Podman quadlet: environment variables unavailable in Exec=

[ja-cop]

Issue Description

With Quadlet, environment variables introduced via EnvironmentFile= are available inside the container, but it doesn't seem like they can be used to supply command line arguments to the container's command via Exec=.

Maybe this is expected behavior and I'm just missing something about how this is supposed to work?

Steps to reproduce the issue

$ cat /etc/containers/systemd/users/1000/debug.container 
[Container]
Image=docker.io/library/busybox:latest
ContainerName=debug
EnvironmentFile="%E/debug/env"
Exec=echo "test: ${FOO}"

$ cat ~/.config/debug/env
FOO=hello

$ systemctl --user start debug
$ journalctl --user -u debug

Describe the results you received

In the log output, there is a helpful warning:

debug.service: Referenced but unset environment variable evaluates to an empty string: FOO

And the output of the Exec= command itself:

test: ''

Describe the results you expected

I would have expected ${FOO} to be available at the Exec= command line as well, the way regular systemd service files behave AFAIK.

podman info output

Podman Version: 5.3.1
OS: Arch Linux
Architecture: linux/amd64

Podman in a container

No

Privileged Or Rootless

Rootless

Upstream Latest Release

Yes

Additional environment details

No response

Additional information

No response

[ygalblum]

You have two layers of issues:

1. The code that runs under the Exec command does not inherit the shell environment variables set to the container. This is true regardless to Quadlet. So, in order to be able to access these variables, you need to run your command in a new shell.
2. When using Quadlet (and as a result systemd) there are two layers of variables substitution. First, systemd and then the container itself. The warning you see comes from systemd as it is unable to find a value for FOO . But, you never intended for it to look for FOO. So, to have systemd disregard the substitution, you need to escape the $ sign.

Combing the two you Exec line should be:

Exec=/bin/sh -c 'echo "test: $${FOO}"'

[Luap99]

Or the alternative if the env var does not need to be in the container at all you can set it under the systemd service section.
https://www.freedesktop.org/software/systemd/man/latest/systemd.exec.html#Environment

[Service]
EnvironmentFile=...

[Container]
...
Exec=echo "test: ${FOO}"

With that systemd should replace the var before passing that to podman.

[ja-cop]

Thanks both of you! I think putting EnvironmentFile= in [Service] is what I want. I didn't realize I could still add [Service] directives myself when using a Quadlet-generated service file.