[OpenWrt-Devel] [PATCH][RFC] x86: Save and restore partition table during upgrade

[Rob Mosher]

This patch will save the partition table before an upgrade.
If the installed image has not changed the partition structure
the saved table will be restored, ensuring any user created
partitions will be present after the upgrade.

An option is added to sysupgrade to disable this feature.

Signed-off-by: Rob Mosher <nyt-openwrt at countercultured.net>
---
 package/base-files/files/lib/upgrade/common.sh     |  1 +
 package/base-files/files/sbin/sysupgrade           |  3 ++
 target/linux/x86/Makefile                          |  2 +
 .../linux/x86/base-files/lib/upgrade/platform.sh   | 45 ++++++++++++++++++++++
 4 files changed, 51 insertions(+)

diff --git a/package/base-files/files/lib/upgrade/common.sh b/package/base-files/files/lib/upgrade/common.sh
index 761b4c1..aed7f8e 100644
--- a/package/base-files/files/lib/upgrade/common.sh
+++ b/package/base-files/files/lib/upgrade/common.sh
@@ -67,6 +67,7 @@ run_ramfs() { # <command> [...]
 	install_bin /usr/sbin/ubirsvol
 	install_bin /usr/sbin/ubirmvol
 	install_bin /usr/sbin/ubimkvol
+	install_bin /usr/sbin/sfdisk
 	for file in $RAMFS_COPY_BIN; do
 		install_bin ${file//:/ }
 	done
diff --git a/package/base-files/files/sbin/sysupgrade b/package/base-files/files/sbin/sysupgrade
index 93f0749..2f441f8 100755
--- a/package/base-files/files/sbin/sysupgrade
+++ b/package/base-files/files/sbin/sysupgrade
@@ -10,6 +10,7 @@ export INTERACTIVE=0
 export VERBOSE=1
 export SAVE_CONFIG=1
 export SAVE_OVERLAY=0
+export SAVE_PARTITIONS=1
 export DELAY=
 export CONF_IMAGE=
 export CONF_BACKUP_LIST=0
@@ -29,6 +30,7 @@ while [ -n "$1" ]; do
 		-q) export VERBOSE="$(($VERBOSE - 1))";;
 		-n) export SAVE_CONFIG=0;;
 		-c) export SAVE_OVERLAY=1;;
+		-p) export SAVE_PARTITIONS=0;;
 		-b|--create-backup) export CONF_BACKUP="$2" NEED_IMAGE=1; shift;;
 		-r|--restore-backup) export CONF_RESTORE="$2" NEED_IMAGE=1; shift;;
 		-l|--list-backup) export CONF_BACKUP_LIST=1; break;;
@@ -62,6 +64,7 @@ upgrade-option:
 	-i           interactive mode
 	-c           attempt to preserve all changed files in /etc/
 	-n           do not save configuration over reflash
+	-p           do not attempt to restore the partition table after flash.
 	-T | --test
 	             Verify image and config .tar.gz but do not actually flash.
 	-F | --force
diff --git a/target/linux/x86/Makefile b/target/linux/x86/Makefile
index e4bc0d9..e5b4378 100644
--- a/target/linux/x86/Makefile
+++ b/target/linux/x86/Makefile
@@ -13,6 +13,8 @@ FEATURES:=squashfs ext4 vdi vmdk pcmcia targz
 SUBTARGETS=generic xen_domu ep80579 geode kvm_guest 64
 MAINTAINER:=Felix Fietkau <nbd at openwrt.org>
 
+DEFAULT_PACKAGES += sfdisk
+
 KERNEL_PATCHVER:=4.4
 
 KERNELNAME:=bzImage
diff --git a/target/linux/x86/base-files/lib/upgrade/platform.sh b/target/linux/x86/base-files/lib/upgrade/platform.sh
index 73ab5ef..7f5a2b1 100644
--- a/target/linux/x86/base-files/lib/upgrade/platform.sh
+++ b/target/linux/x86/base-files/lib/upgrade/platform.sh
@@ -55,12 +55,57 @@ platform_copy_config() {
 	fi
 }
 
+save_bootparts() {
+	disk=${BOOTPART%[0-9]}
+	if [ -b $disk ]; then
+		echo "Backing up partition table..."
+		sfdisk -d $disk > /tmp/sfdisk.before
+		grep size= /tmp/sfdisk.before | grep -E -v 'size=\s+0,' > /tmp/sfdisk.before.nonempty
+	fi
+}
+
+restore_bootparts() {
+	disk=${BOOTPART%[0-9]}
+	if [ -b $disk ]; then
+		sfdisk -d $disk > /tmp/sfdisk.after
+		grep size= /tmp/sfdisk.after | grep -E -v 'size=\s+0,' > /tmp/sfdisk.after.nonempty
+		before=$(cat /tmp/sfdisk.before.nonempty)
+		after=$(cat /tmp/sfdisk.after.nonempty)
+
+		#ensure we have both partition tables
+		if [ -z "$before" -o -z "$after" ]; then
+			echo "Could not read partition table"
+			return 1
+		fi
+		
+		#if nothing changed, we do not need to restore
+		if [ "$before" = "$after" ]; then
+			echo "Parition layout unchanged"
+			return 0
+		fi
+
+		diff=$(grep -F -x -v -f /tmp/sfdisk.before.nonempty /tmp/sfdisk.after.nonempty)
+
+		#if partition layout changed, do not restore
+		if [ -n "$diff" ]; then
+			echo "Partition layout changed, not restoring."
+			return 1
+		fi
+
+		echo "Restoring partition table..."
+		sfdisk $disk --force < /tmp/sfdisk.before >&/dev/null
+	fi
+}
+
 platform_do_upgrade() {
 	platform_export_bootpart
 
 	if [ -b "${BOOTPART%[0-9]}" ]; then
 		sync
+		[ $SAVE_PARTITIONS = "1" ] && save_bootparts
 		get_image "$@" | dd of="${BOOTPART%[0-9]}" bs=4096 conv=fsync
 		sleep 1
+		[ $SAVE_PARTITIONS = "1" ] && restore_bootparts
 	fi
 }
+
-- 
2.1.4
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