phaq

You accidentally deleted your production kernel?
Both your new and backup kernel are trash?

No worries. You could always use a FreeBSD setup or bootonly CD to load a fallback kernel from there.
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Building pxelinux and memdisk on FreeBSD is not as straight forward as on Linux. A fair amount of additional handwork is involved.

But don’t worry, all steps required to master this task are outlined below.
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Usually ISO’s of most Linux distros use isolinux as boot loader, so these may be served up easily for pxe bootstrap through pxelinux/memdisk.

For FreeBSD this does not hold true, so the vanilla ISO’s must be converted before they can be bootstrapped.
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FreeBSD comes with support for multiple software RAID implementations to date.

• ata, which is not really a RAID toolkit but the ata device driver itself.Nevertheless it provides sort of RAID functionality by also interfacing to popular low-end RAID controllers, sometimes also referred to as Fake-RAID controller (highpoint, promise and alike).
  It has support for enabling RAID on non-RAID capable ata controllers, too.ata is IMHO the worst RAID solution out there, and as such should be avoided at any cost. Please read as I’m writing: I’m not telling you the ata driver is bad, but I think it shouldn’t tamper with RAID.
  RAID should never be implemented by means of a device driver which does some scary magic inside. A real RAID controller (hardware RAID) or a volume manager (software RAID) should be used instead.
• ccd, the concatenated disk driver, used to be a standalone framework in previous FreeBSD versions. It has been integrated with geom (geom_ccd) in FreeBSD 5 and IMHO seems only to exist for historical and backward compatibility reasons by today.
• vinum was also a standalone RAID framework in previous FreeBSD versions. It too was merged into geom (geom_vinum) in FreeBSD 5.
• geom, which is basically an I/O abstraction layer which serves as stackable framework to multiple subsystems like vinum volume manager (which does jbod, raid 0, raid 1, raid 5 and combinations thereof), mirror (which does raid1), stripe (raid0), and many others.geom provides both functionality and reliability in a proper implementation. I think it might outrun big players like Veritas Volume Manager one day.

So what I’m going to do is a performance comparison (benchmark) of the different geom classes providing RAID1 (mirroring), RAID0 (striping) and RAID10 functionality.
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It has been some time now since development on Debian GNU/kFreeBSD started, which aims at bringing together the FreeBSD kernel with a GNU userland.

There exists a similar implementation called Gentoo GNU/kFreeBSD, although I had no time yet to review it.
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This article should have been published already last month, unfortunately the draft was left forgotten for a while in my mailbox.

As some may remember I published two articles on how to setup GEOM disk mirroring on alpha and sparc earlier this year. These articles were originally based upon Ralf Engelschalls disk mirroring howto.

I had installed GEOM disk mirrors on various occasions since then, though I always felt that converting to a GEOM mirror like that involved too much work.

So I went on to find a better and faster way to achieve the task and I found one.
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Symptoms

The FreeBSD boot loader seems to hang at startup. The system will not respond and not boot.
Either nothing or one of the following may be printed on the system console:

|

or

boot: -D

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