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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

podman unshare cat /proc/self/uid_map

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"

If you change UID/GID mappings or the sysctl either reboot or

podman system migrate

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

Systemd Integration

podman generate systemd --new --name <unit name>
systemctl enable <unit name>
systemctl start <unit name>

Registry Configuration

See /etc/containers/registries.conf

To configure air-gapped mirror add:

unqualified-search-registries = ['mymirror.example.com']

[[registry]]
prefix = "docker.io"
location = "mymirror.example.com/somepath"

Handling other architectures

# Check which architectures have been pulled
podman image inspect docker.io/debian | jq -r '.[] | .Architecture'

# Check which architectures are available
podman manifest inspect docker.io/debian | grep architecture

podman pull --arch=arm debian:latest

Note that there is no buildx command like in docker. You need to use Buildah for building/running non-host-architecture images.

Misc