TAILORED: build 4k sector sized templates only

https://github.com/QubesOS/qubes-issues/issues/4974#issuecomment-575955927

mount_root.sh

@@ -18,7 +18,7 @@ mkdir -p mnt
 
 MNTDIR=$(pwd)/mnt
 
-LOOP=$(/sbin/losetup -f --show -o $OFFSET $ROOTIMG)
+LOOP=$(/sbin/losetup -b 4096 -f --show -o $OFFSET $ROOTIMG)
 
 if [ x$LOOP = x ] ; then
 echo "Cannot setup loopback device for the $ROOTIMG file -- perhaps a permissions problem?"

prepare_image

@@ -50,10 +50,13 @@ echo "-> Preparing instalation of ${DIST} template..."
 if [ -f "${IMG}" ]; then
     echo "-> Image file already exists, assuming *update*..."
     if [ "0$TEMPLATE_ROOT_WITH_PARTITIONS" -eq 1 ]; then
-        IMG_LOOP=$(/sbin/losetup -P -f --show "$IMG")
+        IMG_LOOP=$(/sbin/losetup -b 4096 -P -f --show "$IMG")
+        # BUG: losetup's partscan (-P) does nothing when trying 4096 sectors formatted images on a 512 sectors backing device.
+        #      Hence it needs an additional partprobe run.
+        /sbin/partprobe $IMG_LOOP
         IMG_DEV=${IMG_LOOP}p3
     else
-        IMG_LOOP=$(/sbin/losetup -f --show "$IMG")
+        IMG_LOOP=$(/sbin/losetup -b 4096 -f --show "$IMG")
         IMG_DEV=${IMG_LOOP}
     fi
 else
@@ -62,8 +65,12 @@ else
 
     if [ "0$TEMPLATE_ROOT_WITH_PARTITIONS" -eq 1 ]; then
         echo "-> Creating partition table"
-        # have static UUIDs to make partition table reproducible
-        sfdisk "$IMG" <<EOF || exit 1
+        IMG_LOOP=$(/sbin/losetup -b 4096 -P -f --show "$IMG")
+        # When a 4096 sectors formatted image gets created with the sfdisk, the partitions are automatically visible
+        # to the system. Hence no need to run additional partprobe.
+
+        # Have static UUIDs to make partition table reproducible
+        sfdisk "$IMG_LOOP" <<EOF || exit 1
 label: gpt
 label-id: f4796a2a-e377-45bd-b539-d6d49e569055
 
@@ -72,17 +79,21 @@ size=2MiB, type=21686148-6449-6E6F-744E-656564454649, uuid=1e6c9db4-1e91-46c4-84
 type=0FC63DAF-8483-4772-8E79-3D69D8477DE4, uuid=693244e6-3e07-47bf-ad79-acade4293fe7, name="Root filesystem"
 EOF
 
-        IMG_LOOP=$(/sbin/losetup -P -f --show "$IMG")
         IMG_DEV=${IMG_LOOP}p3
     else
-        IMG_LOOP=$(/sbin/losetup -f --show "$IMG")
+        IMG_LOOP=$(/sbin/losetup -b 4096 -f --show "$IMG")
         IMG_DEV=${IMG_LOOP}
     fi
 
+    # make sure the IMG_DEV is present
+    c=0; while [ ! -b $IMG_DEV ]; do sleep 1; c=$((c+1)); [ $c -ge 5 ] && break; done; unset c
+
     echo "-> Creating filesystem..."
     /sbin/mkfs.ext4 -q -F "${IMG_DEV}" || exit 1
 fi
 
+# make sure the IMG_DEV is present
+c=0; while [ ! -b $IMG_DEV ]; do sleep 1; c=$((c+1)); [ $c -ge 5 ] && break; done; unset c
 mount "${IMG_DEV}" "${INSTALLDIR}" || exit 1
 trap "umount_kill $(readlink -m ${INSTALLDIR})" EXIT
 "${SCRIPTSDIR}/01_install_core.sh"

qubeize_image

@@ -72,12 +72,17 @@ fi
 echo "--> Mounting $IMG"
 mkdir -p mnt
 if [ "0$TEMPLATE_ROOT_WITH_PARTITIONS" -eq 1 ]; then
-    IMG_LOOP=$(/sbin/losetup -P -f --show "$IMG")
+    IMG_LOOP=$(/sbin/losetup -b 4096 -P -f --show "$IMG")
+    # BUG: losetup's partscan (-P) does nothing when trying 4096 sectors formatted images on a 512 sectors backing device.
+    #      Hence it needs an additional partprobe run.
+    /sbin/partprobe $IMG_LOOP
     IMG_DEV=${IMG_LOOP}p3
 else
-    IMG_LOOP=$(/sbin/losetup -f --show "$IMG")
+    IMG_LOOP=$(/sbin/losetup -b 4096 -f --show "$IMG")
     IMG_DEV=${IMG_LOOP}
 fi
+# make sure the IMG_DEV is present
+c=0; while [ ! -b $IMG_DEV ]; do sleep 1; c=$((c+1)); [ $c -ge 5 ] && break; done; unset c
 mount "$IMG_DEV" mnt || exit 1
 export INSTALLDIR=mnt