I have recently recieved a question about Lilo in a private email (perhaps caused by my postings to this list). I belive the answer may be of value to others, so I will repost it here. This will also give experts a chance to flame me for spreading misinformation if I have gotten everything wrong :)
Question: > A while back I was having trouble with lilo not recognizing my > drive properly. I overcame this by using the "linear" option in the > lilo.conf. would this do the same thing to overcome the need for > requiring the kernel to reside in the first 1024 cylinders? Answer: I believe the answer is no. Lilo depends on the BIOS to load the kernel (and other files in /boot). If the BIOS cannot acces the location on the drive there is nothing Lilo can do about it, and no linear option can change that. The linear option is used for a slightly different purpose. Lilo needs to know the exact physical location of the files in a format understandable by the BIOS, i.e. as sector/head/cylinder. It obtains this information by recording the linear adress of the files and then quering the kernel for the disk geometry parameters in order to translate the linear location into the sector/head/cylinder format. This may fail occasionally on large disks because the disk parameters obtained from the kernel query may be wrong. The kernel retrives these parameters directly from the device. However, the BIOS may use some implicit translation of sector/head/cylinder adresses in order to overcome the large disk problem. This implicit translation is invisible to the kernel, as the kernel never queries the BIOS. Thus the disk geometry reported by the kernel is incompatible with the disk geometry reported (and used) by the BIOS. A solution to this problem is to use the linear option. This causes Lilo not to query the kernel for the disk parameters. Instead Lilo records the linear physical location of the files, and performs the translation at boot-time by quering the BIOS for the disk parameters during boot. The situation is therefore this: - Some BIOSes cannot acces the upper part of a large disk if the disk reports geometry parameters with more than 1024 sectors. In this case the solution is to partition the disk carefully and place boot files on a partition below the 1024 sectors. - Some BIOSes can handle disks that report a disk geometry above 1024 sectors. These BIOSes uses translation to fool everyone into thinking the disk has less than 1024 sectors. In this case the boot files can be placed anywhere on the disk, but it is necessary to use the linear option to make Lilo aware of this translation. - Some newer large disks perform this implicit translation themselves, and thus reports a geometry to the BIOS and the kernel with less than 1024 sectors. In this case the BIOS can access the entire disk and Lilo operates perfectly with or without the linear option. Drives with this capability are usually referred to as LBA drives (logical block addressing). Conclusion: Always use the linear option. If it works everything is fine. If it doesn't work you must resort to the partitioning trick. Note however, that the linear option should not be used on floppies or together with the compact option (which is only useful on floppies). - Sten Anderson -- TO UNSUBSCRIBE FROM THIS MAILING LIST: e-mail the word "unsubscribe" to [EMAIL PROTECTED] . Trouble? e-mail to [EMAIL PROTECTED] .
