Certification Objective 2.01-Hardware Compatibility


Now it's time to explore the hardware that RHEL can handle. While some manufacturers now include their own Linux hardware drivers, most Linux hardware support comes from third parties. Fortunately, a vast community of Linux users are hard at work, producing Linux drivers and more, even distributing them freely on the Internet. If a certain piece of hardware is popular, you can be certain that Linux support for that hardware will pop up somewhere on the Internet and will be incorporated into various Linux distributions, including RHEL.

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Inside the Exam

Focus During Installation

Both the RHCE and RHCT exams include an Installation and Configuration section. You'll have to do more than just install Linux. You'll follow a series of instructions, configure custom partitions, and configure certain services.

Time limits are severe on these exams. Install and configure as much as you can when you install RHEL on your computer. Although you can configure and install almost anything after Linux is installed, that can take more time than you have.

On the other hand, don't install everything. It takes time to install gigabytes of software over a network. If you're spending time installing software that you don't need, that's time you can't get back during the exam.

As you read this chapter, learn every part of the installation process. Know what you need to install. For example, if you see a requirement to set up Apache and Samba servers, you'll want to install the Web Server and Windows File Server package groups when you install RHEL.

Studying for the Installation and Configuration Section

You can use one of the "rebuilds" of RHEL 5 or even Fedora Core 6 to study for the Installation portion of the RHCE and RHCT exams. The steps required are essentially identical to those for RHEL 5. To assure you that the steps are the same, consult "Installing Red Hat Enterprise Linux 5" in the Online Learning Center (http://highered.mhhe.com/sites/0072264543), which provides a pictorial-only guide to the RHEL 5 installation process.

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Be careful when purchasing a new computer to use with Linux. Though Linux has come a long way the last few years, and you should have little problem installing it on most modern PCs, you shouldn't assume Linux will install or run flawlessly on any PC, especially if the PC in question is a state-of-the-art laptop computer (though several major laptop manufacturers seem determined to maintain good relationships with the Linux community). Laptops are often designed with proprietary configurations that work with Linux only after some reverse-engineering. For example, when I installed Red Hat Enterprise Linux on a new widescreen laptop, I could install only in text mode.

Other types of hardware, such as "winmodems" and "winprinters," are designed to use Microsoft Windows driver libraries. Integrated hardware (such as video chips that share system RAM) and parallel port devices can also be problematic. While Linux drivers exist for many of these devices, do your research.

Linux runs very well on lower-end computers. This is one of Linux's strong points over other operating systems, especially Microsoft Windows Vista. Linux runs fine on 64MB of RAM, although more is always better, especially if you want to run any graphical applications. RHEL 5 does require a minimum of 192MB of memory to start the graphical installer. However, the latest versions of Linux do have limits; modern distributions don't run on anything less than a Pentium-class system.

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Exam Watch

While it is important that you know how to select and configure hardware components to get to a smoothly running Linux computer, the RHCE and RHCT exams are not hardware exams.

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Linux Hardware Documentation

Many resources are available to help you select the best hardware for Linux. Thousands of Linux gurus are available online via mailing lists, IRC rooms, and newsgroups. Perhaps the best places to look are the Linux Documentation Project (LDP) or the Red Hat Hardware Compatibility List (HCL). The LDP is a global effort to produce reliable documentation for all aspects of the Linux operating system, including hardware compatibility.

Linux Hardware HOWTO

The Linux Hardware HOWTO is a document listing most of the hardware components supported by Linux. It's updated irregularly with added hardware support, so it is a relatively up-to-date source of information, available at www.tldp.org.

The Red Hat Hardware Compatibility List

The Red Hat HCL is different from the one you'll find in the Linux Hardware HOWTO. It specifies name brand hardware that has been tested with various versions of RHEL. If you've purchased RHEL, Red Hat will provide some level of installation support for any certified or compatible hardware. Some hardware that has been tested by Red Hat has specifically been found not to work with Red Hat Linux or RHEL and is therefore not supported. Red Hat doesn't have the resources to test more than a limited range of hardware; most PCs and servers built today work well with RHEL. For that information, refer to the aforementioned Linux Hardware HOWTO.

Plug and Play and the Hardware Abstraction Layer

Plug and play (PnP) refers to the ability of an operating system to allocate hardware ports or addresses automatically to specific devices such as hard drives, sound cards, or modems. Linux's ability to work with PnP devices is finally up to speed, courtesy of the Linux implementation of the Hardware Abstraction Layer (HAL). Conceptually different from the Microsoft version, HAL provides a constant list of detected components. Some distributions can now automatically detect and mount the smart cards associated with digital cameras and fingerprint readers.

If you want to see the full list of detected hardware, run the lshal command. It's a long list; you may need to pipe the output to a pager with a command like:

 # lshal | less 

which allows you to scroll through the output.

Channel Conflicts

In rare cases, the Linux HAL subsystem may have problems with the newest computer devices or some very old ones. If you're having problems with the newest computer equipment, various Web sites are dedicated to offering help. For example, www.linmodems.org can help you configure many so-called "winmodems," and www.linux-usb.org can help you configure the latest USB equipment on Linux.

Many hardware conflicts with relatively old equipment are fairly simple to eliminate. There are three possible areas of conflict:

  • A physical hardware jumper is conflicting with another card.

  • Your ISA cards are not properly configured.

  • You are out of IRQs or other resources to add to your new device.

You can use the /proc files to check the currently used IRQ ports, I/O addresses, and DMA channels. For example, to check the occupied IRQs, the following command lists the devices that are loaded by the kernel:

 # cat /proc/interrupts 

If there is a conflict, the device is not loaded. You can quickly scan over the left side to see what interrupts are available. To get a list of used I/O addresses and DMA channels, issue the following commands:

 # cat /proc/ioports # cat /proc/dma 

The kernel included with RHEL 5 and above should keep HAL configuration problems to a minimum. When problems arise, two or more devices are probably trying to use the same IRQ, I/O, and/or DMA. In that case, one or both devices may not be loaded. It may take a little detective work to identify the troubled hardware; conflicts may prevent it from being listed in one of the associated /proc directory files. Then select one of the devices, and change its IRQ, I/O, and/or DMA to a free location.

This is usually a two-step process: first, change the settings on the card itself through physical jumpers or a diagnostic disk, as described in the next section. If Linux doesn't detect your changes, use the appropriate configuration tool, such as system-config-keyboard, ifconfig, modprobe, or system-config-network, to change the settings on your device.

Generally, Linux should not have problems with PCI cards, USB devices, or even many IEEE 1394 (also known as FireWire or iLink) systems. Linux should recognize them and set them up with appropriate IRQ ports, I/O addresses, and DMA channels. If you cannot see what your PCI cards are set to, type cat /proc/pci. If a PCI card that you're concerned about does not show up here, you may be out of IRQs. If you run out of IRQs, you may want to look into alternatives such as IEEE 1394 or USB devices.

Some Linux distributions may not detect multiple CPUs, or the different CPUs associated with dual-core systems (unless you've installed the right kernel). To know what CPUs are detected, check /proc/cpuinfo.

ACPI and APM

Closely related to HAL are the computer power management standards, known as Advanced Configuration and Power Interface (ACPI) and Advanced Power Management (APM). Both are efforts to manage PC power consumption. As such, they are important tools to extend the lifetime of battery-operated devices such as laptop computers.

Microsoft has driven developments in both areas toward computers that can be easily suspended and reactivated from a minimum power state. On Linux systems, some customization may be required, especially for laptops. For this purpose, the experience of others as documented on sites such as www.tuxmobil.org are most valuable. The experiences of others, as documented on that Web site, helped me customize the functionality of multimedia buttons on my dual-core laptop system.

If you have problems with an ACPI computer, you can deactivate ACPI support with the acpi=off command to the kernel during the RHEL boot or installation process.



RHCE Red Hat Certified Engineer Linux Study Guide (Exam RH302)
Linux Patch Management: Keeping Linux Systems Up To Date
ISBN: 0132366754
EAN: 2147483647
Year: 2004
Pages: 227
Authors: Michael Jang

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