How to read container's stdout when using passthough log driver?

[tkit1994]

[email protected] has switched to passthough log driver by default in podman version 4.4.0.
How can it read a container's stdout.

➜  journal podman logs alist-alist
Error: this container is using the 'passthrough' log driver, cannot read logs: this container is not logging output

➜  journal podman attach alist-alist
Error: attaching to container f9a23ad068936cee9e8a85e529fa35bc67717b7de1f6094265cc2c83abd62554: this container is using the 'passthrough' log driver, cannot attach: this container is not logging output

[vrothberg]

Thanks for reaching out, @tkit1994! Is this change breaking your deployment?

With passthrough, you can find the logs in the journal. You can use journalctl _PID=$PID_of_process for instance.

[tkit1994]

Thanks, it does not. Your solution works like a charm.

[vrothberg]

Excellent. Thanks a lot for reaching out!

[Luap99]

I was thinking maybe we can teach podman logs to still read from the journal even with passthrough when it is run in a systemd unit, we already set PODMAN_SYSTEMD_UNIT unit env so we can use the unit name to filter logs. Most of the code to read the journal correctly is already there, we just need to apply different filters and slightly change the message parsing logic.

[vrothberg]

Yes, that will work 👍

[rhatdan]

That sounds like a great idea.

[rrbanda]

@rhatdan is this specific to OS on which podman runs ?
Because i can see logs on a rocky linux for the same container but not on a CentOS 9

[rhatdan]

No there should be no diference on OS, but their could be difference on versions or how you have containers.conf configured between the two machines.