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  1. Jenkins
  2. JENKINS-66568

Pipeline withDockerContainer (docker-in-docker) unable to detect running inside container with cgroups v2

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      Description

      Running the pipeline taken from https://www.nixknight.com/2021/04/jenkins-docker-in-docker/ works fine in case of cgroups v1 but fails for cgroups v2.

      pipeline {
        agent {
          docker {
            image "bash:5.1.4"
          }
        }
        stages {
          stage('Donkey Work') {
            steps {
              sh '''
              if grep -sq 'docker' /proc/1/cgroup ; then
                echo -e "I'm running in a docker container."
              fi
              '''
            }
          }
        }
      }
      
      Result (cgroups v1)

      -> Jenkins seems to be running inside container 3a9...acc

      [Pipeline] withDockerContainer
      Jenkins seems to be running inside container 3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      $ docker run -t -d -u 1000:1000 -w /var/jenkins_home/workspace/test --volumes-from 3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** bash:5.1.4 cat
      $ docker top 4cf8f914963f286da3a9a830ae37b68463e12d822fe9811548a66a4694dd0139 -eo pid,comm
      [Pipeline] {
      [Pipeline] stage
      [Pipeline] { (Donkey Work)
      [Pipeline] sh
      + grep -sq docker /proc/1/cgroup
      + echo -e 'I'"'"'m running in a docker container.'
      I'm running in a docker container.
      [Pipeline] }
      [Pipeline] // stage
      [Pipeline] }
      
      Result (cgroups v2)

      -> Jenkins does not seem to be running inside a container

      [Pipeline] withDockerContainer
      Jenkins does not seem to be running inside a container
      $ docker run -t -d -u 1000:1000 -w /var/jenkins_home/workspace/test -v /var/jenkins_home/workspace/test:/var/jenkins_home/workspace/test:rw,z -v /var/jenkins_home/workspace/test@tmp:/var/jenkins_home/workspace/test@tmp:rw,z -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** -e ******** bash:5.1.4 cat
      $ docker top 3a6ec19ad44c8d4f9390c64f83b26f3a31fe6f5224a9c05ea63ed2e32f431563 -eo pid,comm
      [Pipeline] {
      [Pipeline] stage
      [Pipeline] { (Donkey Work)
      [Pipeline] sh
      process apparently never started in /var/jenkins_home/workspace/test@tmp/durable-097b92c0
      (running Jenkins temporarily with -Dorg.jenkinsci.plugins.durabletask.BourneShellScript.LAUNCH_DIAGNOSTICS=true might make the problem clearer)
      [Pipeline] }
      [Pipeline] // stage
      [Pipeline] }
      

      Further investigation shows that detecting if the process runs within a docker container is currently not easily feasible for cgroups v2, see: https://stackoverflow.com/questions/67155739/how-to-check-if-process-runs-within-a-docker-container-cgroup-v2-linux-host. However, I was wondering if this is a known issue and if anyone is trying to come up with a solution?

      cgroups v1
      $ cat /proc/1/cgroup
      12:pids:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      11:hugetlb:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      10:freezer:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      9:cpu,cpuacct:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      8:memory:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      7:devices:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      6:perf_event:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      5:cpuset:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      4:net_cls,net_prio:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      3:rdma:/
      2:blkio:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      1:name=systemd:/docker/3a930717d4967175b00e0e42f8756fe6cf508448b75fdd4763a02eb6d913eacc
      0::/system.slice/containerd.service
      
      cgroups v2
      $ cat /proc/1/cgroup
      0::/
      

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              Reporter:
              chrisss404 Christian
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