Update troubleshooting guide to deal with rootless path
We had a breaking change to rootless containers' temporary files
directories in Podman 0.11.1. Document a workaround to make the
change no longer working.
@@ -68,4 +68,36 @@ communicate with a registry and not use tls verification.
* Turn off tls verification by passing false to the tls-verification option.
* I.e. `podman push --tls-verify=false alpine docker://localhost:5000/myalpine:latest`
+
+---
+### 4) Rootless: could not get runtime - database configuration mismatch
+
+In Podman release 0.11.1, a default path for rootless containers was changed,
+potentially causing rootless Podman to be unable to function. The new default
+path is not a problem for new installations, but existing installations will
+need to work around it with the following fix.
+
+#### Symptom
+
+```console
+$ podman info
+could not get runtime: database run root /run/user/1000/run does not match our run root /run/user/1000: database configuration mismatch
+```
+
+#### Solution
+
+To work around the new default path, we can manually set the path Podman is
+expecting in a configuration file.
+
+First, we need to make a new local configuration file for rootless Podman.
+* `mkdir -p ~/.config/containers`
+* `cp /usr/share/containers/libpod.conf ~/.config/containers`
+
+Next, edit the new local configuration file
+(`~/.config/containers/libpod.conf`) with your favorite editor. Comment out the
+line starting with `cgroup_manager` by adding a `#` character at the beginning
+of the line, and change the path in the line starting with `tmp_dir` to point to
+the first path in the error message Podman gave (in this case,
+`/run/user/1000/run`).
+
---
