diff --git a/meta/classes/rootfsdebugfiles.bbclass b/meta/classes/rootfsdebugfiles.bbclass
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+# This class installs additional files found on the build host
+# directly into the rootfs.
+#
+# One use case is to install a constant ssh host key in
+# an image that gets created for just one machine. This
+# solves two issues:
+# - host key generation on the device can stall when the
+#   kernel has not gathered enough entropy yet (seen in practice
+#   under qemu)
+# - ssh complains by default when the host key changes
+#
+# For dropbear, with the ssh host key store along side the local.conf:
+# 1. Extend local.conf:
+#    INHERIT += "rootfsdebugfiles"
+#    ROOTFS_DEBUG_FILES += "${TOPDIR}/conf/dropbear_rsa_host_key ${IMAGE_ROOTFS}/etc/dropbear/dropbear_rsa_host_key ;"
+# 2. Boot the image once, copy the dropbear_rsa_host_key from
+#    the device into your build conf directory.
+#
+# Do not use for production images! It bypasses several
+# core build mechanisms (updating the image when one
+# of the files changes, license tracking in the image
+# manifest, ...).
+
+ROOTFS_DEBUG_FILES ?= ""
+ROOTFS_DEBUG_FILES[doc] = "Lists additional files or directories to be installed with 'cp -a' in the format 'source1 target1;source2 target2;...'"
+
+ROOTFS_POSTPROCESS_COMMAND += "rootfs_debug_files ;"
+rootfs_debug_files () {
+   #!/bin/sh -e
+   echo "${ROOTFS_DEBUG_FILES}" | sed -e 's/;/\n/g' | while read source target; do
+      if [ -e "$source" ]; then
+         mkdir -p $(dirname $target)
+         cp -a $source $target
+      fi
+   done
+}