How to use Docker with ROS + real-time kernel? [closed]

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Dear ROS & Docker Users,

tl;dr: How to run Docker with linux real-time kernel (4.18.16-rt9)? What kernel features should I turn on during rt kernel compilation? I would appreciate your help.

The error I get:

$ docker run hello-world
docker:
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?.
See 'docker run --help'.

and:

$ docker info
Client:  Debug Mode:
false Server: ERROR: Cannot connect to the Docker daemon at unix:///var/run/docker.sock.
Is the docker daemon running?
errors pretty printing info

Preemption Model set during kernel compilation is: Fully Preemptible Kernel (RT) (PREEMPT_RT_FULL) (NEW)

Full description:

Hi, my name is Jakub and this is my first post on the forum. I am happy to change from "read-only mode" and join the community. I am volunteering to set up Docker on Ubuntu 18.04 with real-time kernel 4.18.16-rt9 for a robotic application in an academic setting. Docker will not run critical real-time tasks in this application, but the intention is to deploy partially containerized system on one machine to simplify the setup and testing with different software versions.

Unfortunately, I cannot start Docker on my setup. I think that 4.18.16-rt9 kernel causes the issues, because otherwise Docker works fine when I boot to 5.0.0-37 kernel on this system.

I have already tried the following:

• fully removed Docker and reinstalled it on my system.
• made sure that docker group exists and no sudo is required for Docker. Rebooted machine a few times while changing settings.

• Tried to enable Docker in three ways:

  systemctl enable docker.service
  systemctl start docker systemctl
  enable docker

• Found relevant unsolved GitHub issue and tied to run the image with --cap-add sys_nice and --privileged options.

• Checked for some kernel feature required to run Docker (as suggested here) and found that only my 5.0.0-37 kernel was found:

$ find /lib -iname 'aufs' /lib/modules/5.0.0-37-generic/kernel/fs/aufs
/lib/modules/5.0.0-37-generic/kernel/fs/aufs/aufs.ko
/lib/modules/5.0.0-36-generic/kernel/fs/aufs
/lib/modules/5.0.0-36-generic/kernel/fs/aufs/aufs.ko

Other relevant information:

• journalctl -u docker.service last lines available here, all the output is here.

$ journalctl -u docker.service  
(I skipped pasting some warning lines)
Dec 17 14:39:56 w530 dockerd[16869]:  
time="2019-12-17T14:39:56.843093125-05:00" level=warning msg="Your ke  
Dec 17 14:39:56 w530 dockerd[16869]:  
time="2019-12-17T14:39:56.843813184-05:00" level=info msg="Loading co  
Dec 17 14:39:56 w530 dockerd[16869]:
time="2019-12-17T14:39:56.882073092-05:00" level=warning msg="Running  
Dec 17 14:39:57 w530 dockerd[16869]:
time="2019-12-17T14:39:57.044629860-05:00" level=info msg="stopping e  
Dec 17 14:39:57 w530 dockerd[16869]:
time="2019-12-17T14:39:57.045272056-05:00" level=info msg="stopping e  
Dec 17 14:39:57 w530 dockerd[16869]: failed to start
daemon: Error initializing network
controller: error  
Dec 17 14:39:57 ...