run chroot within docker

Question

I've a commercial app, that is shipped in a chroot environment : the startup script is making the chroot, and starting the exe.

The App is pretty complex, and also for support purposes, I don't want to change the all environment.

Is it possible to run chroot, and start the service in docker ? Or are the two incompatible ?

Solution 1

It is possible to make a chroot inside a container... but, as mentioned in "debootstrap inside a docker container", you might need to run with the privileged mode.

docker run --privileged

By default, Docker containers are “unprivileged” and cannot, for example, run a Docker daemon inside a Docker container.
This is because by default a container is not allowed to access any devices, but a “privileged” container is given access to all devices.

There was a huge discussion for requesting docker to support privileged operations.
So far, it is not happening.

Solution 2

Option --cap-add=SYS_CHROOT should do the job.

Comments

[OpenStove]

How would you incorporate this in a supervisor configuration ? : - I need to make the chroot, - Then start 3 skripts

[VonC]

@OpenStove Have a look at github.com/phusion/baseimage-docker which is using a supervisor-like mechanism (I described it in stackoverflow.com/a/33119321/6309). You would still need to run the container in privieged mode though.