diff --git a/docs/topic/index.md b/docs/topic/index.md
index 90e7e9c..dc38061 100644
--- a/docs/topic/index.md
+++ b/docs/topic/index.md
@@ -12,6 +12,7 @@ three-environments
 security
 customizing-installer
 installer-actions
+installer-upgrade-actions
 tljh-config
 authenticator-configuration
 escape-hatch
diff --git a/docs/topic/installer-upgrade-actions.md b/docs/topic/installer-upgrade-actions.md
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@@ -0,0 +1,30 @@
+(topic-installer-upgrade-actions)=
+
+# What is done during an upgrade of TLJH?
+
+Once TLJH has been installed, it should be possible to upgrade the installation.
+This documentation is meant to capture the changes made during an upgrade.
+
+```{versionchanged} 1.0.0
+Ensuring upgrades work has only been done since 1.0.0 upgrading from version
+0.2.0.
+```
+
+## Changes to the system environment
+
+The [system environment](system-environment) is not meant to be influenced
+unless explicitly mentioned in the changelog, typically only during major
+version upgrades.
+
+## Changes to the hub environment
+
+The [hub environment](hub-environment) gets several packages upgraded based on
+version ranges specified in [tljh/requirements-hub-env.txt].
+
+## Changes to the user environment
+
+The [user environment](user-environment) gets is `jupyterhub` package upgraded,
+but no other packages gets upgraded unless explicitly mentioned in the
+changelog, typically only during major version upgrades.
+
+[tljh/requirements-hub-env.txt]: https://github.com/jupyterhub/the-littlest-jupyterhub/blob/HEAD/tljh/requirements-hub-env.txt