diff --git a/diskimage_builder/lib/disk-image-create b/diskimage_builder/lib/disk-image-create
index 8400ae70..89aa8818 100644
--- a/diskimage_builder/lib/disk-image-create
+++ b/diskimage_builder/lib/disk-image-create
@@ -345,6 +345,7 @@ run_d_in_target pre-install
 run_d_in_target install
 do_extra_package_install
 run_d_in_target post-install
+run_d post-root
 # ensure we do not have a lost+found directory in the root folder
 # that could cause copy to fail (it will be created again later
 # when creating the file system, if it needs such directory)
diff --git a/doc/source/developer/developing_elements.rst b/doc/source/developer/developing_elements.rst
index d37bc09c..342bbb72 100644
--- a/doc/source/developer/developing_elements.rst
+++ b/doc/source/developer/developing_elements.rst
@@ -69,7 +69,9 @@ The phases are:
 #. ``pre-install.d``
 #. ``install.d``
 #. ``post-install.d``
+#. ``post-root.d``
 #. ``block-device.d``
+#. ``pre-finalise.d``
 #. ``finalise.d``
 #. ``cleanup.d``
 
@@ -124,6 +126,13 @@ The phases are:
 
   * runs: **in chroot**
 
+``post-root.d``
+  Run code outside the chroot. This is a good place to perform tasks that
+  cannot run inside the chroot and must run after installing things. The
+  root filesystem content is rooted at ``$TMP_BUILD_DIR/mnt``.
+
+  * runs: **outside chroot**
+
 ``block-device.d``
   Customise the block device that the image will be made on (for example to
   make partitions). Runs after the target tree has been fully populated but
diff --git a/releasenotes/notes/post-root-stage-51da051bcdfbc55f.yaml b/releasenotes/notes/post-root-stage-51da051bcdfbc55f.yaml
new file mode 100644
index 00000000..c4f8b3d8
--- /dev/null
+++ b/releasenotes/notes/post-root-stage-51da051bcdfbc55f.yaml
@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    A ``post-root`` stage is added that runs outside the chroot and
+    before the image size calculation.  For example, this may be useful
+    for running things that copy much data into the image and need to be
+    outside of the chroot and after install stages which run inside the chroot.