From b0db2901b9e47b793cf5b30893e3d8d063f1ccea Mon Sep 17 00:00:00 2001 From: Joerg Wunsch Date: Sun, 7 Sep 1997 14:04:39 +0000 Subject: [PATCH] Add a chapter about ``dangerously dedicated'' disks, their pro's and con's. --- FAQ/FAQ.sgml | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 89 insertions(+), 3 deletions(-) diff --git a/FAQ/FAQ.sgml b/FAQ/FAQ.sgml index f290aa6441..0dd6a3e675 100644 --- a/FAQ/FAQ.sgml +++ b/FAQ/FAQ.sgml @@ -1,12 +1,12 @@ - +
Frequently Asked Questions for FreeBSD 2.X <author>Maintainer: Peter da Silva <tt><htmlurl url='mailto:peter@taronga.com' name='<peter@taronga.com>'></tt> -<date>$Date: 1997-09-07 12:17:46 $</date> +<date>$Date: 1997-09-07 14:04:39 $</date> <abstract> This is the FAQ for FreeBSD systems version 2.X All entries are @@ -784,7 +784,7 @@ make release BUILDNAME=3.0-MY-SNAP CHROOTDIR=/some/big/filesystem/release reasonably careful, a 20 megabyte boot partition should be plenty. <sect1> - <heading>When I boot FreeBSD I get ``Missing Operating System''.</heading> + <heading>When I boot FreeBSD I get ``Missing Operating System''.<label id="missing_os"></heading> <p> This is classically a case of FreeBSD and DOS or some other OS conflicting over their ideas of disk <ref id="geometry" @@ -2399,6 +2399,92 @@ drivedata: 0 to reinstall Windows95 (which is a Jealous Operating System, and will bear no other Operating Systems in the Master Boot Record). + <sect1> + <heading>Will a ``dangerously dedicated'' disk endagner my health?</heading> + <p> + The installation procedure allows you to chose two different + modi how to partition your harddisk(s). The default way makes + it compatible with other operating systems on the same machine, + by using fdisk table entries (called ``slices'' in FreeBSD), + with a FreeBSD slice that employs partitions of its own. + Optionally, one can chose to install a boot-selector to switch + between the possible operating systems on the disk(s). + + <p> + Now, while this is certainly the common case for people + coming from a PC background, those people coming more from a + Unix background and who are going to setup a machine just to + run FreeBSD and only FreeBSD, are more used to the classic + Unix way where the operating system owns the entire disks, + from the very first sector through the end. A true fdisk + table isn't of any use in this case, the machine is running + FreeBSD 24 hours per day, 7 days per week, no other operating + system should ever be booted on it. So, if you select + ``A)ll FreeBSD'' in sysinstall's fdisk editor, and answer the + next question with ``No'', you'll get this mode. Note that + this means the BSD bootstrap also forms the MBR for this drive, + so there's no space left for anything like a boot manager. + Don't ever try to install one, or you'll damage the BSD + bootstrap. + + <p> + So why it is called ``dangerous''? A disk in this mode + doesn't contain what normal PC utilities would consider a + valid fdisk table. Depending on how well they have been + designed, they might complain at you once they are getting + in contact with such a disk, or even worse, they might + damage the BSD bootstrap without even asking or notifying + you. Some kind of operating system that is in rather + widespread use on PCs is known for this kind of + user-unfriendliness (of course, it does this in the name of + ``user-friendliness''). At least one Award BIOS that is for + example used in HP Netservers (but not only there) is known + to ignore any harddisk that doesn't have what it believes to + be a valid fdisk table. When it comes to booting, it simply + ignores such a disk drive, advances to the floppy drive, and + barfs at you with just ``Read error''. Very impressive, eh? + They probably also call this ``user-friendly'', who knows? + + <p> + The advantages of this mode are: FreeBSD owns the entire + disk, no need to waste several ficticuous `tracks' for just + nothing but a 1980-aged simplicistic partitioning model + enforcing some artificial and now rather nonsensical + constraints on how this partitioning needs to be done. + These constraints often lead to what might be the biggest + headaches for OS installations on PCs, geometry mismatch + hassles resulting out of two different, redundant ways how + to store the partitioning information in the fdisk table. + See the chapter about <ref id="missing_os" name="Missing + Operating System">. In ``dangerously dedicated'' mode, the + BSD bootstrap starts at sector 0, and this one is the only + sector that always translates into the same C/H/S values, + regardless of which `translation' your BIOS is using for + your disk. Thus, you can also swap disks between + systems/controllers that use a different translation scheme, + without risking that they won't boot anymore. + + <p> + To return a ``dangerously dedicated'' disk for normal PC + use, there are basically two options. The first is, you + write enough NULL bytes over the MBR to make any subsequent + installation believe this to be a blank disk. You can do + this for example with + + <verb> + dd if=/dev/zero of=/dev/rsd0 count=15 + </verb> + + Alternatively, the undocumented DOS command + + <verb> + fdisk /mbr + </verb> + + is supposed to install a new master boot record as well, + thus clobbering the BSD bootstrap. + + <sect1> <heading>How can I add more swap space?</heading>