add first version of 01_create_sdcard.sh

helper to rebuild sdcard in reproducible steps
add .gitignore for cache step folder

build_arm_image/.gitignore

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+_build_arm_steps

build_arm_image/01_create_sdcard.sh

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+#!/bin/bash 
+#
+# Create the sdcard on your PC with the latest debian.
+#
+# Usage:
+#  ./01_create_sdcard.sh downloaded_debian_image.zip /dev/sdcard_device
+#
+# Licence: GPLv3
+# Author: sylvain303@github
+
+# informations about Raspbian image:
+# Raspbian Jessie Lite Version: November 2015 Release date: 2015-11-21
+# version: SHA-1 of the .zip: 97888fcd9bfbbae2a359b0f1d199850852bf0104
+# Kernel version: 4.1
+# http://downloads.raspberrypi.org/raspbian/release_notes.txt
+
+DOWNLOAD_URL=https://www.raspberrypi.org/downloads/raspbian/
+SHA_DEBIAN_IMG_ZIP=97888fcd9bfbbae2a359b0f1d199850852bf0104
+
+die() {
+    echo "$*"
+    exit 1
+}
+
+# helper, test if a shell program exists in PATH
+test_tool() {
+    local cmd=$1
+    if type $cmd > /dev/null
+    then
+        # OK
+        return 0
+    else
+        die "tool missing: $cmd"
+    fi
+}
+
+# skip if the file exists.
+# usage: skip_if _build_arm_steps/somefile && return 2
+skip_if() {
+    if [[ -e "$1" ]]
+    then
+        echo "cached"
+        return 0
+    fi
+   # echo -n "continue for $1"
+    return 1
+}
+
+
+sha_verify_zip() {
+    local zip=$DEBIAN_IMG_ZIP
+    local out=_build_arm_steps/sha_verify_zip
+    skip_if $out && return 2
+    sha1sum $zip > $out
+    # read only sha check hash
+    local sha="$(sed -e 's/\(^[a-f0-9]\+\).*/\1/' $out)"
+    if [[ "$sha" != "$SHA_DEBIAN_IMG_ZIP" ]]
+    then
+        echo "NOK: '$sha' != '$SHA_DEBIAN_IMG_ZIP'"
+        exit 1
+    fi
+}
+
+# unzip raspbian image in the cache folder
+unzip_img() {
+    if ! skip_if _build_arm_steps/*.img
+    then
+        unzip -o $DEBIAN_IMG_ZIP -d _build_arm_steps
+    fi
+    # get extrated image filename from zip file
+    DEBIAN_IMG=$(ls _build_arm_steps/ | grep \\.img$)
+}
+
+# helper try to guess top device name
+# /dev/sdp2 => /dev/sdp
+# /dev/mmcblk0p1 => /dev/mmcblk0
+# just some regexp no smart thing
+get_top_device() {
+    local device="$1"
+    local regexp1='^/dev/sd[a-z]'
+    local regexp2='^/dev/mmcblk[0-9]'
+
+    if [[ "$device" =~ $regexp1 ]]
+    then
+        #echo sd
+        device="${device/[0-9]/}"
+    elif [[ "$device" =~ $regexp2 ]]
+    then
+        #echo mmcblk
+        device="${device/p[0-9]/}"
+    fi
+
+    echo "$device"
+}
+
+umount_all_partition() {
+    local p
+    # search and replace all occurence of / by .
+    local pattern=${SDCARD////.}
+    pattern=${pattern/p[0-9]/}
+    for p in $(df | awk "/^$pattern/ { print \$1 }")
+    do
+        echo sudo umount $p
+    done
+    echo "done device for sdcard=${pattern//.//}"
+}
+
+dd_to_sdcard() {
+    # ensure
+    echo dd bs=16M if=_build_arm_steps/$DEBIAN_IMG of=$SDCARD
+}
+
+test_all_tools() {
+    for t in $*
+    do
+        test_tool $t
+    done
+}
+
+# functions call in that order, edit remove a long running step if already done or if
+# you want to skip it, step states are saved in folder _build_arm_steps and skipped automatically.
+STEPS="
+sha_verify_zip 
+unzip_img
+umount_all_partition
+dd_to_sdcard"
+
+# main wrapper, so the script can be sourced for debuging purpose or unittesting
+main() {
+    # positional argument must be script argument.
+    # init
+    if [[ -z "$1" ]]
+    then
+        echo "argument 1 error: expecting raspbian image file.zip"
+        echo "can be downloaded here: $DOWNLOAD_URL"
+        exit 1
+    fi
+
+    # reading script argument
+    DEBIAN_IMG_ZIP=$1
+    [[ -f "$DEBIAN_IMG_ZIP" ]] || die "error raspbian image not found: '$DEBIAN_IMG_ZIP'"
+    SDCARD=$(get_top_device "$2")
+    [[ -z "$SDCARD" ]] && die "argument 2 error: expecting sdcard_device"
+
+    test_all_tools dd sync sudo
+    mkdir -p _build_arm_steps
+
+    # actions loop
+    for s in $STEPS
+    do
+        echo -n "$s: "
+        eval $s
+    done
+}
+
+# sourcing code detection, if code is sourced for debug purpose, main is not executed.
+[[ $0 != "$BASH_SOURCE" ]] && sourced=1 || sourced=0
+if  [[ $sourced -eq 0 ]]
+then
+    # pass positional argument as is
+    main "$@"
+fi