The most up-to-date version of this document can be found online at http://support.chem.cmu.edu/faq.html
Patches and solutions for annoying software behavior, with binaries compiled for different linux distros: Redhat 7.3, SUSE 9.3, SUSE 10.1..
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How do I get help with computers? |
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What is an andrew computer? |
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How do I know what commercial software is available? |
How do I get help with computers?
For the operation of the University maintained (andrew) computers and printers, please contact the Help Desk, or call 8-HELP.
For Windows and Macintosh computer problems and questions, please contact Seth Miller (
MI 438,
Ext.: 8-8255).
For the linux/unix Chemistry Dept maintained computers and clusters, please contact Florin (Ext: 8-3158).
The andrew computers are University maintained computers having:
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a shared filesystem (AFS) which allows the user to see the same files from any andrew computer; |
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Kerberos security for the remote services (telnet, ftp, e-mail); |
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centralized distribution and customization of software packages, upgrades, licenses, etc. |
Each CMU user gets an andrew account and a 20Mb disk quota to store files and another 20Mb quota for e-mail messages. To increase your quota see here.
How do I know what commercial software is available?
A list of software licensed by CMU can be found at http://www.cmu.edu/computing/software
Most of those packages are installed on the andrew computers.
The Chem private linux computers come with a version of Redhat or SUSE Linux modified to be as compatible as possible with the Kerberos and e-mail services offered by the Computing Services for the andrew computers, and with a set of University licensed commercial packages installed.
If you have interest in a software package which is not installed, or in a service which is not already offered, please contact Florin.
How do I access a computer remotely?
Use the "ssh remote_computer" command, where remote_computer is the name of the computer you want to access. If your computer does not have the ssh software installed, please contact Florin to get a free copy for your operating system.
If there is no way to get ssh installed and working on your computer, you can use the command "telnet remote_computer". Unless remote_computer is an andrew computer AND your telnet is kerberized, your login name and password will be plainly disclosed on the network. Even with kerberized telnet, everything else that you type may be read by somebody using packet-sniffing software. Please see the security implications below.
How do I transfer files from a remote computer?
Use the "scp remote_computer:source destination" command, where remote_computer is the name of the computer containing the file, source is the name of the file you want to get, and destination
is the name given to the file on the local computer. If the file should
be moved from the local computer to a remote computer, use "scp source remote_computer:destination". If the login name on the remote computer is different, it has to be specified as in
"scp source remote_loginname@remote_computer:destination". Please see the scp manual page for more details.
If your computer does not have the scp software installed, please contact Florin to get a free copy for your operating system.
If there is no way to get scp installed and working on your computer, you can use the command "ftp remote_computer". Using ftp, your login name and password, as well as the contents of all files transferred, will be disclosed on the network. Please see the security implications below.
What are the security implications of working on remote computers?
The first security problem appears when you use unencrypted communication channels, as telnet, ftp, and the un-kerberberized IMAP and POP e-mail clients (eudora, netscape, outlook, etc). All those applications authenticate the user by sending the user name and the password in clear on the network.
Specialized programs named sniffers are used for network monitoring. These programs, which are publicly available on many ftp sites, can be easily configured by crackers to listen the first few minutes from each newly opened connection and to pick the username/password.
On most of the networks there are sniffers running on broken accounts. If your connection is passing through such a network (and probably it does), your login name and password will be stored in the sniffer's log file and may be used later to compromise your account and/or to run a sniffer under your name and to pick more passwords on your local network. The sniffers have a passive attitude, so many of them cannot be detected from the network, and an user without special training will never realize that a sniffer is running under his own account. As a result, the crackers have available huge archives of broken accounts from most of the networks. These accounts may be used at some undetermined moment to launch illegal activities or to destroy your data.
What can you do:
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do not ever use ftp and telnet -- use ssh and scp instead; find out if the connection is encrypted each time you have to use a password or any other important confidential information which goes to a remote computer (as in the case of most of the e-mail services, subscription to different financial services offered via the web, e-commerce, etc); |
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if you are using telnet or ftp, you can minimize the exposure by changing your password a few minutes after the login. Sniffers usually listen only for the first few minutes from a newly opened connection. After that, if you change the password, the new password will not be recorded, and the password already recorded by the sniffer will no longer work; |
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change your passwords at least twice a year, just in case; |
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report to Florin any suspicious activity inside your accounts. |
Another important security problem appears when you are trying to send windows from one computer to another using telnet and X-Windows. An window can be exported only if the local X-server has set permission to give up control of the display/keyboard/mouse to the remote computer. This should be achieved by the command "xhost + remote_computer" issued on the local computer (see the xhost manual page). The xhost command opens a huge security hole because it gives to any user of the remote computer rights to control the behavior and to monitor the display, the keyboard, and the mouse of the local computer. The only secure setting of xhost is "xhost -" which denies any access, except for the local user.
What can you do:
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do not include in your login scripts any variation of the "xhost +" command; make sure that "xhost -" is the default; |
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use ssh instead telnet; the whole communication will be encrypted and compressed/faster; windows can be exported without changing the xhost setting -- ssh tricks the X-server into believing that the remote display is a local one; do not change the DISPLAY environment variable from the value which was set by ssh, even if it looks as nonsense to you -- it will blow up the whole security. |
What is my password? How can I change it?
You may have several independent passwords:
The andrew password is automatically generated when you get the andrew account, and it should be changed ASAP. The andrew password provides you access to all the andrew computers, and to the andrew e-mail account.
If you have accounts on one of the private Chem linux computers, you should have an additional password for each account, to access the local computer and the local e-mail.
The password can be changed with the "passwd" command on workstations and with the "yppasswd" command on parallel clusters.
Changing the password on one andrew computer will propagate the
change on all the other andrew computers. Changing the password on one
parallel cluster computer will make the change on all the other
computers belonging to the same cluster. On workstations the passwords
are local and independent on each computer.
It is not a good idea to have the same password associated with different accounts.
It is not a good idea to use the following types of password:
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based on a (slightly modified) dictionary word, even in a foreign language; |
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based on some information connected to your person (car numbers, phone numbers, SSN, birth date, etc). |
Those passwords can be guessed easily. One weak password endangers the work of all the users of that system, so please show respect.
How can I pick and remember an unbreakable password?
Create a password from the first letters of the words in a sentence you can easily remember.
E.g. the sentence: "Oh, how nice are Jane's shoes!" will generate the password "OhnaJs", and if you add to it a digit (or a special character), you'll end up with something like "OhnaJ3s" which cannot be broken except by (slow) brute force algorithms.
Be creative.
What's a list of andrew computers?
unix1.andrew.cmu.edu
unix2.andrew.cmu.edu
unix3.andrew.cmu.edu
etc.
Most of these computers are in public clusters or public places. So they can be down or rebooted or misconfigured at any time. If one does not work for you, try another one.
Why ssh/scp to andrew computers do not seem to work well?
SSH/SCP applications are based on keys of individual computers to realize the encryption. Doing ssh or scp to andrew.cmu.edu or unix.andrew.cmu.edu (that are not individual computers, but generic name for a pool of computers) will use one computer in the pool (say unix3.andrew.cmu.edu) for the connection. Next time ssh is used to the same andrew.cmu.edu, the connection is done to another computer in the pool having another key. So ssh/scp complains about a possible problem and sometimes aborts the connection.
SOLUTION: use ssh/scp to individual andrew computers from the list above; delete your ~/.ssh/known-hosts files if annoying messages pop-up, then try again.
How can I access the Usenet and the CMU BBoards?
The Usenet groups and the local CMU Bboards are offered via IMAP as e-mail folders for the andrew e-mail readers.
Also, there is a public access NNTP server on the CMU campus network: news.club.cc.cmu.edu
Feel free to use it with any news reader.
How can I post on Usenet newsgroups and on the CMU BBoards?
You have to use an e-mail gateway; this is achieved sending your posting as a regular e-mail to "post+bboard_name@andrew.cmu.edu", where bboard_name is the name of the Bboard which should host the posting.
How do I create a good looking pdf file starting from a dvi file in Linux?
A dvi file can be transformed into a postscript file optimized to be converted to pdf using the "
How do I know that a pdf file will look good on any platform?
Rendering pdf files depends on the fonts used by the file and if those fonts exist on the reader's computer. The solution to this is using "Type I" fonts which are actually included in the file itself, are scaling well, and will be rendered correctly and nicely by almost any pdf reader.
To
see what type of fonts are used in a certain pdf document, open the
document in the Acrobat Reader ("acroread" command in Linux), and open
the following menu:
"file" -> "Document Info" -> "Fonts"
The Linux procedure above will generate pdf files containing only "Type I" fonts.
How can I speed up Matlab 6.x?
Because of the graphical interface, many users find Matlab 6 more inconvenient to use and much slower than previous versions. Here are some tricks to get back to the old nice Matlab feeling:
Using the "matlab -nodesktop" command, no extra "desktop" will be created by matlab and the input will be done through the xterm as in Matlab 5. This will speed things out a little bit.
If more speed is needed, "matlab -nojvm" should be used. With this flag, matlab will not start the Java Virtual Machine which takes a lot of computing power and is not used by most of the users anyways.
How can I visualize data in Linux?
Good packages for graphs, interactive graphs, animation:
How can I create movies in Linux?
A
good way to transform a set of jpeg files into a mpeg-v1 movie is using
the "mpeg_encode" command. Please read the manual page "man
mpeg_encode" first and look for example configuration files in
/usr/share/doc/mpeg_encode-1.5b/mpeg_encode/examples
How can I view movies/listen to music?
If the computer has sound card, the line out connector behind the computer can be used with speakers or user-provided headphones.
Some multimedia applications:
xmovie - mpeg-1,2, mp3, some quicktimes, DVD, wav, AIFF, AC3
xine - DVDs, mpeg-1, mp3, avi, vcd
gtv - MPEG-1, mp3
ogle - DVD
How can I create mp3's in Linux?
A very good application to transform wav files in mp3 is "notlame". If you are handling wav and mp3 files on the cluster computers or workstations, please keep them inside a folder named "tmp" that can be created in your home directory, such that the large sound files will not clog the backup server.
How can I edit sound in Linux?
A nice sound/waveform editor/filter for wav files is "audacity".
How can I burn CDs/DVDs from Linux?
There are two types of CDs/DVDs that can be used:
There are several flavors of DVDRWs. For maximum compatibility and
reliability reasons, we recommend DVD-RW with a speed rating not larger
than 2x.
The filesystem on CDs/DVDs is ISO9660 which is a fixed type of filesystem: once created no files can be added/deleted. To add or delete files on a CDRW/DVDRW the disk should be first completely deleted and the new filesystem containing the old files plus the changes should be re-created. By deleting the CDRW/DVDRW the old files will be gone if they are not saved in advance.
The process of burning a CD/DVD implies several steps:Some operating systems make the steps transparent to the user. This makes the process "easy to use" but error-prone and with no flexibility. Because of that in most of the cases third party software that reveals all the stages is preferred to the over-simplified interface offered by Windows or MacOS.
The Linux application recommended for writing CDs/DVDs is "xcdroast". This application offers a simple direct way to copy CDs/DVDs, and a flexible way to master your own data CDs/DVDs using files on the harddrive. The mastering process consists into the three steps outlined above.What command should I use to do "that task"? How should I use this command?
On Unix/Linux computers use the command "apropos keyword" to find a list of commands which may do things described by keyword; then use "man command" to find out what does the command do. If you are familiar with emacs, "info command" may offer a nicer interface that can be browsed.
On Windows and Macintosh computers please use the "Help" menus.
How can I find more about computers?
A general purpose course is offered each Spring Semester.
What matlab/maple/mathematica clones developed by the scientific community are available?
scilab (developed at INRIA) or octave. Both very nice programs as easy to use as their commercial counterparts. There are even filters that convert simple scripts from one language to another.
What spreadsheets are available in Linux?
gnumeric, kspread, OpenOffice (command "soffice"). Recommended: gnumeric
The OpenOffice spreadsheet will read some of the Excel files. Otherwise, Excel files should be saved as text files and will work with all of the above applications.
What word processors are available in Linux?
Of course the power word processor is Latex.
For fans of WYSIWYG applications:
A nice and fast word processor is "abiword". It doesn't have as much features as Microsoft Word, but in the end who is using at least half of those. It can read and create MSWord documents.
Another more feature-rich word processor is the one which comes with the OpenOffice suite (command "soffice"). It can also read and create MSWord documents.
How do I configure OpenOffice the first time I run it?
Choose "Workstation Installation" (default), then pick a directory e.g. "~/.OpenOffice" for the files, browse "/usr/java/j2re.1.4.whatever" for the java interpreter.
How can I create slides or PowerPoint-type presentations in Linux?
One solution (the professional one) is to use the "slides" class in Latex. Or, for nicer graphics, you can use the prosper extensions to Latex (documentation in /usr/share/texmf/tex/latex/misc/prosper).
Other solution: A PowerPoint alike slide creator came with the OpenOffice suite (command "soffice").
How can I see/edit/print Microsoft Word/Excel/Powerpoint in Linux?
Some of those documents (especially those created by Office 97) can be handled by the corresponding applications from OpenOffice (command "soffice"). Some Word documents can be handled by the "abiword" word processor. Otherwise you should use the Windows computers.
