1 files changed, 57 insertions, 0 deletions
diff --git a/debian/udev.preinst b/debian/udev.preinst
new file mode 100644
index 0000000..96a4c5e
--- /dev/null
+++ b/debian/udev.preinst
@@ -0,0 +1,57 @@
+#!/bin/sh
+
+set -e
+
+is_merged() {
+  local directories="/bin /sbin /lib"
+  for dir in $directories; do
+    [ -e "$DPKG_ROOT$dir" ] || continue
+    [ "$(readlink -f "$DPKG_ROOT$dir")" = "$DPKG_ROOT/usr$dir" ] || return 1
+  done
+
+  # Avoid an exact match, as the target might vary depending on the tool
+  # building the image. For example, systemd-nspawn links /lib64 to
+  # /usr/lib/aarch64-linux-gnu on arm64, while on amd64 debootstrap links it to
+  # /usr/lib64 and doesn't create it at all on arm64.
+  # See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1019575
+  local arch_directories="/lib64 /lib32 /libo32 /libx32"
+  for dir in $arch_directories; do
+    [ -e "$DPKG_ROOT$dir" ] || continue
+    case "$(readlink -f "$DPKG_ROOT$dir")" in
+        "$DPKG_ROOT/usr/lib"*) ;;
+        *) return 1;;
+    esac
+  done
+
+  return 0
+}
+
+fail_if_unmerged() {
+  if is_merged; then return; fi
+
+  cat << END
+
+
+******************************************************************************
+*
+* The udev package cannot be installed because this system does
+* not have a merged /usr.
+*
+* Please install the usrmerge package to convert this system to merged-/usr.
+*
+* For more information please read https://wiki.debian.org/UsrMerge.
+*
+******************************************************************************
+
+
+END
+  exit 1
+}
+
+case "$1" in
+    install|upgrade)
+    fail_if_unmerged
+    ;;
+esac
+
+#DEBHELPER#