Date: Wed, 23 Jan 2013 02:48:29 +0000 (UTC) From: Eitan Adler <eadler@FreeBSD.org> To: doc-committers@freebsd.org, svn-doc-all@freebsd.org, svn-doc-head@freebsd.org Subject: svn commit: r40723 - head/en_US.ISO8859-1/books/faq Message-ID: <201301230248.r0N2mTiX017882@svn.freebsd.org>
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Author: eadler Date: Wed Jan 23 02:48:28 2013 New Revision: 40723 URL: http://svnweb.freebsd.org/changeset/doc/40723 Log: Wes gesund obsolete section: dangerously-dedicated Noted by: nwhitehorn Aproved by: bcr (mentor, implicit) Modified: head/en_US.ISO8859-1/books/faq/book.xml Modified: head/en_US.ISO8859-1/books/faq/book.xml ============================================================================== --- head/en_US.ISO8859-1/books/faq/book.xml Wed Jan 23 02:42:58 2013 (r40722) +++ head/en_US.ISO8859-1/books/faq/book.xml Wed Jan 23 02:48:28 2013 (r40723) @@ -3550,110 +3550,6 @@ kern.sched.name: ULE</screen> </qandaentry> <qandaentry> - <question id="dangerously-dedicated"> - <para>Will a <quote>dangerously dedicated</quote> disk - endanger my health?</para> - </question> - - <answer> - <para><anchor id="dedicate"/>The installation procedure allows - you to chose two different methods in partitioning your hard - disk(s). The default way makes it compatible with other - operating systems on the same machine, by using - &man.fdisk.8; table entries (called <quote>slices</quote> in - &os;), with a &os; 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). The alternative uses the entire disk for &os;, and - makes no attempt to be compatible with other operating - systems.</para> - - <para>So why it is called <quote>dangerous</quote>? A disk in - this mode does not contain what normal PC utilities would - consider a valid &man.fdisk.8; 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. In addition, the <quote>dangerously - dedicated</quote> disk's layout is known to confuse some - BIOSes. - Symptoms of this confusion include the <errorname>read - error</errorname> message printed by the &os; bootstrap when - it cannot find itself, as well as system lockups when - booting.</para> - - <para>Why have this mode at all then? It only saves a few - kbytes of disk space, and it can cause real problems for a new - installation. <quote>Dangerously dedicated</quote> mode's - origins lie in a desire to avoid one of the most common - problems plaguing new &os; installers — matching the - BIOS <quote>geometry</quote> numbers for a disk to the disk - itself.</para> - - <para><quote>Geometry</quote> is an outdated concept, but one - still at the heart of the PC's BIOS and its interaction with - disks. When the &os; installer creates slices, it has to - record the location of these slices on the disk in a fashion - that corresponds with the way the BIOS expects to find them. - If it gets it wrong, you will not be able to boot.</para> - - <para><quote>Dangerously dedicated</quote> mode tries to work - around this by making the problem simpler. In some cases, - it gets it right. But it is meant to be used as a - last-ditch alternative — there are better ways to - solve the problem 99 times out of 100.</para> - - <para>So, how do you avoid the need for <quote>DD</quote> mode - when you are installing? Start by making a note of the - geometry that your BIOS claims to be using for your disks. - You can arrange to have the kernel print this as it boots by - specifying <option>-v</option> at the - <literal>boot:</literal> prompt, or using - <command>boot -v</command> in the loader. Just before the - installer starts, the kernel will print a list of BIOS - geometries. Do not panic — wait for the installer to - start and then use scrollback to read the numbers. - Typically the BIOS disk units will be in the same order that - &os; lists your disks, first IDE, then SCSI.</para> - - <para>When you are slicing up your disk, check that the disk - geometry displayed in the FDISK screen is correct (i.e., it - matches the BIOS numbers); if it is wrong, use - <keycap>G</keycap> to fix it. You may have to do this - if there is absolutely nothing on the disk, or if the disk - has been moved from another system. Note that this is only - an issue with the disk that you are going to boot from; &os; - will sort itself out just fine with any other disks you may - have.</para> - - <para>Once you have got the BIOS and &os; agreeing about the - geometry of the disk, your problems are almost guaranteed to - be over, and with no need for <quote>DD</quote> mode at all. - If, however, you are still greeted with the dreaded - <errorname>read error</errorname> message when you try to - boot, it is time to cross your fingers and go for it — there - is nothing left to lose.</para> - - <para>To return a <quote>dangerously dedicated</quote> 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 the following - command:</para> - - <screen>&prompt.root; <userinput>dd if=/dev/zero of=/dev/<replaceable>rda0</replaceable> count=15</userinput></screen> - - <para>Alternatively, the undocumented DOS - <quote>feature</quote></para> - - <screen><prompt>C:\></prompt> <userinput>fdisk /mbr</userinput></screen> - - <para>will to install a new master boot record as well, thus - clobbering the BSD bootstrap.</para> - </answer> - </qandaentry> - - <qandaentry> <question id="safe-softupdates"> <para>Which partitions can safely use Soft Updates? I have heard that Soft Updates on <filename class="directory">/</filename> can cause
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