runc-rc1, new workflow and terminal=true containers

[papey]

Regarding the documentation, runc-rc1 (https://github.com/opencontainers/runc/releases/tag/v1.0.0-rc1) provide a new workflow based on 4 steps :

• create
• start
• kill
• delete

Readme specify that containers created with this new workflow have to be in "background mode" (terminal=false).

in the future, hooks will be removed from both in OCI and runC (see opencontainers/runtime-spec#483 and opencontainers/runtime-spec#483 for more info).

So how runC will handle the tty problem for terminal=true containers ?

I see three options here :

• Update the tty.go code to fit the new workflow
• Delegate tty management to users
• Use runc run for terminal=true containers

What is the "official" position of the runC dev team about this subject ?

Thanks for reading/answers

[athoune]

Maybe something like :

• runc create creates its own pty, don't detach and copy STDIN/STDOUT with the pty. Nothing happens.
• configure network stuff with nsenter
• runc start, a simple SIGCONT signal start the container.

It's ugly, but it handles the prepare/configure/step without hooks.

[cyphar]

This is probably related to the amiguity wrt terminal: true (opencontainers/runtime-spec#494), as well as lots of the issues with --console (#814).

You can use --console with runc create to specify a slave terminal (/dev/pts/X) that runC should use. You can see an example program using this facility here: https://gist.github.com/crosbymichael/aaca1f3d82bc90995045eb6b9f136d53

[papey]

@athoune Regarding changes made by #886, runC will no longer use signals to start the container process.

@cyphar yes but tty is so close to the runtime (tty life time == container process life time) that it makes sens to me that runc handle this task.

[cyphar]

To be clear: I think we should fix it. I was just pointing you to places where you can find some more information, as well as a workaround. I've been trying to figure out how to properly fix --console's interaction with user namespaces for a few weeks now.

/cc @crosbymichael

[cyphar]

@papey I've implemented a bunch of terminal changes in #1018. Take a look if you're interested (that PR will close this one once merged).

[cyphar]

#1018 has been merged.