There are two ways to speed up system boot:

  1. Remove cruft from the boot sequence (parallelizing init scripts, readahead, removing modules, etc.)
  2. Bypass the boot sequence completely to boot into a pre-saved image

This spec talks about the second technique. The first one is already being addressed in other teams/sessions.

Release Note

The x86 boot sequence is quite fragile with the multitude of (buggy) BIOSes that need to be supported. Hence the grub fast boot changes should not be the default option, but rather enabled explicitly by the user.


Netbook users and OEMs are asking for faster boot times so that the (mobile) devices are quickly usable. The idea is that these devices should have the response times of a traditional mobile device such as a mobile phone and the functionality of a laptop.

Use Cases

  1. Alice is attending a conference. Typical of conferences, there are very few power sockets. While listening to the sessions, Alice would like to take notes, check email and then close the lid and go back to listening. She repeats this many times during the day. In order to save battery, the machine should suspend/hibernate when the lid is closed and resume quickly when it is opened. The battery should last the whole day on a single charge.

  2. Bob manages a server farm that guarantees 99.99% uptime. That means 52 minutes of downtime allowed per year. Considering some of these machines take 10+ minutes to boot, every second saved counts.
  3. Charlie manages a 1000-seat Linux desktop installation. A majority of his users do not power-off their computer at night because they want an instant-on experience in the morning. Some of the more conscientious users suspend the machine, but it still draws some power.

Alice needs her laptop to save power and become usable quickly. Suspend/Resume (STR) ought to give her that. If STR doesn't give a full days battery life, fast boot might become more attractive.

Bob could definitely use fast boot, but only if it supported his enterprise hardware configurations - so LVM and RAID support need to be thought about.

With Fast Boot, Charlie could mandate compulsory shutdowns since users would be more amenable to sub-30s boots.


Need to verify numbers from Intrepid

Here are typical boot/suspend/hibernate/resume numbers from a laptop:

Shutdown numbers

Startup numbers



Grub Fast Resume




Snapshot boot for ARM

Test/Demo Plan

Unresolved issues

BoF agenda and discussion



KernelTeam/Specs/FasterBootFromImage (last edited 2008-12-06 18:15:34 by 216)