OK, so, I have a thing I wrote (https://github.com/lojban/lbcs) that does its own simple isolated rootless container management. It starts a pod and then starts a configurable list of containers within the pod. https://github.com/containers/podman/issues/12669#issuecomment-998845927 completely broke one of my setups. Which is fine, but I want to know what I should be doing instead. I'm sure it's possible that where I'm going wrong is not where I'm expecting, so I'm going to try to lay out the whole situation. Here's the situation. I have a pod in which I run exim, spamassassin, and clamav. I'm running it rootless, as a user made for this purpose. Let's say the user's UID is 1000, cuz, you know, tradition. I have several things mounted into the containers as a method of persistence, such as exim's spool directory, clamav's definitions dir, etc. Because I'm running rootless, all those files are owned by UID 1000, as you'd expect. I also run with --userns=keep-id, because, well, that seems cleanest and most secure? Running thigs as root in the container seems bad? I'm not sure I actually have a strong principled reason to be doing that, so let me know if it's a bad plan. However, daemons tend to want to run as their own user, so my standard pattern is: RUN for user in mail clamupdate clamscan ; \ do \ find / -xdev -user $user -print0 | xargs -r -0 chown <%= userid %> ; \ usermod -o -u <%= userid %> $user ; \ done , where "<%= userid %>" is replaced with "1000" by the templating thingy. So: change the UID of the system user that the daemon runs at to 1000, and change all files owned by that user to 1000. This all works fine, I do it in many places, it's fine. Here's the problem: exim will *only* run as UID 93. It is, I shit you not, baked in at compile time ;_;. (See https://src.fedoraproject.org/rpms/exim/blob/rawhide/f/exim-4.96-config.patc... and https://github.com/Exim/exim/blob/cf5f5988102b229ef87bc85ba3f0a9ec265f28a6/s... ). I'm running from the Fedora RPMs. I do not want to roll my own. I want to pass the network connection between clamav and exim across localhost, because why have the network connection transit out of containers? So what I *used* to have was: $ podman pod create --share=net --network slirp4netns:mtu=30000,port_handler=slirp4netns --userns=keep-id -n drata -p 20280:20280 -p 20225:20225 -p 20265:20265 --network slirp4netns:outbound_addr=192.168.123.132 $ podman run --pod=drata --log-driver=none --name exim -t --uidmap 0:1:92 --uidmap 93:0:1 --uidmap 94:95:8192 -v /home/spdrata/misc-containers/shared_data/var_spool/:/var/spool -v /home/spdrata/misc-containers/shared_data/srv_lojban:/srv/lojban -i spdrata/drata-exim:1 , and that worked fine. The uidmap maps the user running the rootless container (UID 1000) on the host to UID 93 in the container. (Side comment: the documentation for uidmap is *terrible*; coming up with that uidmap set to do what I want took me *hours* of experimentation.) This now simply refuses to work. So what I'm doing instead is I moved the uidmap onto the pod, instead of remapping all the system/daemon users to UID 1000, I remap them to UID 93. This seems ... icky?, but maybe it's the right way to do it? Honestly not sure. Looking for advice. Thanks if you read this far! :D