A recent blog post about a user who was having trouble installing Ubuntu on an HP machine, sparked off an urban legend that UEFI secure boot is blocking installs of Linux. To calm FUD with facts: the secure boot feature hasn’t been implemented and shipped yet on any hardware. It was introduced in the 2.3.1 version of the UEFI specification, which was released in April 2011. Hardware with secure boot will start shipping next year.
It’s important to distinguish between UEFI in general and the new secure boot feature. UEFI has been around for a while, starting its life as the “Intel Boot Initiative” in the late ’90s. It has a number of advantages over old BIOS, including substantially faster boot times, the ability to boot from a drive larger than 2.2 TB, and the ability to handle more than 4 partitions on a drive. The UEFI specification is developed by the members of the UEFI Forum, a non-profit trade organization with various levels of free and paid memberships. UEFI is not a problem for Linux. At the UEFI Plugfest in Taipei last week, Alex Hung (Canonical) tested Ubuntu 11.10 on a number of machines, with success even on pre-release chipsets. The few failures seemed to be related to displays, and not particularly to UEFI.
The secure boot feature of UEFI is a concern for Linux, but not because of the specification. The features outlined in the 2.3.1 specification are general enough to easily accommodate the needs of Linux. But, within the range of possible implementations from that specification, some alternatives could cause problems for Linux. For full details, I recommend reading the two whitepapers released by Canonical and Red Hat and by The Linux Foundation. The short version is that secure boot uses signed code in the boot path in much the same way you might use a GPG signed email message: to verify that it came from someone you know and trust. The beneficial ways of implementing this feature allow the individual (or administrator) who owns the machine to add new keys to their list, so they get to choose who to trust and who not to trust. The harmful ways of implementing this feature don’t allow the user to change the keys, or disable the secure boot feature, which means they can’t boot anything that isn’t explicitly approved by the hardware manufacturer (or OS vendor). This would mean users couldn’t just download and install any old image of Debian, Fedora, Red Hat, SuSE, Ubuntu, etc. So, there’s real potential for a future problem here, but we’re not there yet. At this point, it’s a matter of encouraging the hardware companies to choose the beneficial path.
I’ve been chatting with the Ubuntu user who had the install problem, to see if we can find the real bug. It’s a friend’s machine rather than his own, so he doesn’t have easy access to it. I’ve arranged to get access to a similar machine next week to play with it. I’ll post back here if I find anything useful or interesting.
Mythbusters – UEFI and Linux (Part 2) « Allison Randal