Chapter 9 Flashcards
The – initializes itself and begins sending out signals to control other parts of the computer
cpu
The – performs a power-on self test (post)
BIOS
– checks memory and other hardware, such as detecting the type of storage devices that are attached to the system
BIOS
The – sends a signal to the SCSI controller card (if one is installed), telling it to initialize itself.
BIOS
In nearly all cases, however, the – actually loads a small program called a –.
BIOS
Bootloader
The two bootloaders that are commonly used on Linux are – and –.
GRUB (Grand Unified Boot Loader)
LILO ( Linux Loader)
(Bootloaders) – is a more advanced program and is the default on most systems
GRUB
A – lets you control which of many operating systems is started each time you turn on your computer.
Boot loader
The boot loader, can be stored on the –
Master Boot Record (MBR)
In Linux, the kernel is just a regular file, normally stored in the –
/boot subdirectory.
The kernel is normally a file named – in the –
vmlinuz in the /boot directory
After booting a version of Linux, you can use the – command to display information about the kernel to see exactly which version you are using.
uname
This command displays the full number of the current kernel:
$ uname -a
The following command displays a timestamp of the kernel, showing when it was compiled.
$ uname -v
The – initializes the PCI bus, sets up network protocols, and initializes device drivers, so it can communicate with device drivers
kernel
You can execute the – command to view the messages stored by the kernel during the boot process.
dmesg
the – command displays the contents of the – – – , an area where messages from the kernel are stored.
dmesg
Kernel ring buffer
(Note) dmesg
if the memory space fills up, the oldest messages are discarded.
|
(Note)
If you do not start dmesg command right after you start the computer, the dmesg command may display only messages that the kernel generated after the hardware was initialized. In that case, you can view the contents of the file – with less or a text editor.
/var/log/dmesg
By using the boot parameter –, you can start Linux in a special single-user maintenance mode.
single
linux single
– are codes that instruct Linux how to operate or how to access parts of the computer systems hardware.
boot parameters
The – command shows you how much memory the kernel is aware of.
free
You can use the – boot parameter to tell Linux how much memory you really have. (Note that if you tell the Kernel that you have more memory than you really have, it will eventually crash trying to access nonexistent memory.
mem=
Example
linux mem=512m
The standard configuration file for Lilo is –
/etc/lilo.conf
To use – after installing Linux, you create a configuration file describing the operating systems that you want – to be able to use.
LILO
Because Lilo is designed for booting Linux kernels, each version of Linux is referred to as a –
Boot Image
This line tell the lilo command where to stroe the boot loader.
boot = /dev/h da:
Example
boot = /dev/hda2
This line determines how long LILO waits until it start an operating system.
delay = 10:
In this case, after 10 seconds llilo starts the default operating system.
(Note)
other = /dev/hda3: this line defines non-Linux operating system. If a user selects this item, LILO passes control to the boot record of the third partition on the first IDE hard disk (dev/hda3).
|
The configuration file for GRUB (the default boot manager in Red Hat Linux is
/boot/grub/grub.conf
The – file includes global configuration details as well as a configuration for one or more operating systems.
grub.conf
This line defines which of the defined operating systems are started automatically if the user does not make a selection
default=0
This line defines how long Grub waits for user input before starting the default operating system.
timeout=10:
Grub will wait 10 seconds in this case.
This line defines a graphic image that GRUB displays at start-up.
splashimage=.
The – configuration file is used to define the menu options (and splash screen) presented when you start your computer.
grub.conf
the – – is a master control program that starts many other programs such as the program that provides a login prompt.
init program
(Run Levels)
0
(Name) Halt
Shuts down all services when the system will not be restarted.
(Run Levels)
1
(name) Single-user mode
Used for system maintenance. Does not require logging in with a user name and password- operates as root. Does not provide networking capabilities.
(Run Levels)
2
(Name) Multiuser networking enabled
Rarely used except for system maintenance or testing.
(Run Levels)
3
(name) Regular multiuser networking mode
Standard multiuser text-mode operation; non-graphical systems (such as network servers) use this mode for normal operation.
(Run Levels)
4
not used
(Run Levels)
5
(Name) Graphical Login
Identical to run level 3 except a graphical login is used.
(Run Levels)
6
(Name) Reboot
Shuts down all services so the system can be restarted.
The – line defines a special file that Grub loads first to help get the kernel loaded
initrd
The – file extension refers to a very simple graphical file format.
.xpm
by using the – or – command (they are equivalent) you can tell the init program to change to a different run level.
init or telinit
(Example)
# telinit 6
A – tracks each disk operation to be certain that it is either completed or not done at all.
Journaling file system
An orderly or methodical shutdown of linux is also called a –
graceful shutdown
Lilo and Grub are each configured using text configuration files stored in the /boot directory
|
Scripts start or stop a services based on the settin in a run level directory. Symbolic links begin with either a – to stop a service or – to start a service in that run level.
k to stop
S to start
– Configures which services are started by default when you boot Linux.
chkconfig
The following example restarts the printing service.
service lpd restart
