diff -Nru bilibop-0.5.5/debian/changelog bilibop-0.5.6/debian/changelog
--- bilibop-0.5.5/debian/changelog	2019-01-30 23:52:22.000000000 +0000
+++ bilibop-0.5.6/debian/changelog	2019-05-11 01:40:04.000000000 +0000
@@ -1,3 +1,15 @@
+bilibop (0.5.6) unstable; urgency=high
+
+  * bilibop-lockfs:
+    - fix boot failure by supporting the new path /usr/bin/mount as well as
+      the legacy /bin/mount (kept for backward compatibility).
+      Closes: #928658.
+    - fix boot failure about mounts flagged 'ro' in fstab by applying the
+      'ro' option to the union instead of its writable branch.
+      Closes: #928780.
+
+ -- Yann Amar <quidame@poivron.org>  Sat, 11 May 2019 01:40:04 +0000
+
 bilibop (0.5.5) unstable; urgency=low
 
   * debian/control:
diff -Nru bilibop-0.5.5/lib/bilibop/lockfs_mount_helper bilibop-0.5.6/lib/bilibop/lockfs_mount_helper
--- bilibop-0.5.5/lib/bilibop/lockfs_mount_helper	2017-09-11 18:52:36.000000000 +0000
+++ bilibop-0.5.6/lib/bilibop/lockfs_mount_helper	2019-05-11 01:40:04.000000000 +0000
@@ -54,11 +54,17 @@
 }
 # ===========================================================================}}}
 
-# Works only if the parent process is /bin/mount:
-if [ "$(readlink -f /proc/${PPID}/exe)" != "/bin/mount" ]; then
-    usage >&2
-    exit 3
-fi
+# Works only if the parent process is the mount command (/bin/mount for backward
+# compatibility, or /usr/bin/mount). This will ensure arguments are passed in a
+# specific order, and shorten the code to parse them.
+case "$(readlink -f /proc/${PPID}/exe)" in
+    "/bin/mount"|"/usr/bin/mount")
+        ;;
+    *)
+        usage >&2
+        exit 3
+        ;;
+esac
 
 . /lib/bilibop/common.sh
 get_bilibop_variables
@@ -182,31 +188,32 @@
 mntpnt="${2}"
 options="${4}"
 
-# Parse mount options. Two cases:
+# Parse mount options and allocate them to the proper branches or their
+# union:
 # 1. the block device will be mounted with the same options than in the
 #    original fstab entry, plus 'ro'.
 # 2. the tmpfs will be mounted with only some options of the previous:
-#    ro, nodev, noexec, nosuid, if they exist.
+#    nodev, noexec, nosuid, if they exist.
+# 3. when set in the persistent fstab, the ro flag could be deferred to
+#    the tmpfs mount (and the union will inherit of it), but this would
+#    forbid creation of subdirectories for submountpoints.
 
 for opt in $(IFS=','; echo ${options}); do
-    # 1. Options for the readonly branch:
     case "${opt}" in
         fstype=*)
             eval "${opt}"
             ;;
         rw)
             ;;
-        *)
-            robr_opts="${robr_opts:+${robr_opts},}${opt}"
+        ro)
+            union_opts="${union_opts:+${union_opts},}${opt}"
             ;;
-    esac
-
-    # 2. Options for the writable branch:
-    case "${opt}" in
-        ro|nodev|noexec|nosuid)
+        nodev|noexec|nosuid)
             rwbr_opts="${rwbr_opts:+${rwbr_opts},}${opt}"
+            robr_opts="${robr_opts:+${robr_opts},}${opt}"
             ;;
         *)
+            robr_opts="${robr_opts:+${robr_opts},}${opt}"
             ;;
     esac
 done
@@ -374,9 +381,9 @@
 
 # Now set the union filesystem mount options
 if [ "${METHOD}" = "aufs" ]; then
-    UNIONFS_OPTS="br:${rwbr}=rw:${robr}=${RO}"
+    UNIONFS_OPTS="${union_opts:+${union_opts},}br:${rwbr}=rw:${robr}=${RO}"
 elif [ "${METHOD}" = "overlay" ]; then
-    UNIONFS_OPTS="lowerdir=${robr},upperdir=${rwbr},workdir=${work}"
+    UNIONFS_OPTS="${union_opts:+${union_opts},}lowerdir=${robr},upperdir=${rwbr},workdir=${work}"
 fi
 
 # Try to mount the union fs now. In case of failure, undo what has been done
diff -Nru bilibop-0.5.5/lib/bilibop/lockfs.sh bilibop-0.5.6/lib/bilibop/lockfs.sh
--- bilibop-0.5.5/lib/bilibop/lockfs.sh	2017-09-11 18:52:36.000000000 +0000
+++ bilibop-0.5.6/lib/bilibop/lockfs.sh	2019-05-11 01:40:04.000000000 +0000
@@ -319,6 +319,7 @@
 #!/bin/sh
 # THIS IS A FALLBACK; IT DON'T LOCK FS BUT JUST RECALLS /bin/mount WITH VALID FSTYPE AND OPTIONS.
 PATH="/bin"
+[ "\$(readlink -f /proc/\${PPID}/exe)" = "/usr/bin/mount" ] ||
 [ "\$(readlink -f /proc/\${PPID}/exe)" = "/bin/mount" ] || exit 3
 for opt in \$(IFS=',' ; echo \${4}) ; do
     case "\${opt}" in