Introduction to Unix

1
Introduction to Unix

• Brian C. Hoffman
• CINS 142

2
What is an Operating System?

• The operating manages computer resources
• Schedules processes for the CPU
• Manages memory
• Schedules hardware I/O
• Interfaces with the hardware
• Acts as a control program
• Provides security
• Traps errors
• Decides what process run and with what resources
• Provides an interface to the user
• Provides a means for running applications
• Shields user from complex hardware details
• Makes computer efficient and convenient to use

3
Growth of Operating Systems

• 1950s - No OS
• you configured the hardware to perform the
  desired task.
• 1960s - Mainframe systems
• Started with batch processing in which computer
  ran one task at a time
• Advanced to multiprogramming in which multiple
  processes would run concurrently. You would
  switch between them as you need to do slower IO
  tasks.
• 1970s - Timesharing
• The computer servers multiple users and each user
  gets a slice of the CPUs time. CPU switched so
  fast each user thinks they are the only one.
• 1980s PCs
• Only one user so you could be less concerned
  about efficiency and more concerned about
  convenience.

4
History of Unix

• Developed in 1969 at ATT Bell Labs by Ken
  Thompson and Dennis Richie
• In 1973, they rewrote it in C. It was unusual to
  write an OS in a high-level language. This made
  UNIX very portable.
• US Government prevented ATT from selling
  computers so the system was distributed to
  academic institutions.
• It was improved significantly at the University
  of California at Berkley
• BSD Unix
• Created vi, C shell, symbolic linking, a better
  file system, and TCP/IP
• Other corporations started developing their own
  versions
• For more information, see http//www.unix-systems.
  org/what_is_unix/history_timeline.html

5
Unix Variants

• BSD, Free BSD from Berkley Software Design
• SunOS and Solaris from Sun Microsystems
• AIX from IBM
• Ultrix from DEC
• IRIX from Silicon Graphics
• UnixWare and Open Server from Santa Cruz
  Operation (SCO)
• Linux and other Open Source variants

6
Why Unix and not Windows?

• Unix is a very powerful multi-tasking OS capable
  of using the power of modern computers.
• Unix was built as a multi-user OS from the ground
  up and includes strong user security and control.
• Unix has numerous variants and is portable across
  systems.
• Unix is a powerful programming environment. It
  was written in C and includes a great deal of
  support. Also, most unix shells are programmable.
• TCP/IP was implemented in BSD Unix well before
  MS-DOS even existed. Thus, Unix has excellent
  networking support.
• The File System is very powerful. It does not
  type files and has tons of unilities for working
  with them.

7
Why not to use Unix?

• Many programs such as MS Word that are commonly
  used are not available in Unix.
• Unix uses terse text based commands with lots of
  options. For example, ls has 24 options.
• Unix is unforgiving. It gives you a lot of power,
  but if you delete a file or mess up settings, it
  can be hard to fix.

8
Inside Unix - Its Components

• Kernel
• The kernel is the one process that is always
  running.
• The kernel interacts with the hardware and does
  most of the OS system tasks
• Provides an API via which applications can make
  use of system resources. The API takes the form
  of system calls
• Shell
• The Shell interacts with the user and process
  commands
• Utilities
• Unix provides a number of utilities that allow
  the user to perform tasks without having to write
  code or know system calls

9
Your Unix Account

• Your account exists on student.ccbcmd.edu, the
  student unix and web server.
• You will access the account via telnet, an
  application for logging into a remote computer.
• Execute startgtrun in the task bar.
• Type telnet into the dialogue box that opens.
• You will get a command window. Type o
  student.ccbcmd.edu to open a connection.
• When prompted for your username and password,
  enter them based on the provided sheet.
• When prompted for a terminal type, enter vt100.

10
Changing Your Password

• Enter passwd at the provided propt
• It will ask for your old password, enter it.
• It will now ask you for your new password. Enter
  it.
• Finally, it will ask you to enter it again for
  conformation.

11
Password Guidelines

• Do not use words from the dictionary, literature,
  or common variants such as replacing an e by 3.
• Do not use easily guessed personal information.
• Mix upper and lower case.
• Do not use repeating patterns.
• Include characters other that letters.
• Use 6-8 characters. The more, the better.
• If you forget your password see Judith Woke in
  room D 111.