Date: Wed, 27 Feb 2002 23:57:31 +0000 (GMT) From: Andrew Gordon <arg-bsd@arg1.demon.co.uk> To: "Clark C . Evans" <cce@clarkevans.com> Cc: <freebsd-small@FreeBSD.ORG> Subject: Re: read-only CD-ROM boot partition for webfarm? Message-ID: <20020227233523.G89345-100000@server.arg.sj.co.uk> In-Reply-To: <20020227181434.A17592@doublegemini.com>
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On Wed, 27 Feb 2002, Clark C . Evans wrote: > Hello. I'm building a webfarm and other than the apache > configuration and webpages, the core operating system and > /usr partition is/should-be relatively static (scp used to > update stuff in a /data partition). I'm using vinum to > mirror /data. > > How hard would it be to make a bootable CD-ROM image with > everything on it except the data, log-files, etc? Fairly easy. You have two options: the old way, where you create a floppy image containing your kernel, /boot/loader and a suitable /boot/loder.rc to make it mount root from the CD-ROM; or the new way using 'non-emulation' booting and the /boot/cdboot which can read the kernel directly from the iso9660 filesystem on the CD. Apart from that, the CD just needs to contain a fairly normal root filesystem, with some tweaks to deal with the read-onlyness. I like to use the /etc/rc.diskless stuff (with /etc/rc hacked to invoke it despite not being a netboot), as this does nearly everything needed (MFS filesystems for things that need to be read-write). However, in your case where you have some read-write filesystems available, this may not be necessary. To get things going, I like to temporarily fit a normal harddrive to the machine so that I can do a normal install, tweak so that everything is working as required without doing any writing, then copy the resulting system to CD-ROM: unless you are going to get it right first time, this gives a much faster edit/reboot/debug cycle than burning CD-RWs. One caveat with your overall plan: typical CD drives don't last very long under heavy access. In the applications where I have used CD booting, this isn't a problem: with a fairly static application, I can provide enough RAM that the entire working set fits in RAM, so the CD just spins the first time that the operator visits each part of the program, then everything runs from RAM for days at a time until reboot. In your situation, this may be harder to achieve. You may need to arrange that the main applications get copied to an MFS filesystem or otherwise locked into RAM to avoid thrashing the CD drive. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-small" in the body of the message
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