Bootable Debian USB

Umm. Somehow I thought this would be easier than learning about live-build. Probably I was wrong. There are probably many better tutorials on the web.

Two useful observations: zeroing the key can eliminate mysterious grub errors, and systemd-nspawn is pretty handy. One thing that should have been obvious, but wasn't to me is that it's easier to install grub onto a device outside of any container.

Find device

 $ dmesg

Count sectors

 # fdisk -l /dev/sdx

Assume that every command after here is dangerous.

Zero it out. This is overkill for a fresh key, but fixed a problem with reusing a stick that had a previous live distro installed on it.

 # dd if=/dev/zero of=/dev/sdx bs=1048576 count=$count

Where $count is calculated by dividing the sector count by 2048.

Make file system. There are lots of options. I eventually used parted

 # parted

 (parted) mklabel msdos
 (parted) mkpart primary ext2 1 -1
 (parted) set 1 boot on
 (parted) quit

Make a file system

 # mkfs.ext2 /dev/sdx1
 # mount /dev/sdx1 /mnt

Install the base system

 # debootstrap --variant=minbase jessie /mnt http://httpredir.debian.org/debian/

Install grub (no chroot needed)

 # grub-install --boot-directory /mnt/boot /dev/sdx1

Set a root password

 # chroot /mnt
 # passwd root
 # exit

create up fstab

# blkid -p /dev/sdc1 | cut -f2 -d' ' > /mnt/etc/fstab

Now edit to fix syntax, tell ext2, etc...

Now switch to system-nspawn, to avoid boring bind mounting, etc..

# systemd-nspawn -b -D /mnt

EDIT: fixed block size of dd, based on suggestion of tg. EDIT2: fixed count to match block size