[SOLVED] Wiki page for GPT disks and booting arch using UEFI

skodabenz · 2010-05-21 15:03:33

Hi guys, I am new to archlinux. I installed archlinux x86_64 just yesterday and I like its customisability. I also like arch wiki. Nowhere else have I seen such extensive documentation, especially about things like HAL, UDEV etc. with proper instructions. Thanks to all archers.

I have installed Archlinux x86_64 in my Dell India Studio 1537 laptop along with Windows 7 Professional x64. Both the OSes boot in UEFI-GPT setup (my UEFI is tianocore.sourceforge.net EDK DUET UEFI64 firmware booting from USB). I boot Archlinux using my own compiled grub2-bzr compiled for both BIOS and UEFI-x64. I have a 1 MB BIOS Boot Partition as required by grub2 for BIOS-GPT booting. My Archlinux system can boot both from bios and from uefi, while Windows can boot only using UEFI.

The official Archlinux installation guide talks about only MBR (or msdos disklabel) partitions and booting from BIOS based systems. With 2TB drives becoming common place and UEFI being implemented (search for Phoenix SecureCore Tiano's 1 second POST operation), I think a proper wiki page describing differences between MBR and GPT, why GPT is better, how to setup arch to boot from GPT. Another page describing steps to setup arch to boot from UEFI (either as a separate page or as an extension of GRUB2 wiki page) is also needed.

Some details regarding Pure GPT (not a Hybrid GPT/MBR setup) and/or UEFI setups :-

Partitioning tools -
GNU Parted for filesystem related tasks
GPT fdisk tool - http://rodsbooks.com/gdisk/ , http://sourceforge.net/projects/gptfdisk/ , pacman -S gdisk (in extra repo) - for non-filesystem related tasks
util-linux-ng fdisk does not support GPT disks

Bootloader - GRUB2 - vanilla grub-legacy does not support GPT and does not support UEFI (Fedora's patched grub-legacy does support both GPT and UEFI) and syslinux does not support GPT (I may be wrong here - seems a gptmbr of syslinux does help in booting from gpt but not sure).

For GRUB2 - Need BIOS Boot Partition to embed GRUB2's core.img in GPT disks - size about 1 MB max - no filesystem
In GPT fdisk partition type code - EF02
In GNU Parted or GParted - bios_grub flag on
For UEFI-GPT booting this special partition is not needed as no embedding takes place. This is needed only in case of BIOS-GPT booting.

Incase of custom kernel configuration - enable CONFIG_EFI_PARTITION for GPT support
CONFIG_EFI for UEFI support (for UEFI even above option required)
CONFIG_EFI_VARS for UEFI Runtime Variables support (optional)

Note: Although GPT is part of UEFI specification, a UEFI system is not needed to boot from/use GPT. BIOS based GPT booting is possible with GRUB2 or Fedora's patched grub-legacy (but not vanilla grub-legacy provided by archlinux). It is also possible to boot Linux in UEFI-MBR setup (again using grub2) but I have not tried it.

Even without UEFI and less than 2TB harddrives, GPT based partitioning has many advantages - secondary GPT header and Partition table, CRC32 checksums. Unique Disk GUID and Filesystem-independent Unique Partition GUIDs, multiple primary partitions (default is 128 partitions, but it can be changed). The only problamatic OS is Windows which does not allow GPT booing unless one has UEFI based system. It allows only UEFI-GPT or BIOS-MBR setups. In linux it just depends on how the bootloader is configured - not a problem with grub2.

I also propose that incase of Auto-prepare Hard Drive, the installer default to GPT for "archlinux only" installs ( ie no dual-boot or triple-boot etc.).

I did not use the official archlinux iso but used archboot 2010.04 R3 as it gave an option of installing to GPT and also provided GRUB2 during bootloader install. I have never edited any wiki page before, thats why I request some one else to start a wiki page with the information given above.

I don't know whether this is the right place, but any Windows (Vista or 7 x64 versions) and Linux dual-boot user who has UEFI-based system with GPT partitioning and wants to get rid of Hybrid MBR setup (to boot Windows) can follow this post http://www.insanelymac.com/forum/lofive … hp/t186440 (outside this forum) - this link describes the way to make Windows boot natively in UEFI-GPT setup. After doing this one can install arch using GRUB2 compiled for UEFI x86_64, and Windows will also see

Last edited by skodabenz (2011-01-30 19:32:48)

hokasch · 2010-05-21 15:26:39

Welcome to arch, skodabenz! Offering documentation on third post - all thumbs up

You could start the wiki page in your user-space with what you have, and then invite others to join working on it. Just register a wiki account, navigate to the page you want to start, for example:

http://wiki.archlinux.org/index.php/User:skodabenz/GPT

and click on "edit this page".

As noted in the other thread, arch's legacy grub is patched for gpt support. I don't know about UEFI, but you can always open a bug report asking for the patches from fedora to be included.

edit: the page from Rod Smith is a great resource. I was absolutely terrified at first by all this screwed up GPT/MBR stuff when I tried triple-booting Arch, Win and OS x, but he really does a great job explaining what it is all about.

Last edited by hokasch (2010-05-21 15:44:08)

skodabenz · 2010-05-22 12:40:39

I created the page in the same link as you mentioned. I have just typed whatever came in my mind. I request someone to edit the page and bring it to the correct wiki format. I have never edited any wiki page so please help me.

http://wiki.archlinux.org/index.php/User:Skodabenz/GPT