Requirements

  1. An x86_64 machine with Ubuntu or another Linux distribution installed.
  2. debootstrap tool.
  3. Internet connection.
  4. Basic knowledge of using the terminal.

Steps to Create Ubuntu 20.04 Rootfs for ARMhf

1. Install Required Tools

First, ensure that debootstrap and qemu-user-static are installed. qemu-user-static allows you to run ARM binaries on your x86_64 machine.

sudo apt update
sudo apt install debootstrap qemu-user-static

2. Create a Directory for the Rootfs

Create a directory where the root filesystem will be built.

mkdir -p ~/ubuntu-armhf-rootfs

3. Run Debootstrap

Use debootstrap to create the root filesystem. Specify the architecture (armhf), the Ubuntu release (focal), and the target directory.

sudo debootstrap --arch=armhf --foreign focal ./ubuntu-armhf-rootfs https://mirrors.bfsu.edu.cn/ubuntu-ports/

4. Copy QEMU Binary

Copy the qemu-arm-static binary into the usr/bin directory of the new rootfs to enable emulation.

sudo cp /usr/bin/qemu-arm-static ./ubuntu-armhf-rootfs/usr/bin/

5. Chroot into the New Rootfs

Change root into the new root filesystem to complete the second stage of debootstrap.

sudo chroot ./ubuntu-armhf-rootfs

6. Complete Debootstrap Second Stage

Inside the chroot environment, run the second stage of debootstrap.

/debootstrap/debootstrap --second-stage

7. Configure the Rootfs

Now configure the basic settings of your new root filesystem.

- Set the hostname:

echo "ubuntu-armhf" > /etc/hostname

- Set up the hosts file:

cat <<EOL > /etc/hosts
127.0.0.1   localhost
127.0.1.1   ubuntu-armhf
EOL

- Create fstab:

cat <<EOL > /etc/fstab
proc            /proc           proc    defaults        0       0
sysfs           /sys            sysfs   defaults        0       0
devpts          /dev/pts        devpts  gid=5,mode=620  0       0
tmpfs           /run            tmpfs   defaults        0       0
tmpfs           /run/lock       tmpfs   nodev,nosuid,noexec 0   0
EOL

- Set up networking:

cat <<EOL > /etc/network/interfaces
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp
EOL

- Set the root password:

passwd

- Create a user:

adduser ubuntu
usermod -aG sudo ubuntu

- Install essential packages:

apt update
apt install sudo nano ssh net-tools network-manager usbutils

8. Exit the Chroot

Exit the chroot environment.

exit

9. Clean Up

Remove the qemu-arm-static binary from the rootfs.

sudo rm ./ubuntu-armhf-rootfs/usr/bin/qemu-arm-static