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."

Comments

Avoid BIOS

[crow]

Rebooting a box that has SCSI drives means that the BIOS does a scan of the SCSI bus that takes a while, and then the new kernel does the same thing. That's the slowest part of my boot process, and it looks like kexec will bypass the BIOS half of it.

Re:Avoid BIOS

[cyb97]

usually the slowest part of booting a scsi-kernel is "waiting for scsi-devices to settle". Which is usually set to 15s for quite a few drivers in the kernel. Bumping that down to a resonably low number like 2-3 s (usually enough for modern devices, would skimp 10-13s of you boot-time ;-)

BIOS

[ggeens]

The boot loader spends most of its time waiting for the user to press a key, so they can enter custom boot parameters. If you set the timeout to 0 in LILO or GRUB, loading the kernel happens almost instantly.

The BIOS startup routine is longer, especially if you have a SCSI card. (I have 2 of those in my machine, and they account for most of the wait during startup.)

Quicker reboots?

[sweede]

If you read the article, it says that kexec doesnt do a normal,clean shutdown, so you have to stop all running programs and unmount all partitions before running kexec to do a reboot.

When i boot into linux, it takes longer to start up services than it does to go through the BIOS, SATA raid controller BIOS, grub's 3 second time out, and the loading of the linux kernel (before initd takes over).

however, this program is still in ints infancy and no doubt someone will create an initd that can utilize kexec in a run level for rebooting without a full shutdown. But I dont think it will be that much quicker.