Handling undetected hardware is the second reason for entering data at the boot prompt, and it is the most common reason for doing so during the initial installation. Sometimes, the system has trouble detecting hardware or properly detecting the hardware’s configuration. In those cases, the system needs your input at the boot prompt to properly handle the unknown hardware. A large number of the boot input statements pass parameters to device driver modules. For example, there are about 20 different SCSI host adapter device drivers that accept boot parameters. In most cases, the system detects the SCSI adapter configuration without a problem. But if it doesn’t, booting the system may be impossible. An example of passing kernel parameters to Linux to identify an undetected SCSI adapter device is boot: linux aha152x=0×340,11,7 All hardware parameters begin with a driver name. In this case, it is the aha152x driver for Adaptec 1520 series adapters. The data after the equal sign is the information passed to the driver. In this case, it is the I/O port address, the IRQ, and the SCSI ID. Another boot argument that is directly related to the configuration of device drivers is the reserve argument. reserve defines an area of I/O port address memory that is protected from auto-probing. To determine the configuration of their devices, most device drivers probe those regions of memory that can be legitimately used for their devices. For example, the 3COM EtherLink III Ethernet card is configured to use I/O port address 0×300 by default, but it can be configured to use any of 21 different address settings from 0×200 to 0×3e0. If the 3c509 driver did not find the adapter installed at address 0×300, it could legitimately search all 21 base address regions. Normally, this is not a problem. On occasion, however, auto-probing can return the wrong configuration values. In extreme cases, poorly designed adapters can even hang the system when they are probed. I have never personally seen an adapter hang the system, but some years ago I had an Ethernet card that returned the wrong configuration. In that case, I combined the reserve argument with device driver input, as in this example: boot: linux reserve=0×210,16 ether=10,0×210,eth0 This boot input prevents device drivers from probing the 16 bytes starting at memory address 0×210. The second argument on this line passes parameters to the ether device driver. It tells that driver that the Ethernet adapter uses interrupt 10 and I/O port address 0×210. This specific adapter will be known as device eth0, which is the name of the first Ethernet device. Of course, you’ll want to use the Ethernet adapter every time the system boots. Once you’re sure this boot input fixes the Ethernet problem, store it as a kernel-specific option in the lilo.conf file. For example: image = /boot/vmlinuz-2.2.5-15 label = linux root = /dev/hda3 read-only append = “reserve=0×210,16 ether=10,0×210,eth0″ The ether argument is also used to force the system to locate additional Ethernet adapters. Suppose that the system detects only one Ethernet adapter, and you have two Ethernet devices installed: eth0 and eth1. Use this boot input to force the system to probe for the second device: ether=0,0,eth1 Old Ethernet cards are a major reason for boot prompt input. If you have an old card and experience a problem, read the Ethernet-HOWTO for configuration advice on your specific card. New PCI Ethernet cards do not usually require boot input. Most current Ethernet cards use loadable 23
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