Dev/Embedded/Rootfs/Devuan/FromScratch

Using debootstrap

Part 1 : on any computer (running debian based distribution of course)

Use the following debootstrap command :

debootstrap --foreign --arch=arm64 --include=vim,bsdutils,openssh-client,openssh-server --exclude=ed,nano,tasksel,tasksel-data,vim-tiny --verbose ceres rootfs/ http://fr.deb.devuan.org/merged

You can add some of these (and many more) depending on your needs :

locales,file,net-tools,ca-certificates,bzip2,devuan-keyring,debian-archive-keyring,debian-keyring,diffutils,findutils,iptables,isc-dhcp-client,netbase,ntp,openssh-sftp-server,screen,wireless-tools,minicom

Do not add udev !
It may be possible to add eudev, but somtimes the second stage fails when it is included, so it may be better to add it after the second stage successfully completed (with apt-get install).

Part 2 : on the target

Solution 1 : "init=" kernel parameter

Add "init=/bin/bash" to your kernel command line (in the bootloader configuration), to get something like this (modify and/or add any required option according to your system) :

console=ttyS0,115200n8 root=/dev/mmcblk0p2 rw init=/bin/bash

And once you get the prompt, execute the end of the installation :

export PATH=/usr/sbin:/usr/bin:/sbin:/bin
mount -o remount,rw /
mount -t proc none /proc
mount -t sysfs none /sys
mountpoint -q /dev || mount -t devtmpfs none /dev
[ ! -d /dev/pts ] && mkdir /dev/pts
mount -t devpts none /dev/pts
trap -- '' SIGUSR1 # Avoid getting killed by SIGUSR1 sent to restart init
/debootstrap/debootstrap --second-stage

You should then set the root password, and then stop the board (halt -f).

Solution 2 : mount on existing system

If you've got a running system (any kind of Linux distribution or custom image) for your board and have a solution to mount some external device or remote filesystem on it, then you can use it to run the second stage :

mount /path/to/remote/or/external /mnt/tmp
mount -o bind /proc /mnt/tmp/proc
mount -o bind /sys /mnt/tmp/sys
mount -o bind /dev /mnt/tmp/dev
mount -o bind /dev/pts /mnt/tmp/dev/pts
chroot /mnt/tmp /bin/bash
export PATH=/usr/sbin:/usr/bin:/sbin:/bin
/debootstrap/debootstrap --second-stage

Part 3 : Config

Before rebooting, you must modify inittab in order to get a login prompt :

T0:12345:respawn:/sbin/getty -L ttyS0 115200 vt100

And reboot the board once the process has completed.

Using multistrap

Multistrap is a tool that does essentially the same job as debootstrap using an entirely different method, and then extends the functionality to support automated creation of complete, bootable, root filesystems.

Its main limitation compared to debootstrap is that it uses apt and dpkg directly so can only work on a debian system - debootstrap depends on nothing but shell, wget, binutils and thus can run pretty-much anywhere.

Part 1 : on the host

Install multistrap and refer to information from Multistrap debian wiki in order to create your configuration file.

Warning, in order to avoid a lengthy second stage I recomend adding "addimportant=true" in the "General" section of the configuration file.

Then proceed with the first part of the installation :

multistrap -a armhf -d rootfs/ -f my.config.multistrap

Of course set architecture and destination directory according to your needs (this can be done in the configuration file too).

Part 2 : on the target

You must then complete the installation on the target :

mount -o remount,rw /
mount -t proc none /proc
mount -t sysfs none /sys
mount -t devtmpfs none /dev
[ ! -d /dev/pts ] && mkdir /dev/pts
mount -t devpts none /dev/pts
export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true
export LC_ALL=C LANGUAGE=C LANG=C 
dpkg --configure -a

Another Way using live-build

Another solution is presented here : Debian on BeagleBone.

This solution uses live-build and qemu.