prep revision 1.3.2.2
1 1.1 cgd First and foremost, before beginning the installation process, MAKE 2 1.1 cgd SURE YOU HAVE A RELIABLE BACKUP of any data on your hard disk that you 3 1.3.2.1 perry wish to keep. Mistakes in partitioning your hard disk may lead 4 1.3.2.1 perry to data loss. 5 1.1 cgd 6 1.3.2.1 perry Before you begin, you should be aware of the geometry issues that may 7 1.3.2.1 perry arise in relation to your hard disk. First of all, you should know 8 1.3.2.1 perry about sector size. You can count on this to be 512 bytes; other sizes 9 1.3.2.1 perry are rare (and currently not supported). Of particular interest are 10 1.3.2.1 perry the number of sectors per track, the number of tracks per cylinder 11 1.3.2.1 perry (also known as the number of heads), and the number of cylinders. 12 1.3.2.1 perry Together they describe the disk geometry. 13 1.3.2.1 perry 14 1.3.2.1 perry The BIOS has a limit of 1024 cylinders and 63 sectors per track for 15 1.3.2.1 perry doing BIOS I/O. This is because of the old programming interface 16 1.3.2.1 perry to the BIOS that restricts these values. Most of the big disks 17 1.3.2.1 perry currently being used have more than 1024 real cylinders. Some have 18 1.3.2.1 perry more than 63 sectors per track. Therefore, the BIOS can be instructed 19 1.3.2.1 perry to use a fake geometry that accesses most of the disk and the fake 20 1.3.2.1 perry geometry has less than or equal to 1024 cylinders and less than or 21 1.3.2.1 perry equal to 63 sectors. This is possible because the disks can be 22 1.3.2.1 perry addressed in a way that is not restricted to these values, and the 23 1.3.2.1 perry BIOS can internally perform a translation. This can be activated 24 1.3.2.1 perry in most modern BIOSes by using 'Large' or 'LBA' mode for the disk. 25 1.3.2.1 perry 26 1.3.2.1 perry NetBSD does not have the mentioned limitations with regard to the 27 1.3.2.1 perry geometry. However, since the BIOS has to be used during startup, 28 1.3.2.1 perry it is important to know about the geometry the BIOS uses. The 29 1.3.2.1 perry NetBSD kernel should be on a part of the disk where it can be 30 1.3.2.1 perry loaded using the BIOS, within the limitations of the BIOS 31 1.3.2.1 perry geometry. The install program will check this for you, and 32 1.3.2.1 perry will give you a chance to correct this if this is not the case. 33 1.3.2.1 perry 34 1.3.2.2 perry If you have not yet installed any other systems on the hard disk 35 1.3.2.1 perry that you plan to install NetBSD on, or if you plan to use the 36 1.3.2.1 perry disk entirely for NetBSD, you may wish to check your BIOS 37 1.3.2.1 perry settings for the 'Large' or 'LBA' modes, and activate 38 1.3.2.2 perry them for the hard disk in question. While they are not needed 39 1.3.2.1 perry by NetBSD as such, doing so will remove the limitations mentioned 40 1.3.2.1 perry above, and will avoid hassle should you wish to share the disk with 41 1.3.2.1 perry other systems. Do NOT change these settings if you already have 42 1.3.2.1 perry data on the disk that you want to preserve! 43 1.3.2.1 perry 44 1.3.2.1 perry In any case, it is wise to check your the BIOS settings for the 45 1.3.2.2 perry hard disk geometry before beginning the installation, and write 46 1.3.2.1 perry them down. While this should usually not be needed, it enables 47 1.3.2.1 perry you to verify that the install program determines these values 48 1.3.2.1 perry correctly. 49 1.3.2.1 perry 50 1.3.2.1 perry The geometry that the BIOS uses will be referred to as the "BIOS 51 1.3.2.1 perry geometry", the geometry that NetBSD uses is the "real geometry". 52 1.3.2.1 perry 53 1.3.2.1 perry Sysinst will try to discover both the real geometry and BIOS 54 1.3.2.1 perry geometry. If a Master Boot Record (MBR) has been written to 55 1.3.2.1 perry your disk by DOS, Windows 95, NT, or another system, sysinst should 56 1.3.2.1 perry have no trouble find the BIOS geometry. If the disk has not had a MBR 57 1.3.2.1 perry written to it, it may be much more difficult to get the BIOS geometry. 58 1.3.2.1 perry 59 1.3.2.1 perry It is *important* that sysinst know the proper BIOS geometry to be able 60 1.3.2.1 perry to get NetBSD to boot, regardless of where on your disk you put it. 61 1.3.2.1 perry It is less of a concern if the disk is going to be used entirely for 62 1.3.2.1 perry NetBSD. If you intend to have several OSes on your disk, this becomes 63 1.3.2.1 perry a much larger issue. 64 1.3.2.1 perry 65 1.3.2.1 perry Another issue with geometry is with SCSI disks. The geometry reported 66 1.3.2.1 perry by the disk often does not address all addressable sectors on the disk. 67 1.3.2.1 perry sysinst will assist you if you want to choose a fake geometry for 68 1.3.2.1 perry NetBSD to use so it can get access to more sectors. This is not 69 1.3.2.1 perry the same as the BIOS fake geometry. 70
Indexes created Sat Nov 08 12:09:53 GMT 2025