Components

  • boot system;
    BIOS looks for the first floppy disk sector or MBR (Master Boot Record)
    LILO
  • kernel;
    one file (vmlinuz or zImage, bzImage ..) + modules
    device diagnostics
    mount the main file system (root)
    Initialization of the system (init)
  • file system;
    Just a unique file system
    Mounting
    Mounting points

  • process initialization and management system;
    Multitasking
    init
    daemons or servers
  • network management;
    Networks services are managed mainly by 3 daemons:
    • inetd that starts, when is needed, the required service;
    • tcpd controls and filters access to services;
    • rpc.portmap (or just portmap) that handles RPC protocol(Remote Procedure Call).
  • printer management;
    spooling
    lpr
    remote printing
  • accounting and logging facilities;
    Multiuser
    Registration using an account and password
    login
    logout
  • shell (command interpreter);
    interaction between user and operative system
    many shells: bash, csh, tcsh ..
    shell duties:
    • shows the prompt, means ready to receive commands;
    • handles parsing of command line typed by user ;
    • executes instructions, taking into account wild chars (globbing) and environment variable;(1)
    • allows use of some internal commands;
    • executes programs;
    • handles input and output redirections;
    • can parse and execute files containing commands (shell script files).
  • (utility) to manage the system;
    Small files contained in /bin/ and /usr/bin/
    Used only by the administrator /sbin/ and /usr/sbin/
  • software development tools