如何从容器内部运行podman？

Question

我想运行podman作为运行CI/CD管道的容器。然而，我一直从podman容器中得到这个错误:

$ podman info
ERRO[0000] 'overlay' is not supported over overlayfs
Error: could not get runtime: 'overlay' is not supported over overlayfs: backing file system is unsupported for this graph driver

我使用Jenkins Kubernetes插件来编写CI/CD管道，这些管道在Kubernetes集群中作为容器运行。我已经成功地编写了使用Docker-in-Docker容器来运行< code>docker build和< code>docker push命令的管道。

然而，在容器中运行Docker客户端和Docker守护程序会使CI/CD环境非常臃肿，难以配置，并且不适合使用。所以我想我可以使用podman从Dockerfiles构建Docker映像，而无需使用胖的Docker守护程序。

问题是，podman是如此之新，我以前从未见过有人尝试过，我也不是足够的podman专家来正确执行它。

因此，使用Ubuntu的podman安装说明，我创建了以下docker文件:

FROM ubuntu:16.04

RUN apt-get update -qq \
    && apt-get install -qq -y software-properties-common uidmap \
    && add-apt-repository -y ppa:projectatomic/ppa \
    && apt-get update -qq \
    && apt-get -qq -y install podman

# To keep it running
CMD tail -f /dev/null

因此，我构建了图像并运行如下：

# Build
docker build -t podman:ubuntu-16.04 .

# Run
docker run --name podman -d podman:ubuntu-16.04

然后，在正在运行的容器上运行此命令时，我得到一个错误：

$ docker exec -ti podman bash -c "podman info"

ERRO[0000] 'overlay' is not supported over overlayfs
Error: could not get runtime: 'overlay' is not supported over overlayfs: backing file system is unsupported for this graph driver

我在一台Ubuntu 16.04机器上安装了podman，并运行了相同的< code>podman info命令，得到了预期的结果:

host:
  BuildahVersion: 1.8-dev
  Conmon:
    package: 'conmon: /usr/libexec/crio/conmon'
    path: /usr/libexec/crio/conmon
    version: 'conmon version , commit: '
  Distribution:
    distribution: ubuntu
    version: "16.04"
  MemFree: 2275770368
  MemTotal: 4142137344
  OCIRuntime:
    package: 'cri-o-runc: /usr/lib/cri-o-runc/sbin/runc'
    path: /usr/lib/cri-o-runc/sbin/runc
    version: 'runc version spec: 1.0.1-dev'
  SwapFree: 2146758656
  SwapTotal: 2146758656
  arch: amd64
  cpus: 2
  hostname: jumpbox-4b3620b3
  kernel: 4.4.0-141-generic
  os: linux
  rootless: false
  uptime: 222h 46m 33.48s (Approximately 9.25 days)
insecure registries:
  registries: []
registries:
  registries:
  - docker.io
store:
  ConfigFile: /etc/containers/storage.conf
  ContainerStore:
    number: 0
  GraphDriverName: overlay
  GraphOptions: null
  GraphRoot: /var/lib/containers/storage
  GraphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
    Using metacopy: "false"
  ImageStore:
    number: 15
  RunRoot: /var/run/containers/storage
  VolumePath: /var/lib/containers/storage/volumes

有谁知道我如何修复此错误并让podman从容器中工作？

Answer 1

mihai对info的建议成功了，但是一旦我尝试，例如，run--rmdocker.io/library/hello-world，我就收到一个错误：

error creating network namespace for container …: mount --make-rshared /var/run/netns failed: "operation not permitted"
failed to mount shm tmpfs "/var/lib/containers/storage/vfs-containers/…/userdata/shm": operation not permitted

我只是通过为映像设置一个非root用户，然后在特权模式下运行容器来解决这个问题，这违背了练习的目的，因为DinD已经可以这样做了:

FROM ubuntu:18.04

RUN apt-get update -qq \
    && apt-get install -qq -y software-properties-common uidmap \
    && add-apt-repository -y ppa:projectatomic/ppa \
    && apt-get update -qq \
    && apt-get -qq -y install podman \
    && apt-get install -y iptables

RUN adduser --disabled-login --gecos test test

USER test

ENTRYPOINT ["podman", "--storage-driver=vfs"]
CMD ["info"]

用作

docker build -t podman:test .
docker run --rm --privileged podman:test run --rm docker.io/library/hello-world

Answer 2

我自己尝试了更宽松的配置（--privileged=true），从主机安装了存储卷，并且在容器中安装了iptables并能够运行它（即sudo apt get install iptables）。

$ podman run -it --rm -v /var/run/containers/storage:/var/run/containers/storage -v /var/lib/containers/storage:/var/lib/containers/storage --storage-driver=overlay --privileged=true  mine bash
root@e275668d7c36:/# apt-get install -y -qq iptables
...
root@e275668d7c36:/# podman info
host:
  BuildahVersion: 1.8-dev
  Conmon:
    package: 'conmon: /usr/libexec/crio/conmon'
    path: /usr/libexec/crio/conmon
    version: 'conmon version , commit: '
  Distribution:
    distribution: ubuntu
    version: "16.04"
  MemFree: 71659520
  MemTotal: 482099200
  OCIRuntime:
    package: 'cri-o-runc: /usr/lib/cri-o-runc/sbin/runc'
    path: /usr/lib/cri-o-runc/sbin/runc
    version: 'runc version spec: 1.0.1-dev'
  SwapFree: 0
  SwapTotal: 0
  arch: amd64
  cpus: 2
  hostname: e275668d7c36
  kernel: 4.15.0-1035-aws
  os: linux
  rootless: false
  uptime: 315h 17m 53s (Approximately 13.12 days)
insecure registries:
  registries: []
registries:
  registries: []
store:
  ConfigFile: /etc/containers/storage.conf
  ContainerStore:
    number: 2
  GraphDriverName: overlay
  GraphOptions: null
  GraphRoot: /var/lib/containers/storage
  GraphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
    Using metacopy: "false"
  ImageStore:
    number: 4
  RunRoot: /var/run/containers/storage
  VolumePath: /var/lib/containers/storage/volumes

如果您想使用docker，也可以使用--privileged标志。

请记住，还有其他专门设计用于构建容器的工具，其中一些没有特权模式：

• 卡尼科
• img
• Buildkit
• Buildah（波德曼的同伴）
• Bazel（及其容器构建模块）
• Knative容器构建模板

Answer 3

您的Dockerfile也应该安装iptables：

FROM ubuntu:16.04

RUN apt-get update -qq \
    && apt-get install -qq -y software-properties-common uidmap \
    && add-apt-repository -y ppa:projectatomic/ppa \
    && apt-get update -qq \
    && apt-get -qq -y install podman \
    && apt-get install -y iptables

# To keep it running
CMD tail -f /dev/null

然后使用以下命令运行该命令：

docker run -ti --rm podman:test bash -c "podman --storage-driver=vfs info"

这应该会给你预期的反应。