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Topic 101: Hardware & Architecture
Objective 1.101.1: Configure Fundamental BIOS Settings:
The /proc/ file system
To fulfill this objective, candidates must be able to verify IRQ, DMA and I/O settings on the system. Stud
ents also need to be able to change these settings. To perform these tasks, you first must understand the
/proc/ file system.

The /proc/ file system
The /proc/ file system is created at each boot time. The files are mirrored (i.e., copied) from existing system
settings and placed into the /proc/ directory.It reflects the system's current configuration and contains
files and directories that the system uses to configure how it functions. Essential files and directories
include those in Table 1:
File or Directory
Description
/proc/ioports
Provides detailed information concerning the hardware resources that the sys-
tem is using. If a device is recognized, it will receive an I/O address. An example
of an I/O address is: 03c0-03df. If the device does not have an I/O address, it
has not been recognized.
/proc/interrupts
Describes the particular interrupt used by a device. Devices can share inter-
rupts. If you are using a system with two CPUs, you will receive a listing of
interrupts for each CPU.
/proc/dma
Describes channel that ISA and other devices register for Direct Memory
Access (DMA).
/proc/pci
Contains information about operational PCI devices.
/proc/partitions
Provides detailed information about operational partitions.
/proc/cpuinfo
Statistics about the CPU(s) currently operating,
/proc/uptime
Shows how long the system has stayed operational. The first number shows
uptime in seconds. The second number shows how many seconds the running
system has been idle.
/proc/sys/net/ipv4/
Contains various files that allow you to view, enable or disable network re-
sources. For example, changing the value of /proc/sys/net/ipv4/icmp_echo_ig-
nore_all from 0 to 1 will prohibit the system from sending or receiving all ICMP
packets, including those used by the ping command.
Table 1 Mega Guide

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To disable devices, you can take the following steps:
Edit files in the /proc filesystem. Understand, however, that if you edit these files, the settings you
generate will remain valid only until the next boot. You can, of course, create scripts to automati-
cally alter files in the /proc/ directory.
Change jumper settings on the devices you want to attach to the system.
As you add systems, verify that that there are no conflicting devices. For the exam, make sure that you
understand the format of the files given in the above table. Also, make sure that you check on the /proc/io-
ports and /proc/interrupts files. It is possible for devices to share the same interrupt. However, they should
not share the same I/O address.

Objective 1.101.1: Configure Fundamental BIOS Settings:
Configuring Ports and Creating Headless Linux systems
Many times, an integrated peripheral can be enabled or disabled by going in to the BIOS settings and
configuring the settings for each port. Ports for integrated peripherals can include:
Serial ports: Often used to connect a null modem cable, which can be used to transfer data
between systems, connect to a modem, or connect to a keyboard.
Parallel ports (IEEE 1284): Used in various situations, but most often to connect to a printing
device. Although parallel ports are less used in production systems, it is important to understand
that you can configure speeds for these ports. Available speeds include:
Compatibility mode: The original specification, for simple 8-bit transfer.
Nibble mode: Designed for printers, allows two-way communication at 4-bits at a time, but only
one way at a time. In this way, transmission is unidirectional.
Byte mode: A legacy mode that allows parallel ports to receive data more quickly. Disables the
drivers that would place outgoing data onto the line.
Enhanced Parallel Port (EPP): Half-duplex communication, for non-printing devices.
Extended Capability Port (ECP): Enables half-duplex, bi-directional communication that allows
compression. The fastest standard (2.5 Mbps).
SCSI devices: Production Linux systems often use SCSI devices. The order in which the SCSI card
is detected can determine the difference between a system that boots into Linux, and one that
simply hangs.
Serial ATA (SATA) devices: Serial devices include current hard drives.
IDE devices: You can configure the order in which floppy, hard, CD and DVD drives are config-
ured. Although floppy disks are very rare today, many servers still have them, and they are neces-
sary for the initial booting of systems when performing updates. Also, IDE drives are in many
older systems, which many beginners in Linux may be using. After all, many older systems that
are just lying around can run Linux and are very useful in a home lab setting.
USB ports: USB devices are not considered integrated devices by LPI. Nevertheless, you should
understand that you can enable or disable the USB devices through BIOS.Headless Linux systems
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There will also be times that you will have to use a headless Linux system. A headless system is a com-
puter that does not have a keyboard or monitor attached. Sometimes, these headless systems are servers
connected to a device that allows the server administrator or programmer to switch from one computer
to the next. At other times, they are embedded Linux systems, where the operating system works behind
the scenes, and there is no command-line or GUI interface for the user.

BIOS systems in headless computers require special configuration. For example, many x386 systems will
not boot if a keyboard is not attached. To solve this problem, enter into the system's BIOS and configure it
to ignore a missing keyboard.

You access a system's BIOS settings at boot during the boot time. During the boot time, the key you press
to enter the system's BIOS configuration program differs from computer to computer. Sometimes, the F10
key will allow you to access the BIOS settings. With other systems, the DELETE key must be pressed. The
system Power On Self Test (POST) screen will inform you.

Once you have accessed the BIOS configuration program, find the screen that allows the system to skip
the keyboard check. Some systems will also cause problems if a graphics card is not installed. Similarly, find
the settings that allow you to bypass checking for a card.

Troubleshooting headless systems
Below are some common issues when configuring headless system:
Keyboard and video will not work, even when they are attached: Make sure that you have
activated the serial port and that the mappings are correct in the /etc/inittab file.
The system won't boot to a GRUB or LILO prompt: Many times, a system will not proceed if it
detects that a keyboard is missing. If your system will not boot, make sure that you have disabled
either the keyboard port, or that you have disabled the portion of the POST that checks for the
keyboard. The option to look for is often called Halt on, or Keyboard halt.

Note: It is possible to use a null modem cable to test ports to make sure that they are usable .

Checking serial ports
When checking serial ports, use the dmesg command. You will be able to determine the ports that
are running:

$ dmesg | grep ttyS

ttyS0 at 0x03f8 (irq = 4) is a 16550A

Communication programs
When communicating with the ports, you can use various applications, including:

minicom: The standard terminal.

gtkterm: A GUI-based alternative, based on Hyperterminal.
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If you find that you can't log in as root on the terminal, the /etc/securetty file may not have been updated.
Any terminal listed in this file will allow root logins. If the terminal is not listed, root cannot log in. To up-
date the file, simply place the terminal name in it. You must be root. For example, if you wish to allow ttyS0
to allow root logins, you simply add the following line:


ttyS0

You may not wish to have the terminal to boot into X, assuming that the headless system is being used as
a server. To have it boot into a standard terminal, enter the following in /etc/inittab:


id:3:initdefault:

Finally, it is possible to allow the serial