for the Keyboard file to be used, accept the default which is us.kbf.
When prompted for the Xconfig Password, click on Skip.
The X server tune-up window will be displayed next. Click on Next to run the tune-up. During this period, images will be displayed on your screen. Please be patient, it can take between 3 and 8 minutes to complete.
When the installation program is finished, click on Finish. Then you will be prompted to reboot your system.
After you reboot your system, You will see two icons on your desktop labeled Hummingbird Connectivity V7.1 and Hummingbird Neighborhood. Follow the instructions in the next section to configure Exceed.
These instructions will step you through creating connections to the MMM UNIX systems.
Open the Xstart utility. This can be done by clicking on Start, Programs, Hummingbird Connectivity V7.1, Exceed, then Xstart.
Once Xstart is launched, you will see the following window. This is where you will enter necessary information to connect to the UNIX systems.
Below is an example screen shot of the Xstart for the DEC systems:
To connect to a MMM UNIX workstation via Exceed, you must first be on the NCAR network. There are two ways to connect to the NCAR network:
If you are using the NCAR RAS, then connect to the RAS and double click on the icons that you saved to your desktop. The following window will be displayed. Enter you password in the password field and click on OK. Depending on the network speed, it may take a while for the xterm window to appear.
If you are using a commercial ISP and VPN, follow the instructions below for extra configuration steps. For instructions on installing and configuring VPN, please see: Virtual Private Network (VPN) at NCAR.
You must connect to your ISP and launch VPN before you can connect to the UNIX systems via Exceed.
After you connect to the VPN, then your network address of your PC will change to allow you to gain access to NCAR resources. Because of this, the -display @d option will no longer work. You need to find out what your new network address is and change the -display option. It's not as hard as it sounds.
To find out what your new network address is, put your mouse over the VPN padlock icon that will appear in your taskbar when it is running. Right-click on it and select Status. The following window will appear:
What you want to notice is the last set of number of the Client IP address information. In this example, it's 129.
Click on OK to close this window.
Double-click on the xstart icon that you created in the previous section. The following window will appear:
Enter your UNIX password and edit the command by removing the @d and replacing it with vpnXXX.ucar.edu:0.0
Where XXX is the number that you noted in the previous step (in this example, it's 129).
Be sure to remember to enter your password. Now, click on OK to connect to the UNIX system. Depending on the network speed, it may take a while for the xterm window to appear.
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