No Output From Container

I’m using the resin/raspberrypi3-node image on a Resin application, and the container fails to output terminal logs to the main Resin dashboard.

After doing a little hunting as to how the output from the container would be suppressed, I came across this github issue that states at some point that only the process with PID 1 will output from the container. I believe this is happening in the node container I’m trying to use - when I run ps aux, PID 1 is root 1 ... /sbin/init quiet systemd.show_status=0, the systemd init process. This process is initiated from this line in my Dockerfile, ENV INITSYSTEM on. The process that I would like to output to the terminal is the main /bin/bash process that just invokes npm start.

My questions:

  1. Do I need the systemd step if all I’m doing is running npm start in this container? Is something happening in the underlying resin/raspberrypi3-node container that needs this?
  2. Can I switch the process that I want into place to get its output instead?

Hey @dagrooms52,

  1. The init-system has a few benefits the main one is that because it’s PID 1, even if you’re node app fails the container will keep running, allowing you to ssh in and see what went wrong.
  2. Your node app should still be routing your logs to stdout, could you upload a small example somewhere so I can try and reproduce?

My question may have been misleading, I’m running this node container inside a Docker instance in the top-level container that Resin gives me (the docker-in-docker hack). I realized that the top-level container in Resin outputs all of its logs, but when running Docker inside this container it only gets the logs from PID 1 of each of its containers.

So what I really need is a way to get the output of a different process other than PID 1, or pick up all stdout from the docker-in-docker instance, since it still sounds beneficial to run init-system as PID 1.

Ah I see, you should be able to pipe the output from the child process into the main process, similar to what @justin8 did with his docker-in-docker approach:

If you’re looking to run multiple things inside the container, I’d recommend checking out the S6 overlay, which use here:

It’s pretty good if you have an app that also needs something like cron running or a secondary process or whatever, and provides simple ways to output logs from processes to stdout of PID 1.

Thanks guys, great resources - I’ll try to get something working with this info.

Did the resources provided by the community end up helping?
If things worked I don’t suppose you’d mind a quick summary for those who land here after a web search would you?

Sorry for the lack of follow-up; as you know, other features get in the way, and playing around with the core functionality gets put on the back burner. I ended up disabling init-system so that I can see my output while I develop, but eventually I’ll get around to re-enabling it and get everything playing nicely together.

Thanks again!