creting-alpine-rpi-image

gistfile1.txt

#!/usr/bin/env bash

set -euxo pipefail

umount /tmp/mnt || true
losetup --detach /dev/loop0 || true
rm -rf root.img || true

# create an empty image
dd if=/dev/zero of=root.img seek=256M bs=1 count=0

{
    echo o      # Create a new empty DOS partition table

    # set up partition 1
    echo n      # Add a new partition
    echo p      # Primary partition
    echo 1      # Partition 1
    echo        # use default for first sector
    echo +64M   # Last sector
    echo t      # set partition type
    echo c      # set partition type to W95 FAT32 (LBA)
    echo a      # set partition 1 as bootable/active

    # now we create partition 2
    echo n      # new partition
    echo p      # primary partition
    echo 2      # partion number 2
    echo        # default, start immediately after preceding partition
    echo        # default, extend partition to end of disk

    # print the in-memory partition table
    echo p

    # save and quit
    echo w
    echo q
} | fdisk root.img

losetup --show -P /dev/loop0 root.img
mkfs.vfat /dev/loop0p1
mkfs.ext4 /dev/loop0p2
losetup --detach /dev/loop0

mkdir -p /tmp/mnt

startSector="$(sfdisk -J ./root.img | jq '.partitiontable.partitions[] | select(.type == "c") | .start')"
offset="$(( $startSector * 512 ))"
mount -t vfat -o loop -o "offset=$offset" root.img /tmp/mnt

curl -fsSL http://dl-cdn.alpinelinux.org/alpine/v3.9/releases/aarch64/alpine-rpi-3.9.4-aarch64.tar.gz -o- | tar -xzv --no-same-owner -C /tmp/mnt --file -

umount /tmp/mnt