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booting from USB

By Jim Mercer @jimmercer
    2026-08-03 20:55:14.205Z

    i downloaded the image from the link on the main page.

    i put it on a USB stick using rufus/windows (but it did not prompt for "DD" mode).

    it wouldn't boot off the USB, until i set it to EUFI boot from flash.
    then it booted, but it kernel panic'd trying to mount the CD.

    i tried balena-etcher/windows, but it does not recognize the bootable image as something it can burn.

    i tried a raw dd of the image to the USB stick (on FreeBSD) using:
    dd if=/tmp/kariosbsd-14.3-custom.iso of=/dev/da1 bs=1M status=progress conv=sync

    the bios doesn't recognize this as a bootable USB image (it doesn't even appear in the boot menu of the bios).

    this is using the image from:
    https://s3.us-east-1.amazonaws.com/amzn-kariosbsd-14.3/kariosbsd-14.3-custom.iso

    what is the recommended method of burning the iso image to a USB flash?

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    • 3 replies
    1. J
      Jim Mercer @jimmercer
        2026-08-03 21:01:11.242Z2026-08-03 21:24:31.297Z

        note:

        the target is an older Supermicro server, series X9, which doesn't support booting from virtual media (sadly).

        the targe did boot from a routine USB stick created via rufus, with FreeBSD 15 memstick.img.

        Reply
        1. J
          In reply tojimmercer⬆:
          Jim Mercer @jimmercer
            2026-08-03 21:28:01.365Z

            i managed to convert the image to a bootable .img file, which i burned with dd on freebsd.
            (and burned without issue, using rufus/windows)

            both booted without issue.

            as root:

            su -
            mkdir /tmp/kosos-img
            cd /tmp/kosos-img
            fetch https://s3.us-east-1.amazonaws.com/amzn-kariosbsd-14.3/kariosbsd-14.3-custom.iso
            truncate -s 2000M freebsd_memstick.img
            mdconfig -a -t vnode -f freebsd_memstick.img
            gpart create -s mbr md0
            gpart add -t freebsd md0
            gpart set -a active -i 1 md0
            gpart create -s bsd md0s1
            gpart add -t freebsd-ufs md0s1
            gpart bootcode -b /boot/mbr md0
            gpart bootcode -b /boot/boot md0s1
            newfs /dev/md0s1a
            mkdir -p ./src_iso ./dst_img
            mdconfig -a -t vnode -f ./kariosbsd-14.3-custom.iso -u 1
            mount -t cd9660 /dev/md1 ./src_iso
            mount /dev/md0s1a ./dst_img
            cp -Rpv ./src_iso/ ./dst_img/
            rm -f ./dst_img/etc/fstab
            echo '/dev/da0s1a / ufs rw 1 1' | tee ./dst_img/etc/fstab
            umount ./dst_img
            umount ./src_iso
            mdconfig -d -u 1
            mdconfig -d -u 0
            ls -la
            mv freebsd_memstick.img kariosbsd-14.3-custom.img

            dd if=./kariosbsd-14.3-custom.img of=/dev/da1 bs=1M status=progress conv=sync

            Reply
            1. K
              In reply tojimmercer⬆:
              @kuljeet
                2026-08-04 17:36:36.449Z

                Hi Jim,

                Thanks so much for circling back and posting your solution — and sorry for the trouble getting there. You're right that the ISO itself wasn't booting properly; we've seen the same failure to boot correctly from virtual media on our end, so this isn't just an X9-specific issue. We've tested on newer Supermicro models but hadn't yet tested against the X9 series specifically, so your report is genuinely useful data for us.

                Glad the workaround — converting to a proper memstick image via mdconfig/gpart/newfs, then writing with dd or rufus — got you booting cleanly on both paths in the meantime. We'll use this to look at fixing the ISO boot behavior itself rather than leaving this as a workaround.

                If you have a few minutes, we'd love any additional feedback — on the image, the docs, or anything else that would've made this easier to figure out. It really helps us prioritize fixes.

                Thanks again for taking the time to document and share this!

                Best,
                Kuljeet Singh Bhengura

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