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'''Chpt 5 Study Guide'''
Here is a list of my wiki pages..


== Boot Process ==
Chapter 5 Linux
''System power > CPU looks for BIOS > CPU Runs Bios''


::BIOS checks for new hardware, configure hardware, and looks for boot sector.This is when the BIOS finds the boot loader in
::the boot sector.Boot loader takes over from BIOS. If a multistage loader is available, a secondary loader is searched for.
::Finally, the boot loader finds the kernel, loads it into memory and then executes it. Once the LINUX kernel takes over, it then
::begins to initial devices, mounting root partition and other such tasks.The initial program is also started at this stage.It
::gets a process ID of 1 because it’s the first program run on the system.


Chapter 2 Linux
Chapter 8 Linux
Linux+ Giude to Certificationn, 3rd Ed.


=== Retrieving Information about the boot process ===
Service project for CCNA Security.
: Certain information about the Linux kernel and module log info can be found in the kernel ring buffer.
: This info is displayed during the boot process, but is shown too fast to be read.
: To access this info type the following command..
::   '''#dmesg | less'''
::   '''#dmesg > boot.messages'''
 
=== Locating and Interpreting Boot Messages ===
: Use less and it’s search functions
: Look for hardware type names
: Look for hardware chipset names
Study output from a working system
 
 
== Installing Boot Loaders ==
The master boot record (MBR) contains a partition table and a boot loader (aka boot manager). The boot loader is software which the BIOS reads and executes when the system begins to boot
 
 
=== Two main boot loaders for Linux ===
: '''LILO'''  ''(Linux Loader)''
:: Once the default boot loader.
:: Slowly being overtaken by GRUB.
:: Small, and useful.
 
 
 
: '''GRUB'''  ''(Grand Unified Boot Loader)''
:: Has taken over as default boot loader for many LINUX distributions
:: Offers more configurations than LILO
 
 
==  LILO ==
Can be configured using the /etc/lilo.conf file.
This file is broken into two main sections :
===  Global options : ===
: Boot loader location
: Default stanza
: Boot prompt
: Boot timeout
 
=== Per-Image : ===
: Kept in sections known  as stanzas.
:: Can also be further seperated depending on if they’re for a kernel or OS.
:
Some Per-Image Options include  :
: Linux Boot Image
: Non-Linux Boot Partition
: OS Label
: RAM Disk
 
== GRUB ==
: GRUB has some ‘quirks’
:: Unlike Linux, GRUB numbers drives.
:: Instead of /dev/hda .. It would be /dev/hd0
::: Doesn’t distinguish between PATA, SATA, or SCSI drives.
:: GRUB also numbers partitions on a drive starting with 0, instead of 1
::: So partition 1 on drive 1 would look like this (hd0,0)
::: Floppy devices are referred to as (fd0)
 
: GLOBAL OPTIONS
: Default OS
: Timeout
: Background Graphic
: Per-Image Options
: Title
: GRUB root
: Kernel Specification
 
== Runlevels And Initialization Process ==
Linux relies on runlevels to determine which features are available.
Run levels are labels 0 thru 6. Each one being assigned to a set of services that should be active.
Understanding the purpose of runlevels makes for identifying services that are active easier.
 
 
== Checking runlevel ==
Generally done prior to changing or to check status if something isn’t working
This is done by inspecting the /etc/initab file with the less command or opening it in an editor.
 
== Managing Runlevels ==
Chkconfig
Lists the services and their runlevels.
Ex. Chkconfig –list
ntsysv
Used mainly on Red Hat
Interactive text tool
Use your arrow  keys to select a service.
 
 
== Runlevels ==
: 0 – Transitional, Shuts down the system.
:: Should completely power down the system.
: 1, s, or S – Single user mode.
:: Used for low-level system maintenance impaired by normal system operation.
: 2 – Full muti-user mode with a graphical login.
:: Used on Debian 
: 3 – Full multi-user mode with a console login.
:: Used on Fedora, Mandriva,  Red Hat, and most other distributions.
: 4  – Undefined by default
:: Used for customization
: 5  – Same as runlevel 3 with the addition of having X run with XDM (graphical) login.
: 6 – Used to reboot the system.
:: Also a transitional runlevel.
 
 
== Determining Current Runlevel ==
Once system is up and running runlevel info can be checked by entering :
  # runlevel
N 2
 
The first character is the previous runlevel.
N = system hasn’t changed runlevel since starting
2 =  is the current runlevel
 
== Changing runlevels on a running system ==
This can be done with the init (or telinit), shutdown, halt, reboot, or poweroff commands.
 
 
== Runlevel Services ==
 
Two main ways to affect what programs run as you enter a new runlevel.
 
/etc/inittab
SysV
 
== /etc/inittab ==
Id:runlevels:action:process
Identification code
Consists of a sequence of 1-4 characters to identify its function
Applicable runlevels
List of runlevels for which this entry applies.
Action to be taken
Tells init how to treat the function.
Process to run
Process to run for this entry.
Includes options and arguments
 
== System V (SysV) ==
Controls what startup scrips start or stop services depending on the parameters that are passed.
S
rc passes the start parameter to all scrips that begin with the letter S.
K
rc passes the stop services to all scrips that begin with the letter K.
 
== Vi ==
First  full-screen text editor built for linux.
Used for a emergency recovery situations.
Small and simple
Can fit on a floppy disk.
3 modes of operation
 
 
=== Vi Modes ===
 
 
; '''Command mode'''
: Accepts single letter commands.
: '''i''' and a = enter insert mode
: '''o''' =opens a line below the current one.
 
; '''Ex mode'''
: Used to manipulate and save current flies and run outside programs.
: Type :x from command mode to enter Ex mode.
: '''x''' = the command you want to use.
: Automatically returns to command mode when finished.
: Also referred to as colon commands
 
; '''Insert mode'''
: Used to enter text.
: Most input results in text appearing on the screen.
: Use '''Esc''' key to return to command mode.
 
=== Using Vi ===
Use vi [file name] to launch Vi
: Ex. '''vi lilo.conf'''
:: Have to be in the directory that is holding the file.
 
==== Command mode ====
: The up, down, left, and right keys are used to move the curser.
: '''yy''' and '''dd''' to ''yank (copy)'' text to a buffer.
: '''dd''' also ''deletes'' the lines that are yanked.
: Extentions of the '''y''' and '''d''' commands.
: '''p''' is used to paste the contents of the buffer.
 
==== Ex mode ====
: ''':w''' saves the file.
: ''':q''' quits vi
:: Only works if the changes have been saved or used with '''!'''. (Ex. :q!)
: ''':e''' edits a new file
:: Ex. ''':e /etc/inittab''' loads /etc/inittab for editing.
:: Only works if existing file has been saved or used with an !. (Ex. :e! /etc/inittab)
: ''':![command]''' executes the external command.
:: Ex. :!ls executes the list command.
 
==== Insert mode ====
: In command mode you can use '''R''', '''i''', and '''a''' to enter insert mode.
:: '''R'''  - Enters text replacement.
::: Replace appears in the status line.
:: '''i''' - Enters text insertion
:: '''a''' - Enters text insertion but advances the curser one space.
::: Can be useful at the end of a line
:: '''~''' - Used to change the case of a single word.
:: '''u''' - Undo’s any changes
:: '''o''' - Opens any text.
::: It inserts a new line below the current line while entering insert mode on that line.
:: '''G''' - Goes to a specific line.
:: ''':%s/[oringinal string]/[replacement]'''
::: Replaces all occurrences of one string with another.

Latest revision as of 00:46, 25 April 2012

Here is a list of my wiki pages..

Chapter 5 Linux


Chapter 2 Linux Chapter 8 Linux Linux+ Giude to Certificationn, 3rd Ed.

Service project for CCNA Security.

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