Computing at UMBC An Introduction to the UMBC Computing Environment

1
Computing at UMBCAn Introduction to the UMBC
Computing Environment

• CMSC 121 Introduction to UNIX
• Much of the material in these slides was taken
  from
• Dan Hoods CMSC 121 Lecture Notes.

2
Your GL Account

• GL is short for General Labs. Through this
  account you have access to various computing
  resources across the campus.
• Your GL Account gives you access to
• Many labs that are maintained by OIT. An listing
  of these labs can be found at http//www.umbc.edu/
  oit/classroomtechnology/labs/lablocation.html.
  These labs contain an assortment of dual-bootable
  Windows 2000 / Linux PCs, Macintosh's, and
  several IRIX machines.
• You also get remote server access to several UNIX
  machines...
• linux1.gl.umbc.edu, linux2.gl.umbc.edu,
  linux3.gl.umbc.edu
• irix1.gl.umbc.edu, irix2.gl.umbc.edu
• solaris.gl.umbc.edu
• The username and password on this account are
  also your username and password for
  http//my.umbc.edu/.
• Your username is also your e-mail name. You get
  an e-mail account automatically when you sign up
  for a GL account. It is username_at_umbc.edu, where
  username is your logon name.

3
Your E-mail Account

• Can I change my e-mail address?
• Technically no, but you can create multiple
  aliases that send mail to username_at_gl.umbc.edu.
  In effect, this changes your e-mail address.
• To set up e-mail aliases, follow the instructions
  at http//www.umbc.edu/oit/sans/helpdesk/alias.htm
  l.
• You can also set up your e-mail to be forwarded
  to another account if you wish. See
  http//www.umbc.edu/oit/sans/helpdesk/acctforward.
  html for more details.
• Sending and Receiving E-mail. There are lots of
  ways to do this!
• Pine - a UNIX, text-based e-mail client.
• Netscape / Mozilla / Outlook - bulky clients,
  graphical. See http//www.umbc.edu/oit/sans/helpde
  sk/configuremail.html.
• Webmail - UMBC's web-based e-mail client. Its
  fast, easy-to-use, and accessible from anywhere.
  http//webmail.umbc.edu. There is also a webmail
  tutorial http//www.umbc.edu/oit/sans/helpdesk/em
  ail/webmail/.
• It is strongly suggested that all CS students
  lean the Pine e-mail program. It is very easy to
  check your mail remotely via ssh, rip in source
  code, and is very quick and easy to use (well,
  once you get used to it). We strongly feel that
  it is so important that a whole class will be
  dedicated to Pine and Pico.

4
The Andrew File System (AFS)

• AFS is distributed network file system.
• A file system is simply a collection of files and
  directories assembled in such an order that the
  make sense to the operating system.
• AFS is a way of keeping track of your files over
  the network.
• Features
• You can access your files using any computer that
  has an AFS client installed on it.
• All of the lab computers Windows, Linux, IRIX,
  and Mac, are capable of reading this file system.
• The files that you maintain in your account will
  be accessible to you over the network from any of
  these computers. No need to store your
  information on a flash drive and carry it between
  machines.

5
Your Directory on AFS

• Every GL account is assigned a directory on AFS,
  which contains the home directory, web space, and
  e-mail folders. On all of the UNIX systems here
  at UMBC it will be located at the following
  location
• /afs/umbc.edu/users/u/s/username/
• u is the first letter of your username,
• s is the second letter of your username,
• and username is your GL account logon name.

6
Contents of Your AFS Directory

• These are the folders that are in your account at
  the time of creation
• home - your UNIX home directory.
• Mail - this is where all of your e-mail files are
  kept.
• pub - this is where public data can be placed,
  including web space.
• backup - this is a backup copy of your
  /afs/umbc.edu/users/u/s/username/, updated
  nightly.
• Within the home directory
• All of the typical files found in any UNIX
  environment (.cshrc, .login, etc...)
• Windows NT and 2000 Profiles (.2kprofile and
  .ntprofile directories)
• Your files!
• Within the Mail directory
• files for all of your mailboxes (inbox,
  sent-mail, etc...)
• certain configuration files (such as .forward,
  .procmailrc, etc...) that allow you to manipulate
  your mail.
• For example, forwarding you mail to another
  account, or filtering your incoming email.

7
Contents of Your AFS Directory

• Within the pub directory
• it is empty by default!
• This is where you can put files, so that others
  can readily copy them from here into their
  accounts.
• You can also have a www directory within your pub
  directory that allows you to post files onto the
  Internet, accessible via http//userpages.umbc.edu
  /username/
• The backup directory
• is a copy of your entire account, that is
  read-only and taken from the night before. This
  is typically done around midnight.
• If you were to accidentally delete a file (or
  screw up a source code file so it no longer
  compiles) that you had around yesterday you can
  go into this directory and you will be presented
  with the home, Mail pub directories from the
  day before. You can then simply copy the file
  from here to wherever you want.

8
Getting to Your Files

• You should usually save files to your home
  directory (/afs/umbc.edu/users/u/s/username/home/)
  . How you access your home directory depends on
  the operating system
• UNIX / Linux - your home directory is available
  to you under the /afs/umbc.edu/users/u/s/username/
  home/ directory. Almost all UNIX shells will
  start you out in this directory by default.
• Windows
• Your directory (/afs/umbc.edu/users/u/s/username/)
  is mapped as the network drive "T" on the
  Windows PCs.
• Your home directory (/afs/umbc.edu/users/u/s/usern
  ame/home/) is mapped as the network drive "S".
• If you have a www directory in your pub directory
  (/afs/umbc.edu/users/u/s/username/pub/www/), it
  is mapped as the network drive "W".

9
Changing Your Password

• Via the Web
• Logon to http//my.umbc.edu, click on the
  Personal tab, then click on Change my Password.
• Follow the on-screen instructions for changing
  your password (there are several steps).
• Via the UNIX Command Prompt
• The standard way to change your password on most
  all UNIX systems is through a text-based shell.
• To change your password this way, you will need
  to have shell or terminal access to one of the GL
  UNIX machines. This can be in the form of a shell
  on one of the dual-boot lab machines, or by way
  of remote SSH access.
• Once you have your shell open, type passwd at the
  command prompt.

10
Changing Your Password

• linux1-(1123am) passwd
• passwd Changing password for eeaton1_at_UMBC.EDU.
• Old password
• New password
• New password (again)
• Kerberos password changed.
• linux1-(1124am)

• Note that when you type your password, it will
  not be echoed to the screen, not even asterisks
  ().
• Windows?
• You may be inclined to change your password by
  pressing Ctrl-Alt-Delete and choosing the "Change
  Password" option.
• But this has been disabled here in the GL labs at
  UMBC.

11
If Someone Knows Your Password

• Change it NOW!!!
• Your GL password is just that - yours and only
  yours. You should not share it with anyone.
• If you think someone knows your password. Here is
  what you should do...
• Change your password immediately.
• Report this incident to helpdesk_at_umbc.edu. OIT
  keeps a log of all activities in all UNIX
  accounts. Any unauthorized access can be tracked
  given ample research time.
• You are legally liable for any action caused
  under your account.

12
Choosing a Good Password

• OIT has suggested the following guidelines for
  choosing a good password...
• Passwords should contain at least
• 7-14 characters
• 2 numbers or symbols in the first 8 characters
• 5 different characters (letters, numbers,
  symbols)
• Passwords should not contain
• The at sign ( _at_ ), the number sign ( ), or the
  ampersand ( )
• Doubled numbers or symbols (e.g., 99 or )
• Any words or names spelled forwards, backwards,
  or in a foreign language
• A Social Security number in the first nine
  characters of the password
• Words constructed with similar-looking number
  substitutions (e.g., 0 for O for S 1 for i
  ), for example capta1nk1rk, mr5p0ck
• Note Passwords are case sensitive. The lowercase
  c is a different letter from the uppercase C
  . Make sure that the Caps Lock key is not on,
  unless you intend to enter all uppercase letters.
• If you forget your password, the OIT helpdesk can
  reset it for you.

13
Your Quota

• Every student on the GL network has a set disk
  quota. This is the amount of space given to most
  students is 25 MB. That is not a lot of storage
  space! So, some effort must be made on your part
  not to exceed this disk quota.
• Everything that you store in your directory
  (/afs/umbc.edu/users/u/s/username/) counts
  towards this 25 MB limit with the exception of
  your backup directory, which not figured into how
  much space you are using.
• Exceeding your disk quota can cause any number of
  problems
• Lost email messages
• Inability to compile programs
• Abnormal account behavior
• To check your usage and overall quota, type quota
  -v in a UNIX shell. If you are exceeding your
  quota, change your browser settings so they cache
  little (or nothing at all) to disk. You may then
  have to manually delete the cached files. If you
  need help with this, see an OIT Help Desk
  consultant.
• For more information on how to check your quota,
  see http//www.umbc.edu/oit/sans/helpdesk/afs/afs_
  disk_quota.htm.

14
Checking Your Quota

• Type in the quota -v UNIX command at the command
  line.
• Your output should look something like
• Doin just fine.
• Nearing the limit.
• Over the limit. Danger zone.

linux1-(1220pm) quota v Volume
Name Quota Used Used Partition user.dhood2
75000 59158 79 64
linux1-(1220pm) quota v Volume
Name Quota Used Used Partition user.dhood2
75000 70754 94ltlt 64 ltltWARNING
linux1-(1220pm) quota v Volume
Name Quota Used Used Partition user.dhood2 75000
75798 101ltlt 64 ltltWARNING
15
How to Get Back Under Quota

• OIT has made available a tool that goes through
  your account and tries to eliminate unnecessary
  files and very large files that may be putting
  you over the limit.
• You can issue the oitcleaner command...
• Note that the latter part of this script tries
  to remove larger files that are in your account.
  You have to answer "y" or "n" whether or not you
  want to remove these files.
• You can also make sure that you have set up the
  web browser to cache as little as possible to
  disk.

16
Restoring a Lost File

• Remember the backup directory only contains a
  copy of all of your files from the night before.
• If you need to restore a file that you deleted
  days ago, or just minutes ago (assuming minutes
  ago was still today), then you are not going to
  find the file here.
• If it is really important and it was in your
  account overnight for at least one of these
  backups, than you may be able to have OIT see if
  they can recover the file for you.
• Note that this is only done in the rarest and
  most dire circumstances.
• In-class demo of recovering a file, both
  graphically and from the console.

17
The Outlaws Telnet and FTP

• Telnet and FTP refer to basic network utilities
  (and related protocols) that allows a user to
  interact with a remote host using a text-based
  virtual terminal.
• Telnet and FTP are both widespread (they are
  integrated into many operating systems) and
  useful.
• You may have telnetted from your home Windows PC
  to a UMBC Unix server to check your email with
  Pine, or transferred files between 2 computers
  using FTP.
• What is wrong with them?
• Telnet and FTP are inherently insecure.
• When you initiate a telnet or FTP connection,
  your username, password and other bits of
  important information are broadcast in cleartext,
  meaning that they are visible to anyone located
  between your computer and the intended server
  destination.
• For example, any curious person with a
  802.11b-equipped laptop, a packet sniffer program
  (designed to intercept and interpret data
  broadcast across a network), and a rudimentary
  grasp of networking could sit within range of
  UMBC's wireless networks and grab any usernames
  and passwords transmitted in cleartext.
• Regardless of where and how you're online, if you
  use telnet or FTP, you're putting your vital data
  at risk.
• Because of the vulnerabilities associated with
  telnet, UMBC's Office of Information Technology
  (OIT) prohibited telnet connections to UMBC
  servers beginning in January 2003.

18
SSH (instead of Telnet)

• SSH stands for Secure SHell.
• It provides terminal or shell access to some
  remote computer.
• SSH can be viewed as nothing more than a secure
  version of telnet.
• There are several SSH clients to choose from.
  Some are installed in the OIT labs, some you can
  install, and others require administrator
  privileges that you may not have under Windows
  (at least in the labs).
• Tera Term Pro (available in the UMBC labs)
• Putty http//www.chiark.greenend.org.uk/sgtatham
  /putty/

19
SCP (instead of FTP)

• SCP stands for Secure CoPy.
• It provides the functionality of a File Transfer
  Protocol (FTP) client.
• SCP can be viewed as nothing more than a secure
  version of FTP.
• Again there are many SCP clients out there
• WinSCP (available in the labs)
  http//winscp.vse.cz/eng/
• The Linux command
• scp localfile username_at_gl.umbc.edu/path/filename
  

20
Open AFS

• AFS is a distributed file system, pioneered at
  Carnegie Mellon University and supported and
  developed as a product by Transarc Corporation
  (now IBM Pittsburgh Labs). It offers a
  client-server architecture for file sharing,
  providing location independence, scalability and
  transparent migration capabilities for data.
• IBM branched the source of the AFS product, and
  made a copy of the source available for community
  development and maintenance. They called the
  release OpenAFS.
• Mounting your UMBC AFS Directory at Home
• Download and install the windows Open AFS client.
  During installation you will be prompted for an
  AFS cell name, you should enter umbc.edu
• When the installation is complete, you will need
  to reboot. After you reboot, there will be an
  icon that looks like a lock in the system tray.
  Click on this to launch the OpenAFS dialog.
• Under the Tokens tab, click Obtain New Tokens...
• Be sure that the cell name is umbc.edu and go
  ahead and enter your username and password, then
  press enter. If everything went ok, you should
  see an entry under tokens with your GL username.
• Under the Drive Letters tab, click Add...
• Chose an unused drive letter, and enter the path
  to your root directory on GL (/afs/umbc.edu/users/
  u/s/username/), and click enter. If everything
  went ok, then you should see the drive letter
  added under the OpenAFS dialog.
• You should now be able to browse the drive in
  Windows Explorer.