Date: Sat, 28 Jun 2014 21:11:05 -0500 From: CyberLeo Kitsana <cyberleo@cyberleo.net> To: "questions@freebsd.org" <questions@freebsd.org>, paul beard <paulbeard@gmail.com> Subject: Re: what should uname -v be telling me here? Message-ID: <53AF75B9.6060107@cyberleo.net> In-Reply-To: <44y4wi3v5x.fsf@be-well.ilk.org> References: <CAMtcK2rBDWwu1=4DbKGB_4kDdi5Fz9Mq3%2Bzf_Ph9jTmrCLZpSg@mail.gmail.com> <44lhsi5ugm.fsf@be-well.ilk.org> <CAMtcK2rZzJPaWBnuZ6s2iZyg4_XjE62JBFTo=iUd%2BT_r4_zoew@mail.gmail.com> <20140627223650.25210a53.freebsd@edvax.de> <CAMtcK2rh3tSF6brU_JxA1%2Btzzuv8SsEoHf_oxAhcW95NRRpKjQ@mail.gmail.com> <44y4wi3v5x.fsf@be-well.ilk.org>
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On 06/27/2014 04:22 PM, Lowell Gilbert wrote: > paul beard <paulbeard@gmail.com> writes: > >> On Fri, Jun 27, 2014 at 1:36 PM, Polytropon <freebsd@edvax.de> wrote: >>> You need to find out where /boot resides (in my case, >>> it's on ad4s1a, which is mounted at /) to identify the boot >>> device (or to be precise, the device the kernel has been read >>> from). >> >> >> I keep thinking this should be something you ought to be able to >> discover without being on console. I realize the BIOS can't be >> interrogated but if I knew that the active kernel was ad3:/boot/kernel >> or ad2:/boot/kernel, it would be useful. Kind of surprised that >> doesn't appear anywhere in dmesg or that it can't be read out of >> somewhere. > > The boot procedure has to load and boot the kernel without having the > kernel available to create the device nomenclature. [Kind of obvious, > if you think about it.] So interrogating the firmware is the only way > the kernel *could* know where it was booted from. That's impossible > in the BIOS world, and even if there were a table indicating it in an > ACPI table, that would only tell you which disk the bootloader came > from, which isn't necessarily where the kernel came from. Another bit of information is available if you peek at what loader(8) told the kernel, via kenv(1). >From a box booting UFS: ----8<---- # kenv ... currdev="disk0s4a:" loaddev="disk0s4a:" kernelname="/boot/10.0p6-GENERIC/kernel" ... ----8<---- And from one booting ZFS: ----8<---- # kenv ... currdev="zfs:paka/root/10.0:" loaddev="zfs:paka/root/10.0:" kernelname="/boot/10.0p6-PAKA/kernel" ... ----8<---- -- Fuzzy love, -CyberLeo Technical Administrator CyberLeo.Net Webhosting http://www.CyberLeo.Net <CyberLeo@CyberLeo.Net> Furry Peace! - http://www.fur.com/peace/
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