Optimize the S6 Images work with PaaS hosts (fixing the error "s6-overlay-suexec: fatal: can only run as pid 1")

[jaydrogers]

Problem

Some hosts expect to have PID 1 and it causes this error to display:

s6-overlay-suexec: fatal: can only run as pid 1

Known Hosts with this issue

• Fly.io
• Heroku
• ECS Fargate

References:

These are the related discussions we've seen to this issue:

• https://discord.com/channels/910287105714954251/910299240897605632/1095593392035082341
• s6-overlay-suexec: fatal: can only run as pid 1 #87
• Deploying to ECS Fargate #189

Proposed solution

• Reach out to the team at S6 Overlay to see if they have any known workarounds (https://github.com/just-containers/s6-overlay)
• Reach out to the PaaS hosts and see if they support releasing PID 1 to S6 overlay

[jaydrogers]

Update: S6 Overlay maintainer has some thoughts

One of the maintainers of S6 Overlay commented on this here: just-containers/s6-overlay#535 (comment)

It sounds like ECS Fargate doesn't give you control over your process 1 by default. You should check with their documentation whether they are running their own init and if there's a way to bypass it.

If it's unavoidable, then they're not providing you with a real container environment, but a functionality-reduced simile of it, and you'll be unable to run s6-overlay on that platform. Sorry.

[moisish]

For the ECS, I think i have found the issue. By disabling the init process, everything works as expected

InitProcessEnabled
Run an init process inside the container that forwards signals and reaps processes. This parameter maps to the --init option to [docker run](https://docs.docker.com/engine/reference/run/#security-configuration).

[mpskovvang]

I was struggling with the same error on Fly.io.

Switching the image variant from FPM-NGINX to Unit solved the issue with no further changes since Unit is not using the S6 Overlay.