Important Kernel Configuration Features

The xconfig, menuconfig, and gconfig tools provide excellent context-sensitive help for each entry. To the right of each entry is a Help button. Click it to display a detailed explanation of what that feature does and why you would include it either directly or as a module, or even exclude it. When you are in doubt about a feature, always use the Help button to learn exactly what it does and why you would want to use it. Many of the key features are described here. Corresponding entries for the 2.6 kernel are listed in parenthesis.

• Loadable Module Support   In most cases, you should make sure your kernel can load modules. Click the Loadable Module Support button to display a listing of several module management options. Make sure Enable Loadable Module Support is marked Yes. This feature allows your kernel to load modules as they are needed. Kernel Module Loader should also be set to Yes, because this allows your daemons, such as your Web server, to load any modules they may need.

• Processor Type And Features   The Processor Type And Features window enables you to set up support for your particular system. Here, you select the type of processor you have (486, 586, 686, Pentium III, Pentium IV, and so forth), as well as the amount of maximum memory your system supports (up to 64GB with the 2.4 kernel).

• General Setup   The General Setup window enables you to select general features, such as networking, PCI BIOS support, and power management, as well as support for ELF and a.out binaries. Also supported is sysctl for dynamically changing kernel parameters specified in the /proc files. You can use redhat-config-proc (the Kernel Tuning tool in the System Tools menu) to make these dynamic changes to the kernel. In the additional device driver support menu, you can enable specialized features like Crypto IP Encapsulation (CIPE) and accelerated SSL.

• Block Devices (Device Drivers)   The Block Devices window lists entries that enable support for your IDE, floppy drive, and parallel port devices. Special features, such as RAM disk support and the loopback device for mounting CD-ROM image files, are also there.

• Multi-Device Support (RAID and LVM) (Device Drivers)   The Multi-Device Support window lists entries that enable the use of RAID devices. You can choose the level of RAID support you want. Here you can also enable Logical Volume Management support (LVM), which lets you combine partitions into logical volumes that can be managed dynamically.

• Networking Options (Filesystems and Device Drivers)   The Networking Options window lists an extensive set of networking capabilities. The TCP/IP Networking entry must be set to enable any kind of Internet networking. Here, you can specify features that enable your system to operate as a gateway, firewall, or router. Network Aliasing enables support for IP aliases. Support also exists for other kinds of networks, including AppleTalk and IPX. AppleTalk must be enabled if you want to use NetTalk to connect to a Macintosh system on your network (Filesystems).

• ATA/IDE/MFM/RLL Support (Device Drivers)   In the ATA/IDE/MFM/RLL Support window, you can click the "IDE, ATA, and ATAPI Block Device" button to open a window where you can select support for IDE ATA hard drives and ATAPI CD-ROMs.

• SCSI Support (Device Drivers)   If you have any SCSI devices on your system, make sure the entries in the SCSI Support window are set to Yes. You enable support for SCSI disks, tape drives, and CD-ROMs here. The SCSI Low-Level Drivers window displays an extensive list of SCSI devices currently supported by Linux. Be sure the ones you have are selected.

• Network Device Support (Device Drivers/Networking Support)   The Network Device Support window lists several general features for network device support. There are entries here for windows that list support for particular types of network devices, including Ethernet (10 or 100MB) devices, token ring devices, WAN interfaces, and AppleTalk devices. Many of these devices are created as modules you can load as needed. You can elect to rebuild your kernel with support for any of these devices built directly into the kernel.

• Multimedia Devices (Device Drivers)   Multimedia devices provide support for various multimedia cards as well as Video4Linux.

• File Systems (Filesystems)   The File Systems window lists the different types of file systems Linux can support. These include Windows file systems such as DOS, VFAT (Windows 95/98), and NTFS, as well as CD-ROM file systems such as ISO and UDF. Network file systems such as NFS, SMB (Samba), and NCP (NetWare) are included, as well as miscellaneous file systems such as HFS (Macintosh).

• Character Devices (Device Drivers)   The Character Devices window lists features for devices such as your keyboard, mouse, and serial ports. Support exists for both serial and bus mice.

• Sound (Device Drivers)   For the 2.4 kernel, the Sound window lists different sound cards supported by the kernel. Select the one on your system. For older systems, you may have to provide the IRQ, DMA, and Base I/O your sound card uses. These are compiled as separate modules, some of which you could elect to include directly in the kernel if you want. For the 2.6 kernel, you can select the Advanced Linux Sound Architecture sound support, expanding it to the drivers for particular sound devices (the Open Sound System is also included, though deprecated).

• Bluetooth Devices (Device Drivers/Networking)   Support is here for Bluetooth-enabled peripherals, listing drivers for USB, serial, and PC card interfaces.

• Kernel Hacking (Kernel hacking)   The Kernel Hacking window lists features of interest to developers who work at the kernel level and need to modify the kernel code. You can have the kernel include debugging information, and also provide some measure of control during crashes.

Once you set your options, save your configuration. The Save And Exit option overwrites your .config configuration file. The Store To Configuration File option lets you save your configuration to a particular file.

Tip

Red Hat Linux incorporates support for the Native POSIX Thread Library (NPTL), an updated version of Linux POSIX threads, providing for more efficient use of high-end processors. Though this feature was designed to be backward compatible, some older modules may prove incompatible and may need to be recompiled with the new kernel.