Merge lp:~psusi/ubuntu/precise/installation-guide/partitions into lp:ubuntu/precise/installation-guide

[Phillip Susi]

How's that look?

[Colin Watson (cjwatson)]

I think this removes too much information. Although I don't have specific citations for you, I've unfortunately seen even quite recent systems that had trouble booting from later in the disk and required a /boot partition.

Could you keep most of the wording about /boot partitions, and just remove the obsolete bit about partition numbering?

review: Needs Fixing

[Phillip Susi (psusi)]

The documentation itself already said it is only an issue for PCs from circa 1995-1998. Reading the installation guide as a lay person, I'm thinking who cares about PCs from 14 years ago?

By the way, doesn't grub now require lba mode anyhow? So if you did still have an old bios that only does CHS, a /boot partition wouldn't help.

How many recent systems have this kind of trouble? One in a million? Is that enough to justify a section in the installation guide?

[Colin Watson (cjwatson)]

I'm not saying the documentation is correct in all respects, but you
can't just remove that big chunk of text. GRUB can handle CHS to some
extent; and in any case it isn't just CHS, there are other reasons why
you might need /boot to be near the start of the disk.

No, please don't exaggerate. If it were one in a million I very much
doubt I'd have seen multiple examples of this.

If you want a thoroughly modern example, >2TB disks are becoming common,
but in discussions with BIOS people nobody is able to tell me with any
confidence that the weakly-tested support for 64-bit reads using BIOS
calls actually works on a plurality of systems, and thus it's quite
possible that /boot needs to be in the first 2TB of the disk if you're
using GPT with BIOS (which otherwise ought to work fine in most cases)
in order to avoid lurking unreliability. While the reasoning is quite
different from that in the guide at the moment, the ultimate advice is
essentially the same.

Unmerged revisions

40. By Phillip Susi on 2012-02-13

* Remove outdated/incorrect partition information (LP: #704412)
* Add section on using GPT

=== modified file 'debian/changelog'
--- debian/changelog	2011-09-26 16:06:37 +0000
+++ debian/changelog	2012-02-13 20:12:18 +0000
@@ -1,3 +1,10 @@
+installation-guide (20100518ubuntu6) precise; urgency=low
+
+  * Remove outdated/incorrect partition information (LP: #704412)
+  * Add section on using GPT
+
+ -- Phillip Susi <[e-mail]>  Fri, 13 Jan 2012 15:01:07 -0500
+
 installation-guide (20100518ubuntu5) oneiric; urgency=low
 
   * Bump kernelversion to 3.0.

=== modified file 'en/partitioning/partition/x86.xml'
--- en/partitioning/partition/x86.xml	2007-07-23 15:52:44 +0000
+++ en/partitioning/partition/x86.xml	2012-02-13 20:12:18 +0000
@@ -17,8 +17,8 @@
 
 The PC BIOS generally adds additional constraints for disk
 partitioning.  There is a limit to how many <quote>primary</quote> and
-<quote>logical</quote> partitions a drive can contain.  Additionally, with pre
-1994&ndash;98 BIOSes, there are limits to where on the drive the BIOS can boot
+<quote>logical</quote> partitions a drive can contain.  Additionally, with
+very old or buggy BIOSes, there are limits to where on the drive the BIOS can boot
 from.  More information can be found in the
 <ulink url="&url-partition-howto;">Linux Partition HOWTO</ulink> and the
 <ulink url="&url-phoenix-bios-faq-large-disk;">Phoenix BIOS FAQ</ulink>, but
@@ -36,60 +36,24 @@
 drive.
 
 </para><para>
-
-Linux limits the partitions per drive to 15 partitions for SCSI disks
-(3 usable primary partitions, 12 logical partitions), and 63
-partitions on an IDE drive (3 usable primary partitions, 60 logical
-partitions). However the normal Ubuntu system provides
-only 20 devices for partitions, so you may not install on partitions
-higher than 20 unless you first manually create devices for those
-partitions.
-
-</para><para>
-
-If you have a large IDE disk, and are using neither LBA addressing,
-nor overlay drivers (sometimes provided by hard disk manufacturers),
-then the boot partition (the partition containing your kernel image)
-must be placed within the first 1024 cylinders of your hard drive
-(usually around 524 megabytes, without BIOS translation).
-
-</para><para>
-
-This restriction doesn't apply if you have a BIOS newer than around
-1995&ndash;98 (depending on the manufacturer) that supports the <quote>Enhanced
-Disk Drive Support Specification</quote>.  Both Lilo, the Linux loader, and
-Ubuntu's alternative <command>mbr</command> must use the BIOS to read the
-kernel from the disk into RAM.  If the BIOS int 0x13 large disk access
-extensions are found to be present, they will be utilized. Otherwise,
-the legacy disk access interface is used as a fall-back, and it cannot
-be used to address any location on the disk higher than the 1023rd
-cylinder.  Once Linux is booted, no matter what BIOS your computer
-has, these restrictions no longer apply, since Linux does not use the
-BIOS for disk access.
-
-</para><para>
-
-If you have a large disk, you might have to use cylinder translation
-techniques, which you can set from your BIOS setup program, such as
-LBA (Logical Block Addressing) or CHS translation mode (<quote>Large</quote>).
-More information about issues with large disks can be found in the
-<ulink url="&url-large-disk-howto;">Large Disk HOWTO</ulink>.  If you
-are using a cylinder translation scheme, and the BIOS does not support
-the large disk access extensions, then your boot partition has to fit
-within the <emphasis>translated</emphasis> representation of the
-1024th cylinder.
-
-</para><para>
-
-The recommended way of accomplishing this is to create a small (25&ndash;50MB
+The new <quote>GUID Parittion Table</quote> (GPT) can be used instead
+of the <quote>msdos</quote> partition table.  GPT has no extended or
+logical partitions, and supports 128 primary partitions and disks larger
+than 2TB.  GPT was intended to be used on <quote>EFI</quote> based machines.
+Some recent motherboards have an option to boot in EFI or BIOS mode.
+When booting in EFI mode, you must create a small (100MB) boot partition.
+This boot partition <emphasis>must</emphasis> be mounted on <filename>
+/boot/efi</filename>. To boot in BIOS mode, you must create a tiny (1 MB)
+<quote>bios_grub</quote> partition.  Either should be at or near the start of the disk.
+</para><para>
+
+If you have an old/buggy BIOS that can not access the whole disk,
+the recommended way of dealing with this is to create a small (100MB
 should suffice) partition at the beginning of the disk to be used as
 the boot partition, and then create whatever other partitions you wish
 to have, in the remaining area.  This boot partition
 <emphasis>must</emphasis> be mounted on <filename>/boot</filename>,
 since that is the directory where the Linux kernel(s) will be stored.
-This configuration will work on any system, regardless of whether LBA
-or large disk CHS translation is used, and regardless of whether your
-BIOS supports the large disk access extensions.
 
 </para>
   </sect2>