CS 279 - Week 2 Lecture 1 - 8-28-12

Chapter 2 - UNIX Basic Concepts/Fundamentals

*   use the echo command to send the value of its expression
    to standard output

echo "Howdy"
Howdy
echo "Howdy" > boo
...boo now is a file with that text...

(ref: Chapter 2 of "UNIX for the Impatient")

*   system administration (in UNIX/Linux world) is a 
    collection of tasks whose purpose is to make
    the UNIX system available to its users in an
    orderly and secure manner

*   who can system administration tasks?
    the superuser (or superusers)

    ...the programs/files for system administration
    are accessible only to specially-designated user(s)
    called the superuser

    *   the special user name for the superuser: root

    *   whoever knows the password for the root account
        CAN act as superuser...

    *   initial password for root is set
        as part of the process of installing a system;
	then the ability to be superuser is given
	by making that password (carefully!) available

*   IN GENERAL, to USE a UNIX system, you must be
    registered as one of its users -- you need a user
    account on that system

    each user on a UNIX system has a login name,
    a password, and an area of the file system
    reserved for storing his/her files

*   permissions in UNIX in general are based on 3
    levels: owner level, group level, and world level

    (world really means everyone with an account on that
    machine)

*   environment variables are UNIX shell variables
    that hold useful information...

    ...note that shell variables (in bash) start
    with a $ sign

    $SHELL - holds your login shell
    $0 - holds your current shell (really the currently-
         running shell)

*   the UNIX kernel
    *   heart of the OS!
    *   controls access to the computer and its files,
        allocates resources among the various activities
            taking place within the computer,
        maintains the file system, and
	manages the computer's memory

*   the activities taking place within a UNIX system
    are called processes

*   ps command: process status

*   daemon: a system process that "reside[s] in the system more or less
    permanently and perform ongoing tasks...."