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kernel

下面是簡單介紹 kernel 的各項功能,至於詳細的內容可能就要自己對硬體的了解程度了。

kernel 2.4

  • Code Maturity Level Options
    This option allows configuration of alpha-quality software. It is best to disable this option if the kernel is intended for a stable production system. If you require an experimental feature in the kernel, such as a driver for new hardware, then enable this option but be aware that it “may not meet the normal level of reliability" as tested code.
  • Loadable Module Support
    You will almost certainly want to enable module support. If you will need third-party kernel modules you will also need to enable Set Version Information on All Module Symbols.
  • Processor Type and Features
    This is perhaps the most important option to choose. In the Preparation section we determined our processor type by examining /proc/cpuinfo and we use that information here to select the appropriate processor. Included in this submenu are features such as Low Latency Scheduling which can improve desktop responsiveness, Symmetric Multi-processing Support for machines with multiple CPUs, and High Memory Support for machines with more than 1G of RAM. Laptop users can also benefit from the CPU Frequency Scaling feature.
  • General Setup
    Choices for PCI, ISA, PCMCIA and other architectural support such as Advanced Power Management are found here.
  • Memory Technology Devices
    MTD devices include Compact Flash devices. Some digital cameras will require this support.
  • Block Devices
    The Block Device section contains options for floppy and hard drives, including parallel port devices, tape drives and RAID controllers. Important options include loopback device support, which allows mounting on disk images, and initrd support, which is needed to preload drivers necessary to boot the system.
  • Multi-Device support (RAID and LVM)
    Important for servers, these options include RAID support for combining multiple disks. Note that this option is not needed for certain hardware RAID that function below the operating system level. LVM is a useful subsystem that allows, among other things, dynamic resizing of filesystems.
  • ATA/IDE/MFM/RLL support.
    This section includes options for IDE/ATAPI chipsets, including performance tweaks such as DMA. Most systems will need this support.
  • Cryptography Support (CryptoAPI)
    Useful options include Loopback Crypto Support, which allows encrypted filesystem images to be mounted. Even with full access to the PC, loopback encryption can help safeguard data.
  • Networking Options
    Many choices are available for networking. TCP/IP, IP tunneling, packet filtering, IPv4 and IPv6, routing support and network QoS are among the most useful. If your kernel is intended for a dedicated firewall or router device, then the options here can significantly improve performance. Read the online and kernel documentation.
  • SCSI Support
    SCSI support is needed for not only true SCSI devices, but also for IDE CDR/W drives in SCSI emulation mode. If your root filesystem is mounted on a SCSI disk, then you must build support directly into the kernel and not as a module.
  • Character Devices
    Dozens of options are available here, including support for many serial and parallel devices, hardware sensors (for system monitors), mice, joysticks and DRM. Many of the options can be safely disabled without problem.
  • File Systems
    It is a good idea to build support for your root filesystem directly into the kernel. Though the initrd utilities can get around the chicken-and-egg boot problem, it is generally safer and easier to just build the fs modules directly. Many options can also be safely disabled if you have no use for the feature.

kernel 2.6

  • Code Maturity Level Options
    This option allows configuration of alpha-quality software or obsoleted drivers. It is best to disable this option if the kernel is intended for a stable production system. If you require an experimental feature in the kernel, such as a driver for new hardware, then enable this option but be aware that it “may not meet the normal level of reliability" as more rigorously tested code.
  • General Setup
    This section contains options for sysctl support, a feature allowing run-time configuration of the kernel. A new feature, kernel .config support, allows the complete kernel configuration to be viewed during run-time. This addresses many requests to be able to see what features were compiled into the kernel.
  • Processor Type and Features
    This is perhaps the most important configuration choice. In the Preparation section we determined our processor type by examining /proc/cpuinfo and we use that information here to select the appropriate processor. Included in this submenu are features such as Preemptible Kernel which can improve desktop responsiveness, Symmetric Multi-processing Support for machines with multiple CPUs, and High Memory Support for machines with more than 1G of RAM.
  • Power Management Options
    Found here are options for ACPI and CPU Frequency Scaling which can dramatically improve laptop power usage. Read the Documentation/power file for more information.
  • Bus Options ( PCI, PCMCIA, EISA, MCA, ISA)
    Here are found options for all system bus devices. On modern machines the ISA and MCA support can often be disabled.
  • Executable File Formats
    Interesting features here include the kernel support for miscellaneous binaries, which can allow seamless operation of non-Linux binaries with a little userland help.
  • Device Drivers
    All the device-driver configuration options that were previously scattered throughout the 2.4.x menus are now neatly organized under this option. Features such as SCSI support, graphic card optimizations, sound, USB and other hardware are configured here.
  • File Systems
    Found here are options for filesystems which are supported by the kernel, such as EXT2 and ReiserFS. It is best to build support for the root filesystems directly into the kernel rather than as a module.
  • Security Options
    Interesting options here include support for NSA Security Enhanced Linux and other, somewhat experimental, features to increase security.

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