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Reboot Linux Faster Using kexec
An anonymous reader writes "Even if your work doesn't require you to reboot your Linux machine several times a day, waiting for a system to reboot can be a real drag. Enter kexec. Essentially, kexec is a fast reboot feature that lets you reboot to a new Linux kernel -- without having to go through a bootloader. Faster reboot is a benefit even when uptime isn't mission-critical -- and a lifesaver for kernel and system software developers who need to reboot their machines several times a day. Kexec is currently available on the x86 32-bit platform only."
For me what takes the longest isn't the bootloader, it's the starting and stopping of services. This is still cool though.
Chaos is Divine *
While there is a marginal speedup in skipping the BIOS startup, the main benefit for me is the ability to choose which kernel to boot remotely. I don't have physical access to my colocated system and permanently setting GRUB to boot a new kernel is a bit scary. With kexec I can choose which kernel to boot from ssh. If it doesn't work out I don't have to pay the colo people to reinstall the box. They just hit the reset button :)
I normally use FreeBSD. But recently I took a Linux device drivers class. The first thing I noticed was the extremely slow booting of Linux. Why?
Under FreeBSD it takes about one second from the boot manager handing off to the root partition to start seeing device probing messages. But under Linux the same thing takes about twenty seconds. From appearances, it seems that the root partition LILO is merely loading the kernel, but there's no way that should take twenty seconds. Can it?
Don't blame me, I didn't vote for either of them!
In NetBSD kloader(4) does a similar job. It is used on HPC and game console ports.