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'''Chpt 5 Study Guide'''


== Boot Process *(pg. 240) == 
''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.
=== Retrieving Information about the boot process *(pg. 239)===
: 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 (pg. 239) ===
: 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 (pg. 226) ==
:: 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)'' (pg. 228)====
:: ''Once the default boot loader.''
:: ''Slowly being overtaken by GRUB.''
:: ''Small, and useful.''
:: ''Can be configured using the '''/etc/lilo.conf''' file.''
:: Which 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 separated depending on if they’re for a kernel or OS.''
::: Linux Boot Image
::: Non-Linux Boot Partition
::: OS Label
::: RAM Disk
==== '''GRUB'''  ''(Grand Unified Boot Loader)'' (pg. 233) ====
:: ''Has taken over as default boot loader for many LINUX distributions''
:: ''Offers more configurations than LILO''
::: 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 (pg. 241) ==
: 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 (pg. 245) ===
: '''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. space bar to toggle the service on or off.
::      Use the '''--level''' option to select other or multiple runlevels.
=== Runlevels (pg. 242) ===
: '''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.
::''shutdown [option] [time] “[Message]” ''     
::: ex. '''shutdown –r +15''' “System going down for maintenance.” 
:Options 
:: '''-h''' ...Halt or power off the computer. (runlevel 0) 
:: '''-r''' ...Reboots the system. (runlevel 6) 
:: '''-c''' ...Cancels a scheduled shutdown.  Time  hh:mm
:::'' Tells the computer when to run the shutdown command in a 24 hour format.'' 
:: '''+ t''' ...t = time to shutdown in minutes. 
:: '''Message''' ...Adds a message at the end of the command
== Runlevel Services (pg.243) ==
=== Two main ways to affect what programs run as you enter a new runlevel.===
:: '''/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
:: '''SysV''' (pg.244)
::: 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 (pg. 250) ==
: ''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'''
==== 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.
'''NOTE''' : ''all page numbers reference the CompTIA Linux+ Complete Study Guide  by Roderick W. Smith ISBN 978-0-470-88845-2''

Revision as of 00:44, 25 April 2012

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