The version of Podman that is available on Oracle Linux 8 has an issue unmounting the overlay file system for a container when performing an rm operation while using the --uidmap option. The issue typically manifests with output similar to the following:

ERRO[0000] error unmounting
/var/lib/containers/storage/overlay/9bf314b8c2411fd7b7e2f249671bead918a7aaffec
a8299a602b525c061c1cd3/merged: invalid argument

The following error appears in the dmesg log:

[  848.192546] overlayfs: failed to verify upper
(9bf314b8c2411fd7b7e2f249671bead918a7aaffeca8299a602b525c061c1cd3/diff,
ino=101428727, err=-116)
[  848.198470] overlayfs: failed to verify index dir 'upper' xattr
[  848.200809] overlayfs: try deleting index dir or mounting with '-o
index=off' to disable inodes index.

The default handling for the overlay file system on UEK R6 is to mount with the index option enabled. This feature uses use the index directory to map lower inodes to upper inodes by default, however the impact of turning it off is negligible. If you experience this issue, it can be avoided by loading the overlay module with the index=off option set. For example, run:

sudo rmmod overlay 
sudo modprobe overlay index=off

To make these settings persistent, set this option in /etc/modprobe.d/. For example, run the following:

echo 'options overlay index=off' | sudo tee /etc/modprobe.d/overlay.conf

(Bug ID 31025483)