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Podman Cheat Sheet

CLI Usage

Podman is CLI compatible to Docker. See the Docker cheat sheet.

Docker compatibility

By default Podman supports only OCI images, so some docker stuff like

SHELL ["/bin/bash", "-o", "pipefail", "-c"]

does not work. To still use it switch to Docker format when building

podman build --format docker .

Running without root

Things to test

cat /etc/subuid /etc/subgid                     # -> should print user definitions    
getcap /usr/bin/newuidmap /usr/bin/newgidmap    # -> should print "cap_setuid+ep"

sysctl -a | grep kernel.unprivileged_userns_clone  # -> should be "1"

e.g. in a k8s build pod, might cause

newuidmap: write to uid_map failed: Operation not permitted

Can be solved by

chmod 4755 /usr/bin/newgidmap
chmod 4755 /usr/bin/newuidmap