UNIX Lab Manual A Guide to UNIX Workstations The University of Maryland at College Park Department of Geography Turner Instructional Computer Laboratory Revised July 2000

1.1 Laboratory Resources: description of facilities

2.1 Laboratory Operations

2.2 Lab Assistants: the role of lab assistants
2.3 Class Related Questions: where to direct class related questions
2.4 Hours of Operation
2.5 Acceptable Use Policy

3.1 Open Lab Rules

3.2 Sun Workstations: about the Suns and rules pertaining to the Suns

4.1 Logging into an Account: how to log in and change your password

5.1 The UNIX Operating Environment

5.2 Navigating on the Screen: icons, X-term windows, windows (moving, resizing, minimizing, maximizing, closing)
5.3 About Your Glue Account: your home directory, your quota
5.4 The Dash Board
5.5 Commonly Used Dash Options
5.6 Copy/Paste Operations

6.1 Basic UNIX

6.2 UNIX File Structure
6.3 Basic UNIX Commands
6.4 Intermediate UNIX Commands
6.5 Special UNIX Command Operations

7.1 Where to Get Help

1.1 LABORATORY RESOURCES

The Department of Geography operates a well equipped Computer Mapping and Spatial Analysis Laboratory. It is open to UMCP students, faculty and staff who have a GLUE account through the Department of Geography. This guide is not intended to be a comprehensive UNIX manual. Rather, it is a guide to the Glue UNIX system in the Geography department.

The laboratory is connected to most campus computer facilities through the UMCP UNIX network, GLUE, enabling users to access computers, and/or send electronic mail anywhere in the world. Using the network, users can also access an on-line catalog for all libraries within the University of Maryland system, as well as the Library of Congress, browse the World Wide Web (WWW), and access information about The University of Maryland and the Department of Geography. The specialized Geographic Information Systems (GIS) and remote sensing software are utilized in Geography Department courses, providing students with hands-on experience with high- level computing.

The facility has thirty workstations. UNIX is the operating system that is employed by the SUN workstations; the GLUE network provides connection to most campus computer resources. The Geography Department open lab has six gigabytes of on-line data storage dedicated to class projects and academic needs.

Input devices include two large (40x60") digitizing tables, floppy and CD- ROM readers. Output devices include a Tektronix Phaser 140 inkjet 360 dpi color postscript printer and a Hewlett-Packard 4m 600 dpi black and white postscript printer.

Instructional and research needs are met by a varied and advanced set of software, including some locally developed, for digital cartography, spatial modeling, geographical information systems, and remote sensing. The software available in the lab are used on research projects in the department and include: ARC/INFO geographic information system, ArcView, PCI remote sensing software, and S-Plus statistical software. The department also has an extensive on-line spatial database.

2.2 Lab assistants:

• Any questions concerning laboratory policies or how machines function in the laboratory should be addressed to the assistant on duty. The assistants will help access accounts, and can answer many UNIX questions. Also, assistants will help in all printing matters. Please ask any questions on printing before printing (mistakes may cost money).
• The assistants will help users enter and exit the software packages required for classes. However, they are not necessarily experts in the software packages and cannot be expected to answer detailed questions specific to the class software nor to instruct users how to use specific software packages.
• The assistant on duty should be asked about problems with the computers, or general questions. If they do not know the answer, they will attempt to find out by sending an e-mail to the Geoghelp account.

2.3 Class Related Questions:

• For problems with software, assignments, and theories used in a class, seek out the class TA or professor for assistance.

2.4 Hours of Operation :

• The laboratory is open a minimum of 40 hours per week during the fall and spring semesters. These hours vary from semester to semester based on class schedules and the hours assistants can work. Please call (301)405-4075 or check the open lab website. During the summer, hours are set by class instructors and TAs.
• Classes regularly use room 1138 and this room is closed to the public during class hours. In most circumstances, 1136 will be available to users if a class is scheduled in 1138.
• The laboratory may be reserved for occasional demonstrations. Calendars posted on the door list such closings and every attempt is made to provide at least one week's notice.
• During open laboratory hours, anyone with a UMCP ID and a Geography Glue account is welcome to use the facilities.
• After hours, only those people with the access codes are allowed in the laboratory

2.5 Acceptable Use :

• The Computer Science Center's ACCEPTABLE USE POLICY applies to this laboratory.
• GLUE accounts can be accessed from home. This option is available to all GLUE users with the use of a modem on a home computer, though not all software or graphics windows will function. Call the CSC Consultant Laboratory at (301)405-1500 for information about connections.

Any abuse of rules, computers, furniture, or assistants will not be tolerated. Assistants may ask anyone breaking rules to leave the laboratory. Penalties such as disabling accounts and loss of privilege to use the laboratory are also possible.

1. Food and drink are NOT allowed in the lab at any time.
2. Smoking is NOT allowed at any time.
3. Word processing is NOT allowed unless it is related to a Geography computer course. Please use other computer facilities for word processing related to classes other than Geography computer courses.
4. Do NOT open the doors for anyone. If the assistant is late, do not prop open the door.
5. Copying of software is a violation of copyright laws and licensing agreements, and is NOT allowed at any time. Class text or data files (other than personal) may be copied only with consent of the instructor.
6. Please pick up your own trash. The room's cleanliness is up to you. Recycling bins for white paper are located in the lab.
7. Manuals may NOT be removed from rooms 1136 or 1138.
8. Certain materials such as manuals may only be used with an assistant's knowledge. Other materials that are locked up or otherwise inaccessible are only available from assistants. Do not try to gain access to restricted materials without an assistant.
9. Do not leave workstations for longer than 15 minutes. If gone longer, the assistant will log absent users out. Locking screens is NOT allowed.
10. All printing is on a pay per sheet system. See the printing section for more information.
11. Please do not be overly loud or otherwise bothersome to the others in the laboratory. Personal radios/cassettes may only be used with earphones, and then only on low. Study parties are not permitted. If it is necessary to work in groups, please go elsewhere.
12. Please do not ask off duty assistants for help. Direct all questions to the lab assistant on duty.
13. Remote logins are not allowed for intensive processing, especially graphics. Do not remotely login in during class time. Anyone remotely logged in on unauthorized machines or during class time, or performing high-CPU processing, may be logged off immediately.

3.2 Sun Workstations
 

• Never turn off a SUN Workstation. Turning off a SUN can cause serious damage to the computer, and should never be done. If you experience any problems with a SUN Workstation alert the lab assistant on duty.
• There are dials under the front of the monitor to control focus and brightness. Alter them for personal preferences, but please return to original settings when done.
• All mice in the open lab have three buttons:

1. SELECT is the left mouse button, and is used in selecting items or pressing menu buttons.
2. ADJUST is the center mouse button, and is usually just for special programs.
3. MENU is the right mouse button, and is used primarily to pull down menus.

• Each SUN Workstation has a name. Workstations in the Open Workstation Laboratory are named "geog#", and are usually labeled on their monitors. It is important to know these names when asking for help or when trying to remotely access another machine. Complete names include a suffix, so that geog25's complete name is "geog25.umd.edu".

When ready to use, each SUN will display a login prompt. The GLUE login prompt is recognizable by its window, titled "Project Glue, Release 1.5". Under the title is the name of the University. Under the University title is a line to enter a userid. Under that is a line to enter a password. The login prompt will be on the screen whenever the machine is available for login. Do NOT attempt to login if the proper window is not available. An account must be active to be able to access it. If you are activating a new account, you will have a user name (userid) assigned to you and a temporary password. Use this password to log in the first time.

Type in the account username on the first line and press the Return/Enter key.

Type in the account password on the second line and press the Return/Enter key.

It will not be possible to see the password entered on the screen. An error message that reads "Login incorrect" indicates that the password has been entered incorrectly. An error message that reads, "You are not authorized to login to this machine" indicates that the userid is unknown or not authorized to use the workstation. Often, this is an indication that the userid was incorrectly entered, that the keys stuck, or that an invisible character was entered with the login. Try to login again and if it persists, get assistance.

Userids are the same name used for engineering or GLUE account (not WAM) email. In the Geography Department, userids consist of the first letter of the user's first name, and up to seven letters from their last name. To change your password, type and enter the command passwd in one of the X-term windows and follow the instructions. You will be prompted for your old password and then for your new password. When deciding on a new password, never use a word in the English language by itself for a password. Try to use symbol keys and/or numbers in addition to words, or just use symbol keys and/or numbers. Never use the following symbol keys: / * . , ~ and never use a space in passwords. Passwords should be at least six characters in length.

Be patient. If an account has been successfully entered, the screen may not change for a minute, depending on GLUE's traffic level. Do not try to login on another machine - be patient. If six minutes have passed without changes, tell an assistant.

A successful login will result in a standard screen. This screen will be the same with each login. Remember what a successfully accessed default screen looks like, unusual screens may indicate account problems. The standard screen will be in a window environment. This means that the screen will have at least one window open and available for command usage. There will also be a set of eight icons in the lower right corner, and the DASH-board on the top of the screen.

To log out, type and enter the command logout in an X-term window. Make sure you have closed all programs and ended all processes before you log out.

5.2 Navigating on the Screen:
 
If you are familiar with the graphic user interface (GUI) utilized by PC or Macintosh computers, the display and manipulation of windows on the screen in a UNIX environment will be readily understood. There is one major difference: UNIX uses a combination of a windows-type interface and a command-line interface. When you log in, you will notice that there will be one or two white windows (called "X-term windows") on the screen, along with a pull-down menu along the top (the Dash board), a set of 8 icons in the lower right corner (these may be covered by one of the X-term windows) and a small blue window in the lower left corner called the X-console. Any system error messages will be printed in the X-console.
 
The icons in the lower right corner serve a variety of functions. All of these buttons require only a single mouse click.  Multiple mouse clicks can cause several versions of the programs to be launched, or can cause the computer to freeze.
 
• The Xdir icon will launch a graphic display of the file system.
• A single-click on the Netscape icon will launch a Netscape browser window (be patient--sometimes Netscape requires a few moments to launch).
• The Music icon will launch the Motif CD Audio Payer.  If you have headphones, you may listen to music during regular Open Lab hours. However, it is important that you use the Motif CD control panel to operate the CD player. Using the buttons on the tower may result in the computer freezing. (Note that there is even an eject button on the control panel--DO NOT use the eject button on the tower.)
• The Xterm window will bring up a new X-term window.
• The Main and Misc icons are illustrating your position in what is actually a large desktop, essentially equal to eight screens. You can move between screens, and can perform different operations in each area of the desk top.
• Clicking the Xlock icon will lock your screen. To reactivate the screen, you must type your password. DO NOT use the X-term function on any of the Open Lab computers. If you have to leave the Open Lab for more than 15 minutes, you must log out. If you lock a computer station, that station will be restarted by a lab assistant so that other users may access it and you will lose all unsaved material.
 
You will run programs from the X-term windows by typing in commands to start a program. Each X-term window will run one program, and you can have multiple programs running at the same time. For example, you can run Pine in one X-term to monitor your e-mail, you can run ArcView out of another X-term to work on a project for class, and you can run Pico, a text editing program, in a third window to take notes about what you are doing in ArcView. In order to type in the necessary commands, the X-term must be activated. You can activate an X-term simply by placing the mouse cursor inside it. The bar at the top of the X-term lights up when it is activated. X-term windows can be resized by grabbing the corner with the mouse and stretching it to the desired size, they can be minimized by clicking on the minimize button in its upper right corner, and they can be closed, either by typing "exit" at the command line or by clicking the "X" in the upper right corner.
 
All windows can be minimized in the same manner as an X-term window. When a window is minimized, it will appear as an icon in the lower left corner of the screen, usually under the X-console window. To maximize the windows again, simply move the X-console out of the way and double-click on the icon. All windows can also be "folded up" into the blue bar at the top of each window by clicking on the blue bar with the middle mouse button. The blue title bar will remain on the screen, but the window will disappear. To "unfold" the window, middle-click on the blue bar again. All windows can be moved by grabbing the blue bar with the left mouse button, and resized by grabbing the corner of the windows with the left mouse button. Several windows may end up on top of each other. To pull the back window to the front of the others, simply press the left mouse button on the window's border and it will come to the front of the screen. If an hourglass symbol is where the pointer should be, the user cannot do anything else in that window. The hourglass indicates that something is working in the window, and the user should wait. Other windows which do not have the hourglass symbol will be available for use while the other window is busy.


5.3 About Your Glue Account:

Not all Glue accounts are the same. The Engineering Department sets up accounts to function for specific reasons, usually either for general use or for certain classes. The Geography Department also sets up its own accounts for various reasons. You must have an account through the Geography to use the Open Lab workstations.

The default account space is called the home directory. This space is where the user automatically ends upon login. If the user is located elsewhere on the system, get to the home directory by typing and entering in an X-term window:

cd /homes/userid
(The "cd" command allows you to change directories).

or

cd ~
(The "~" is shorthand for "/homes/userid".)

or simply

cd

You will learn more about the UNIX file structure and navigating through directories in the Basic UNIX section.

GLUE home accounts are usually 25 megabytes in size. It is important to learn to manage your files so that you do not exceed your allotted space. To check the quota in your homespace, type and enter:

quota

When you enter this command, you will be notified of how much of your homespace is in use and how much is free. If the account quota has been exceeded, the user will be given a temporary home space in which they may delete or move files in order to free quota space.

A class that uses the UNIX system in the Geography Department may be assigned disk space for the duration of the class. These disk spaces are usually between 25 and 50 megabytes. The instructor or TA will inform students about space for course work, but it is important that you do not exceed the quota allotted to you for class work. To check your class space quota, you must first change directories into the class space and then type and enter:

quota -v

To log out of an account (end the UNIX session), first make sure that you have closed out of all programs and processes. Then perform one of the following:
 
1. type "logout" and The Return/Enter key on any xterm, OR
2. pull down and release the DASH menu choice, Special=Logout. Be sure to wait and answer any secondary windows that confirm if the user really wants to log out. The GLUE login prompt will appear after a successful logout.


5.4 The Dash Board:
 

The white strip at the top of the screen is the Dash Board, which contains several menu choices, from Help to Quick!. Also on this line, in the upper right corner, is the current system time and date. Most of the processes that can be chosen from this menu can also be directly accessed by entering the proper commands in an X-term window. Press a mouse button on any of the Dash choices to pull down the menus of further choices. To select and start a menu choice, release the mouse button over the text of the choice.
• Follow arrows to the right of the pull-down menus to pull down a further menu.
• A question mark (?) on the menu indicates that a short textual description about the choice is available if the mouse pointer is positioned on top of the ? symbol.
• A "*" next to a Dash selection indicates that it is an executable file.
Note that the Dash can be dismissed by using the DASH=Hide Menus choice on the left end of the menu. Also, Dash can be started by typing "dash" at the UNIX prompt in an X-term window.
 
The following is a brief outline of Dash selections. Dash Help provides information on how to get help, as well as executable commands to begin the process of retrieving help. Some of these commands are particular to GLUE.
• "On Line Documentation" contains brief documentation for several different system packages, all of which are available in printed form at the Computer Center. Of particular note and usefulness is the AFS Beginner's Guide.
• The "xman" option offers on-line help about UNIX.
• Utilities contains choices for screen display, including windows. If the mouse button is released on the Utilities=Window=Default Window the user will receive a new xterm window on the screen.
• Applications allows the user to "tap" software packages to enable their use.
• Internet provides access to e-mail, news, ftp, mosaic, InforM, Mosaic, Victor, etc.
• Text provides access to text editors or word processors.
• Graphics provides access to graphic picture editors and display software.
• Numerical offers mathematical and statistical software, as well as spreadsheets.
• Programming starts different programming language sessions.
• Logins allows access to other machines around campus.
• Special is special. Under this menu, the user can log out of an account by releasing over "Logout". It is crucial to wait for the second window that asks "Do you really want to logout?". When the second window pops up, press once in the Yes or No box to actually log out of the account.


5.5 Commonly Used Dash Options:
 

The following is a list of the DASH options that are frequently used in the Geography department.
• Help=OnLine Documentation=AFS Beginners Guide - produces a ghostview document of AFS instructions.
• Utilities=Windows=Default Window - produces an Xterm window.
• Utilities=Calculators=Xcalc - produces a calculator.
• Utilities=Print=Print Window - prints whatever is in the selected window.
• Utilities=Xview=Cmdtool - produces a command tool window.
• Applications=Tap=a-e=arc - taps ARC/INFO and ArcView.
• Applications=Tap=f-l=island - taps Island software.
• Applications=Tap=m-p=pci - taps PCI software.
• Applications=Tap=q-z=splus - taps S-Plus software.
• Graphics=Picture Display=xv - produces a XV window for image display.
• Logins=Telnet - provides remote access to other computers through Telnet.
• Special=Logout - logout from the UNIX session.


5.6 Copy/Paste Operations:
 

The manner of taking text from one window and putting it elsewhere, either inside the same window or in another, is called a cut (or copy) and paste operation. The operation usually begins by selecting a group of text by pressing the left mouse button and dragging the pointer across the screen. This activity should result in the selected area having a black background. To paste the text into another window, place the mouse cursor in the desired location and press the middle mouse button. You should be able to copy and paste between and within most windows, even if they are not the same program (i.e. you can copy text from a Netscape window and paste it into a Pico window or into a WordPerfect window).

6.2 UNIX File Structure:
 
UNIX stores data in files. Files may be simple text, complex images, programs, etc.; each file has its own filename. UNIX stores files in directories. Each directory will have its own name, and a forward-leaning slash "/" at the end of a name. Please note that this UNIX slash (/) is the opposite of the DOS backward- leaning slash (\). See the file manager under the Dash Utilities=Xview=filemgr for a full hierarchical breakdown of all files and directories. Also, UNIX stores directories inside other directories. A directory that exists within another directory is called a subdirectory. It may help to visualize the hierarchy as a tree's root system, with the top of the hierarchy at ground level, with a single trunk. Subdirectories branch out from here, forming more and more subdirectories the further down the hierarchy that is traveled. At the ends of branching roots, the root tips are the files and empty subdirectories.

Learn to recognize files and directories. This is important for examining data. A text file cannot be entered, but a directory can. A directory cannot be opened and displayed in a text editor, but a text file can. Directories are usually listed with a forward slash after their names. Files will only have their names, with periods or dashes separating parts of names. Filenames will also usually be followed by an extension that indicates the type of file it is. For example, filename.txt is an ASCII text file, filename.doc is a WordPerfect file, filename.ps is a postscript file, filename.exe is an executable program file, etc.

Learn UNIX directory nomenclature. A path name is the full name of any directory or file on the system. Type ls in an X-term window to receive a listing of all the files and subdirectories in the present working directory. That current directory, however, is inside other directories. The order of path names puts the highest position on the hierarchy to the far left, moving to the right while descending through the hierarchy to the current directory. For example the path name "/top/middle/low/currentdirectory" illustrates where the current directory actually resides on the system. See the commands "pwd" and "cd" below.
 

6.3 Basic UNIX Commands:
 
The commands listed below are common UNIX commands and should provide you with enough information to navigate through your UNIX account.  Commands listed below will be in bold, and examples of the command usage will be in italics. UNIX is case sensitive. Always press Return/Enter to activate the command that has been typed on the screen (some keyboards have an "enter" and some have a "return" key). Always use lower case, except when specifically told to use upper case. UNIX files and directories can have any name, with certain exceptions. Do not use a space, *  ! ,  ~  |  & or / inside a name. Names can be any length, but remember how long it takes to type long names. UNIX commands can be entered in any X-term window. Some command-line software that operates in UNIX will take UNIX commands at the software prompt, but usually software will only allow that software's specific commands (such as ArcInfo).

You can use the on-line help for each UNIX command. Using the "man" (on-line manual) system on any UNIX command will provide all the command's options and some documentation. Manual pages are also available under the DASH Help=xman option or by typing and entering man command in an X-term window. To exit a "man" window, press the Escape key twice or press "q". To page down, use the space bar. To page backward, press "b".

cd Change Directory; use this command to change from one directory to another.
cd directoryname or cd /homes/username/stuff

cp Copy a file. cp filenameold filenamenew

du Directory or disk usage; lists usage on a disk or directory. du directoryname, or simply typing du will list all files and folder and their size.

finger Allows you to see if another user is logged on to the network. finger username

less List a file's contents on a screen by screen basis, necessary for larger files. Use only for ascii files. Allows the user to go backwards and forwards within the file. less filename

ls List all the non-hidden files in the current directory ls or ls subdirectoryname.

ls *.filetype List all files of a certain type. ls *.txt

ll List all hidden and non-hidden files in the current directory ll or ll asubdirectoryname

mkdir Make a new directory (will be a subdirectory in the current workspace). mkdir newdirectoryname

more List a file's contents on a screen by screen basis. Necessary for larger files. Similar to "page"; use only on ascii files. more filename

mv Change (move) a file's name to something new. mv oldfilename newfilename

passwd Changes the user's password. Follow the instructions after entering command.

pwd Print working directory to screen. Tells you where you are on the system.

qcheck Prints to screen the status of the print queue (on qpr printers). qcheck printername

qmod Modify the status of the print queue (on qpr printers), usually to kill the user's print job. Usually used after "qcheck". qmod -k printjobnumber

qpr -q Prints an ascii text file or a postcript file to the printer. qpr -q printername filename. Since the Open Lab computers are on the campus-wide pay-per-print system, you would need to expand on this command to specify the amount of money, in cents, required to print the document. qpr -q printername -m cents filename

rm Removes files and links. Be very careful with the powerful options (check with "man"). There is no undo command in UNIX, or software to restore accidentally erased files. rm filename

rmdir Removes a directory. Make sure you want to do this. rmdir directoryname
 
 

6.4 Intermediate UNIX Commands:
 
alias Creates a file to run specified command(s). These alias files are stored elsewhere. alias aliasname command(s)

chfn Changes the user's "finger" information.

chmod Changes the user mode, or ownership, of files and/or directories. chmod 700 filename OR chmod -w filename or see section 4, access control, in the AFS Beginner's Guide.

clear Clears the window screen.

exit Exits any jobs running in a window and closes the window.

file Identifies the type of file. Ascii and postscript are most common text files. file filename

fs listquota Prints the user's disk space quota. Works only for AFS. fs listquota

ghostview A program that allows the user to check postscript file formats prior to printing. ghostview filename

kill Kills any job specified. Usually used after using "ps". kill -9 job#  (See top).

kinit Reinitialized the Kerberos tickets, required the user to re-enter the userid and password.

ld Lists only the subdirectories in the current directory.

man Prints to screen the manual pages regarding the specified command.

rlogin Remote login to a machine other than the one being used. Similar to telnet. rlogin geog25

rm -r Allows the user to recursively delete files and directories. rm -r directoryname

tap Taps into the network software library to access a certain software package. It is necessary to "tap" before starting the Arc/Info, PCI, and S-Plus software. tap programname

telnet Remote login to a machine other than the one being used. Similar to "rlogin", but requires the username and password. telnet geog25

top Lists all processes running on the workstation. Each process is identified by a process identification number. top

wc Word count of an ascii file. wc filename

whoami Prints to screen the userids of everyone logged on to the current station.
 

6.5 Special UNIX Command Operations:
 
• A command can be entered by itself (if it has options) to get a list of options. For example, entering "tap" by itself will not actually tap into a software package, but entering the command by itself will provide a list of all possible tap options.
• "|" is called a pipe in UNIX. Using this character will allow for the combination of two command operations on one line; it sends the results of one command to another command. For example, to list the contents of a directory that would fill up more than one screen, use the "more" command to give the listing page by page: ls | more
• "*" is the UNIX wildcard. To list all files in the current directory beginning with a "c": ls c*  You can also list all files that have the same name, but with different extensions: ls filename.* Be very careful using this, as it has the potential for disaster when using it with the rm command. Typing rm * will remove all files without an extension, rm *.* will remove all files with an extension.
• "." is the UNIX abbreviated name of the current directory. To copy all files from a remote directory to the current directory (notice a space between the "*" and the "."): cp  /remotedirectory/*   .
• To repeat previously used commands, press the up-arrow key.
• To put the output of a file listing into an ascii file: ls filename
• "~" is the UNIX abbreviated name of the user's home directory. Use the "~" to shorten typing requirements. This key is called the "tilde". ls ~/subdirectory
• grep provides the ability to find strings in files. For example, to find all the locations of the word "key" in directory files and subdirectories whose names begin with "how": grep 'key' how*
• cd can be used by itself to return to the home directory. Also, the following version of the "cd" command will relocate the user to the next higher directory in a directory hierarchy: cd  ..
• chmod is useful for changing the permissions of files and/or directories. To see current permissions for files, use "ll". Using the long option of the list command provides a list with each file and directory on separate lines. Each entry will have some r,w,and x's at the beginning of their line. R stands for read permission, w for write, and x for execute. A dash symbol (-) indicates that the option is closed. The d indicates if the line represents a directory, and is the only option for the first character in the line. For instance: -rwxrwxrwx or drwxr-xr-x The next three characters represent the user's permissions, followed by the three characters for the group permissions, and finally the last three characters for the world permissions. To use a file, the user will want to be able to read, write, and execute the file. To have the file available for others in the network's group to have access for reading but not writing or executing, then set the permissions to prevent anything but reading. Read the "man" pages for all the options. To make a file or directory have permissions for only the user to execute and write, but for the group and world to read only, enter the following: chmod 744 filename or chmod -w filename. To make a file available only to the user: chmod 700 filename
• kill is useful for killing processes, or the entire session. If the user is logged in and has been able to operate in windows but can no longer get anything to work on the workstation, then the machine is probably hung up. Check to make sure that the mouse and keyboard cable are fully plugged in. Find a lab assistant if everything remains frozen. If a lab assistant is not available, try the following: log in on another machine, and telnet to the machine that is hung. Login and use an xterm to enter the following: top. This command will list all processes that are active on the hung machine. Notice the numbers that indicate the process job, and a brief coded message with the process name. To kill all processes on the hung machine, terminating everything and logging out, find the process number for something named /bin/bash /local/lib/xdm/Xsession. The process number (#) is in a column named PID (Process Identification). Enter the following to log out of the account: kill -9 # If you know which process hung up the machine, then kill that particular process job, using the same syntax as above. Otherwise, killing the /bin/bash /local/lib/xdm/Xsession process will log the user out of the account.
• ln provides the means to simplify changing directories. If a directory that takes a long time to type in is frequently used, try this short-cut. If the very long path name for the directory in question is "/a/very/long/name/to/have/to/type/every/time/it/is/necessary/to/use/it", then try the following: ln -s /a/very/long/name/to/have/to/type/every/time/it/is/necessary/to/use/it long This creates a link named "long" in the current directory. It should look like "long@" in the directory listing. Now instead of typing cd /a/very/long/name/to/have/to/type/every/time/you/want/to/use/it in order to change to that directory, it is only necessary to type cd long to end up in the directory /a/very/long/name/to/have/to/type/every/time/it/is/necessary/to/use/it.

7.1 WHERE TO GET HELP

On-line help is available to all users in the following manners:

1. Off the DASH-board, under the Help selection:
• xman = menu driven manual of UNIX commands; Use the "Search" option for specific commands.
• xinfo = menu driven manual for UNIX network information. (X information)
• On-Line Help = menu driven guide to GLUE information.
• On-Line Documentation = files written for GLUE users about available programs.
• InterViews help -Request
2. At the UNIX prompt, in any xterm or command tool window: -man -xman
3. Glue On-line Help (http://www.glue.umd.edu/afs/glue.umd.edu/system/info/olh/)

Help is also available from these non-line sources:
• manuals, including the UNIX For Dummies books, available in Lefrak 1124
• on-duty assistants
• The Computer Science Center's support line is available by calling 405-1500.