Date: Tue, 12 Apr 2016 08:19:30 -0600 From: Ian Lepore <ian@freebsd.org> To: Tim Kientzle <tim@kientzle.com>, Hal Murray <hmurray@megapathdsl.net> Cc: freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: Booting FreeBSD on BeagleBone Black from microSD by default Message-ID: <1460470770.52955.14.camel@freebsd.org> In-Reply-To: <3BC5A04D-79DD-4820-A44F-B0A921D2FAA9@kientzle.com> References: <20160411040655.632D3406076@ip-64-139-1-69.sjc.megapath.net> <3BC5A04D-79DD-4820-A44F-B0A921D2FAA9@kientzle.com>
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On Mon, 2016-04-11 at 06:33 -0700, Tim Kientzle wrote: > > On Apr 10, 2016, at 9:06 PM, Hal Murray <hmurray@megapathdsl.net> > > wrote: > > > > > > Does anybody have the recipe for setting things up so that power on > > boots > > from the microSD card without holding down the button? > > If the ROM cannot boot from eMMC, it will try to boot from microSD. > > The easiest way to make the eMMC not bootable is to zero out the > boot sectors using dd: > > dd if=/dev/zero of=<eMMC device> count=100 > > Of course, this makes the eMMC entirely unusable. I think you > can then reformat the eMMC (make sure it does not have a FAT > partition and does not have boot blocks) so it can be used without > the ROM trying to boot from it. > > This way, the ROM will load U-Boot from microSD. > > > > > I'm pretty sure it will be simple after I know how to do it. > > Google found info on the idea, but I couldn't find the file that > > needs editing. It's off in uBoot land. > > Even if the ROM loads U-Boot from eMMC, the default Linux > U-Boot setup on the eMMC can be configured to then load > the Linux kernel from microSD. > > If you install the FreeBSD version of U-Boot to eMMC, you might be > able to > do the same thing. Personally, I find the recipe above much > simpler. > > Cheers, > > Tim No need to zero out the onboard emmc or mess with its too-complicated linux-centric env vars... The AM335x ROM boot code loads u-boot from the first FAT partition it finds with the active/bootable flag set. Normally that's the emmc, but you can turn it off and then it'll look for a partition on the external sdcard. Once you've booted to freebsd normally, do gpart unset -a active -i 1 mmcsd1 And now it will boot from the sdcard unless you turn the active flag back on on the emmc. - Ian
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