Features/Grub2

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Feature Name

GRUB2

Summary

THIS IS VERY VERY EARLY STAGE

This is very early stage, but I'm trying to document the progress here rather than just locally

Switch to using grub2 instead of grub legacy for boot loading an installed x86 system

Owner

• Name: Peter Jones

Current status

• Targeted release: 16
• Last updated: 8/10/2011
• Percentage of completion: 85%

http://koji.fedoraproject.org/koji/buildinfo?buildID=242356 At least probably 10% of this feature is creating and updating the packages to reflect changes in http://ftp.gnu.org/gnu/grub/.

Detailed Description

We currently use what is essentially a fork of GRUB 0.9x in Fedora for a variety of historical reasons. It would be nice to get back to the upstream developed version, even though it is in many ways an entirely new project.

GRUB2 has reached version 1.99 (equivalent to r.c. 3). The upstream wiki can be found at http://grub.enbug.org/ (This was down for me so http://www.gnu.org/software/grub/.)

Benefit to Fedora

There could be new functionality, but that's currently less of the driver.

• • • ---***

Grub (legacy) is no longer supported. Patches are not accepted. Grub2 is also nearing a stable release (14-May-2011 GRUB 1.99) which is something that Grub (legacy) never reached.

Scope

The changes are somewhat localized, but there's a lot to be done. The current status based on the testing I've done so far.

What Currently Works

• MBR Bios booting as chainloaded from grub1 works
• Booting from the MBR works
• Graphics mode works
  • You have to have freetype2-devel installed and build with --enable-mkfont
  • Also had to grab the unifont from http://unifoundry.com/unifont.html
  • Simple hacked up module to load a background image is okay. Could certainly be made better
• Creating /usr/local/etc/defaults/grub (would be /etc, but prefix=/usr/local) allowed me to set the following
  • default timeout, default distro name, default to graphics mode
  • some of this is lame and should get auto-detected (eg, parse /etc/system-release)

Things that still have to be tested/worked on

• EFI mode
• passwords -- Debian and Ubuntu are working on this upstream as of 8 July
• hidden menu support that we use for flicker-less boot
• serial terminal support (with the timeouts)
• bootonce
• Always adding single user entry is not so good -- set GRUB_DISABLE_LINUX_RECOVERY in /etc/default/grub
• Chainloading various versions of Windows
• Auto-detection of Windows and adding it to the config file
• Can we ship the unifont ?
• support for multiple initrds
  • Also, as I had it "built", the font wasn't quite right
• Ensuring all the other features we have and care about are present (if someone wants to make a list of these, it would be helpful)
• Documentation, documentation, documentation...

External things that would need work

• anaconda needs to be able to create the new file. Or at least run grub-mkconf
• grubby to update. Or phase out for grub-updconf?

How To Test

It is very easy to test from Grub Legacy type environment, but we will also need to test from Anaconda/Firstinstall.

From an Installed System with Grub Legacy

This was adapted from http://en.gentoo-wiki.com/wiki/Grub2

The following will automatically generate a GRUB2 configuration file including kernels images within your /boot folder, using the auto configuration scripts in /etc/grub.d, the -o specifices an output file, here the default, /boot/grub2/grub.cfg:

grub2-mkconfig -o /boot/grub2/grub.cfg

Testing With Chain Loading

GRUB2 includes a boot image that's loadable from GRUB Legacy, so you can try it out without wiping out your existing, working MBR. To set up GRUB2 without actually writing to the MBR, run

grub2-install --grub-setup=/bin/true /dev/sda

Writing to the MBR

If that works, you can go on testing to writing to your MBR. Same steps as above, but don't tell grub to run the dummy setup program /bin/true

grub2-install /dev/sda

Congratulations! You've reached the point of no return! If you can't boot now you will need to run a rescue CD

From a DVD with Anaconda

An install DVD can be used to install or repair grub, after setting up a working chroot of your filesystems. From a root console:

1. make a directory to work in:

mkdir /mnt

1. mount your filesystems (device nodes are examples, be sure to fill in your own!):

mount /dev/sda2 /mnt mount /dev/sda1 /mnt/boot

1. bind mount your system filesystems:

mount --bind /dev /mnt/dev mount --bind /proc /mnt/proc mount --bind /sys /mnt/sys

1. enter your chroot

chroot /mnt

You should now be able to install grub2 to your device without interference from the temporary system.

Test matrix here: https://fedoraproject.org/wiki/User:Pjones/Grub2TestMatrix

User Experience

Ultimately, the main thing a user could change is the different config file (grub.cfg vs grub.conf) and the different syntax in the config file. During the normal boot process, the idea should be that it's not that noticeable

Dependencies

We'll have to be sure to update anaconda for the new config file format and also deal with things like grubby (which updates boot loader configs)

Contingency Plan

Keep using GRUB legacy

Documentation

• The only docs right now are at the upstream site, but they're slim at best.

Release Notes

Fedora switched from grub legacy to grub2 in Fedora 16. Grub 2 allows better configuration options, better support for non x86 architectures, scripting and localization support. Grub 2 has new configuration format and and files. Please consult the grub manual for more information.

Comments and Discussion

• See Talk:Features/Grub2

• http://en.gentoo-wiki.com/wiki/Grub2
• https://help.ubuntu.com/community/Grub2
• http://wiki.debian.org/Grub
• http://en.opensuse.org/GRUB
• https://wiki.archlinux.org/index.php/GRUB2
• GRUB 2 bootloader-Full tutorial
• wikipedia-GRUB