fully automatic sd card partitioning and formatting

3 files changed, 99 insertions, 48 deletions

diff --git a/makefile b/makefile
index da94b65..a211676 100644
--- a/makefile
+++ b/makefile
@@ -18,7 +18,8 @@ CTRIZE += --env-file ./env
 CTRIZE += $(CTR_IMG_TAG)
 export
 
-# create files that represent otherwise PHONY targets
+# create dummy files to represent non-file targets (container image build
+# status, sd card partition status, git submodule initialization, etc.)
 $(shell state/gen)
 -include state/auto.mk
 
@@ -26,8 +27,12 @@ $(shell state/gen)
 include ./env
 export
 
+# shortcuts
 .PHONY: all
 all: $(BOOTLOADER_FILES)
+.PHONY: sd_format sd_partition
+sd_format: state/sdcard_fmt
+sd_partition: state/sdcard_part
 
 state/container_img: Containerfile
 	$(CTR) build --tag $(CTR_IMG_TAG) .
@@ -38,6 +43,15 @@ state/submodules:
 	$(GIT) submodule update
 	touch $@
 
+state/sdcard_part:
+	$(AS_ROOT) util/part $(SDCARD_DISK)
+	touch $@
+
+state/sdcard_fmt: state/sdcard_part
+	$(AS_ROOT) mkfs.vfat -n BOOT -F 32 $(SDCARD_PART_BOOT)
+	$(AS_ROOT) mkfs.ext4 -L ROOTFS -F $(SDCARD_PART_ROOTFS)
+	touch $@
+
 BOOTLOADER_FILES += bootloader/MLO
 BOOTLOADER_FILES += bootloader/u-boot.img
 BOOTLOADER_FILES += bootloader/u-boot.dtb
@@ -59,8 +73,9 @@ load_bootloader: $(BOOTLOADER_FILES)
 	$(AS_ROOT) $(CP) $(BOOTLOADER_FILES) mnt/boot
 	$(UMOUNT) mnt/boot
 
-.PHONY: sd_format
-sd_format:
-	$(AS_ROOT) mkfs.vfat -n BOOT -F 32 $(SDCARD_PART_BOOT)
-	$(AS_ROOT) mkfs.ext4 -L ROOTFS -F $(SDCARD_PART_ROOTFS)
+.PHONY: status
+status:
+	@echo '### STATUS REPORT'
+	@echo '# DETECTED SD CARD'
+	@cat state/auto.mk
 
diff --git a/state/gen b/state/gen
index 23a3382..6066685 100755
--- a/state/gen
+++ b/state/gen
@@ -4,9 +4,17 @@ exec 1>&2
 # create files in the same directory as this script
 cd "$(dirname "$0")"
 # do not run anything if make was run with -n (dry run)
-# [ "${MAKEFLAGS#*n}" != "$MAKEFLAGS" ] && exit
+[ "${MAKEFLAGS#*n}" != "$MAKEFLAGS" ] && exit
 
-touch_rm_exit_code() { [ $? -eq 0 ] && touch "$1" || rm -f "$1" ; }
+touch_rm_exit_code() {
+	PREV_EC="$?"
+	if [ "$PREV_EC" -eq 0 ] ; then
+		! [ -e "$1" ] && touch "$1"
+	else
+		rm -f "$1"
+	fi
+	return "$PREV_EC"
+}
 
 # container image (initialized here, updated in makefile)
 $CTR image exists "$CTR_IMG_TAG" 1> /dev/null 2> /dev/null
@@ -16,50 +24,53 @@ touch_rm_exit_code container_img
 test -z "$(git submodule status | grep '^-')"
 touch_rm_exit_code submodules
 
-rm -f auto.mk
+rm -f sdcard_part sdcard_fmt
+# if no explicit SDCARD_DISK is set, guess which device is the sd card by
+# checking if it is removable AND has a size of approx. 8GB
+if [ -z "$SDCARD_DISK" ] ; then
+	SDCARD_DISK="$(lsblk --noheadings --bytes --output PATH,SIZE,TYPE,RM | awk '
+		$3 != "disk" { next }
+		$2 < 7900000000 { next }
+		$2 > 8000000000 { next }
+		$4 != 1 { next }
+		{ print $1 }' | head -n1)"
+fi
+if [ -n "$SDCARD_DISK" ] ; then
+	# check if the sd card is partitioned correctly if no partition path
+	# variables are set
+	if [ -z "$SDCARD_PART_BOOT" ] || [ -z "$SDCARD_PART_ROOTFS" ] ; then
+		PARTS="$(lsblk "$SDCARD_DISK" --bytes --noheadings \
+			--output PATH,SIZE,TYPE,PTTYPE,FSTYPE,LABEL,PARTFLAGS)"
 
-# guess which device is the sd card by size (around 8GB)
-for SDCARD_DISK in "$(lsblk --noheadings --bytes --output PATH,SIZE,TYPE | awk '
-	$3 != "disk" { next }
-	($2 < 7900000000) { next }
-	($2 > 8000000000) { next }
-	{ print $1 }')"
-do
-	[ -z "$SDCARD_DISK" ] && continue
-	# check if the sd card is already correctly partitioned & formatted
-	PARTS="$(lsblk "$SDCARD_DISK" --noheadings --output PATH,SIZE,TYPE,PTTYPE,FSTYPE,LABEL | awk '
-		NR == 1 {
-			if ($4 != "dos") exit(1)
-		}
-		NR == 2 {
-			if ($6 != "BOOT") exit(1)
-			if ($2 != "64M") exit(1)
-			if ($5 != "vfat") exit(1)
-			print $1
-		}
-		NR == 3 {
-			if ($6 != "ROOTFS") exit(1)
-			if ($5 != "ext4") exit(1)
-			print $1
-		}
-		END { if (NR != 3) exit(1) }')" || continue
-	SDCARD_PART_BOOT="$(echo "$PARTS" | sed '1!d')"
-	SDCARD_PART_ROOTFS="$(echo "$PARTS" | sed '2!d')"
-	break
-done
+		# check if the disk is partitioned correctly
+		echo "$PARTS" | awk '
+			$3 == "part" { parts += 1 }
+			NR == 1 { if ($4 != "dos") exit(1) }
+			NR == 2 { if ($2 != 64 * 2^20) exit(1) }
+			END { if (parts != 2) exit(1) }' && touch sdcard_part
 
-if [ -n "$SDCARD_DISK" ]; then
-	echo "SDCARD_DISK ?= $SDCARD_DISK" >> auto.mk
-fi
+		if [ $? -eq 0 ] ; then
+			SDCARD_PART_BOOT="$(echo "$PARTS" | awk 'NR == 2 { print $1 }')"
+			SDCARD_PART_ROOTFS="$(echo "$PARTS" | awk 'NR == 3 { print $1 }')"
 
-if [ -n "$SDCARD_PART_BOOT" ] && [ -n "$SDCARD_PART_ROOTFS" ]; then
-	echo "SDCARD_PART_BOOT ?= $SDCARD_PART_BOOT" >> auto.mk
-	echo "SDCARD_PART_ROOTFS ?= $SDCARD_PART_ROOTFS" >> auto.mk
-	touch sdcard_part_fmt
-else
-	rm -f sdcard_part_fmt
+			# check if the disk is formatted correctly
+			echo "$PARTS" | awk '
+				NR == 2 {
+					if ($5 != "vfat") exit(1)
+					if ($6 != "BOOT") exit(1)
+					if ($7 != "0x80") exit(1)
+				}
+				NR == 3 {
+					if ($5 != "ext4") exit(1)
+					if ($6 != "ROOTFS") exit(1)
+				}' && touch sdcard_fmt
+		fi
+	fi
 fi
 
-# export all variables in auto.mk
-echo "export" >> auto.mk
+cat << EOF > auto.mk
+SDCARD_DISK ?= $SDCARD_DISK
+SDCARD_PART_BOOT ?= $SDCARD_PART_BOOT
+SDCARD_PART_ROOTFS ?= $SDCARD_PART_ROOTFS
+EOF
 
diff --git a/util/part b/util/part
new file mode 100755
index 0000000..cf9abe5
--- /dev/null
+++ b/util/part
@@ -0,0 +1,25 @@
+#!/bin/sh
+SDCARD_DISK="$1"
+if ! [ -n "$SDCARD_DISK" ] ; then
+	cat << EOF >&2
+ERROR: could not automatically detect an SD card. Please insert an SD card of
+approx. 8GB, or manually set SDCARD_DISK in ./makefile
+EOF
+	exit 1
+fi
+if ! [ -w "$SDCARD_DISK" ] ; then
+	echo "ERROR: cannot not write to $SDCARD_DISK. Are you root?" >&2
+	exit 1
+fi
+if ! [ -b "$SDCARD_DISK" ] ; then
+	echo "ERROR: $SDCARD_DISK does not appear to be a block device" >&2
+	exit 1
+fi
+
+set -e
+
+sfdisk "$SDCARD_DISK" << 'EOF'
+label: dos
+,64M,0C,*
+,+  ,83,
+EOF