kexec-fast-reboot

Reboot your server in seconds, not minutes!

Overview

I was looking for a solution to reboot our HP Proliants without having to go through the agonizing long BIOS startup sequence. At first, I found https://github.com/error10/kexec-reboot which worked great on my dev server but our production servers use ZFS and it was not able to parse the grub config. I looked long and hard at various github projects but none of them were able to parse the grub config correctly.... Until I found https://github.com/avagin/kexec-reboot. It uses the grubby utility which does grub and grub2 parsing "professionally" and it finally worked.

Kexec lets you boot your Linux kernel into another kernel without going through the hardware reset and reinitialization performed by your system BIOS or firmware. Since this process can take several minutes, being able to skip it reduces your downtime.

The problem with kexec is that it is an entirely manual process, requiring you to copy and paste the right kernel, initrd and command line arguments, and hope you got everything right.

kexec-fast-reboot aims to automate staging a kernel for kexec, so that you can reboot more quickly and accurately.

Result: Reboot your server in seconds, not minutes!

I forked it because it did not seem to be maintained and had a couple of pull requests that seemed useful. Also I wanted a repo I could pull down that would just "work" for our servers. I renamed the project to kexec-fast-reboot as I wanted a unique name that I could find on github. I renamed the executable from kreboot to fast-reboot to align with this change.

Prerequisites

kexec-reboot requires the following packages to be installed:

kexec-tools 2.0.0 or higher, for /sbin/kexec
grubby from https://github.com/rhboot/grubby or you package manager

I am on Debian and I could not find a way to install grubby via apt. So I had to compile it. It's very straight forward. Simply make && make install will do. I did need to install libpopt-dev and libblkid-dev so it would compile.

I have included my compiled version of grubby in this repo, mainly for my own use, so I could pull it down whenever I needed it. YMMV on different systems and architectures of course as far as the provided grubby is concerend.

In addition, the system must use grub to boot, as kexec-fast-reboot reads the grub configuration to determine what kernels are available. Both grub 1 and 2, BIOS and UEFI boot should work. But please test before blindly copying this onto a production machine.

Install

Git clone this project, cd into it and run make install and it will put it all in the right places (it does not compile anything, its just a bash script).

Use make uninstall to remove it. Alternatively just copy the bash script somewhere in your path.

If you want to use the included grubby copy it somewhere in your path. /ust/local/bin seems like a good choice.

Usage

Options are:

Usage: fast-reboot [option ...] [kernel|boot-index]
    --wait, -w N    Wait N seconds before reboot (default 10)
    --nowait        Don't wait, reboot immediately
    --nodetach, -n  Do not detach. By default it runs --detach 3
    --detach, -d N  Schedule reboot in N seconds and return
    --help, -h      Show this help message
    --kargs, k      Additional kernel arguments

Examples

This is a screencast made by the original project. It uses kreboot as the command but otherwise it's the same.