SA class 2

Kernel and Shell

Hardware => kernel => shell => you

shell: +-=> Fetch command => analyze => execute -+
       |                                                                         |
       +-----------------------------------------------------------------+

startup files

sh
    /etc/profile        login shell, system wide
    ~/.profile          login shell
    ENV                 always

csh
    /etc/csh.cshrc      always , system wide
    /etc/csh.login      login shell, system wide
    ~/.cshrc            always
    ~/.login            login shell
    ~/.logout           logout shell
    /etc/csh.logout     logout shell, system wide

tcsh
    ~/.tcshrc  login shell

bash
    /etc/profile
    ~/.bash_profile
    ~/.bash_login
    ~/.profile
    ~/.bashrc
    BASH_ENV

Shell special characters
Reduce typin as as possible, be lazy zzZ
    *      Match any string of characters
    ?      Match any single alohanumeric characters
    [...]  Match any single char within []
    [!...] Match any single char not in []
    ~      Home
    #      this is a comment
    ;      command separator
    &&     execute first one and execute second if first one success (exit
code: 0)
    ||     execute first one and execute second if first one fail (exit code:
!= 0)
    \      Excape char or command continueation indicator
    &      background execution


shell ENV variables:
    control shell behaviors

to dump them:
    "env" command

To get value:
    $variable_name   or ${varible_name}

Useful env variables
sh   / csh        what it is
HOME / HOME       home
MAIL / MAIL       mailbox
PATH / PATH       search path
PS1  / prompt     prompt string
PS2  / prompt2
     / prompt3
IFS  /            internal field separators
     / history    Number of history commands


variables and string quotes

assignment:
    sh:  var=value     csh:  set var=value

get variavle:
    $var or ${var}
    substitution stdout `cmd`
    'string' without substitution
    "string" with substitution

Assignment:

    local variables
        sh: my=test        csh: set my=test

    global variables
        sh: export my      csh: setenv my test


shell I/O:
    stdin  0
    stdout 1
    stderr 2
    user defined: 3~19

redirection:
    change the direction of shess I/O
    creat files
    append to files
    use existing files as input
    merge output streams
    use part of shell command as input

Usage:
    >     open the following file as stdin
    <     open the following file as stdout
    >>    append to the following file
    >&    merge stdout with stderr
    |     pipe stdout into stdin

PIPE:

             pipe   pipe
stdin => cmd1 ==> cmd2 => stdout
              \         \
               ->stderr  ->stderr


build-in shell commands:
    alias / cd / echo / eval / exec / exit
    jobs / kill / fg / bg / set / export
    hash / umask

Useful commands:
    passwd, chsh, chfn, chpass
    pid: ps, top
    directory: ls, mkdir/rmdir
    file: cp/mv/rm
    Email reader: mutt
    News reader: tin
    Connecting: ssh/telnet
    Manual: man, info
    Editor: vim, joe, ee, …etc.
    File Transmittion: ftp, ncftp, lftp, scp, wget, curl
    Compilers: gcc, g++, javac
    Scripting: perl, php, ruby, python
    login/exit/logout/screen

=================================

single user mood => read only
    read only
    mount -u /
    mount -a -t ufs
    swapon -a

how to shut dowm or reboot:
    Turning off the power     <--- don't do that
    shutdown -h               # halt
    shutdown -r               # reboot
    kill -TERM 1              # kill init

    time format (+m):
        hh:mm                 # for Linux
        yymmddhhmm            # for FreeBSD

    power off
        shutdown -p now

=================================
Installing Apps
    Package: (Pre-built)
        Linux: rpm, yum, dpkg
        FreeBSD: pkg_add, pkg_delete, pkg_info, pkg_version
    Source:
        Tarball
        tar zxvf source.tar.gz
        cd source
        ./configure [options]
        make
        make install

Three technologes:
    Packages     Pre-built!
    Ports        /usr/ports/.....
    Tarball      Fetch from internet

pkg_add                   # add a package
    pkg_dd pkg_name
    pkg_add -r pkg_name   # while you don't know the name
pkg_info                  # see some infomation, btw, use it with grep :)
pkg_delete                #delete a package
    pkg_delete pkg_name


How to use ports:
    to find where the application is
    $ whereis application_name
    goto its directory
    $ cd /usr/ports/.../...
    install it! Ports will fetch the tarball and compile the source code
    make && make install clean

portsnap
/etc/portsnap.conf
=> SERVERNAME=portsnap.tw.FreeBSD.org
sudo portsnap fetch extract update        # update your ports

note: use 'rehash' command after install an application  # for tcsh


=================================
X window
    X can be called X, X11, X window
    client-server model
    'Project Athena' @ MIT in 1984


Architecture:
    client: request display service
    server: provide display service
    communicated with X Protocol

Client:
    An application written in X libraries (e.g. Xlib)
    Request service
    Receive events from X server

Server:
    Runs locally and accepys multiple X clients

X protocol:
    local and network based computing look and feel the same

X11 implementation:
    XFree86
    Xorg

window manager:
    A special X Client provides certain look-and-feel window in front of you
    Background desktop theme
    control windows' behaviors
        size:     resize, minimize, maximize
        position: overlap, move

Examples:

     Gnome, KDE, Xfce ...

xdm
    X Display Manager

x11 forwarding