I want to run podman as a container to run CI/CD pipelines. However, I keep getting this error from the podman container:
$ 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
I am using the Jenkins Kubernetes plugin to write CI/CD pipelines that run as containers within a Kubernetes cluster. I've been successful at writing pipelines that use a Docker-in-Docker container to run docker build
and docker push
commands.
However, running a Docker client and a Docker Daemon inside a container makes the CI/CD environment very bloated, hard to configure, and just not ideal to work with. So I figured I could use podman to build Docker images from Dockerfiles without using a fat Docker daemon.
The problem is that podman is so new that I have not seen anyone attempt this before, nor I am enough of a podman expert to properly execute this.
So, using the podman installation instructions for Ubuntu I created the following Dockerfile:
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
So I built the image and ran it as follows:
# Build
docker build -t podman:ubuntu-16.04 .
# Run
docker run --name podman -d podman:ubuntu-16.04
Then when running this command on the running container, I get an error:
$ 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
I install podman on an Ubuntu 16.04 machine I had and ran the same podman info
command I got the expected results:
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
Does anyone know how I can fix this error and get podman working from a container?
Your Dockerfile should install iptables as well:
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
Then run the command with:
docker run -ti --rm podman:test bash -c "podman --storage-driver=vfs info"
This should give you the response you expect.
The suggestion from mihai succeeds for info
but as soon as I try, for example, run --rm docker.io/library/hello-world
I get an error:
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
I only managed to solve this by setting a non-root user for the image and then running the container in privileged mode, which defeats the purpose of the exercise since DinD could already do this:
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"]
used as
docker build -t podman:test .
docker run --rm --privileged podman:test run --rm docker.io/library/hello-world
I tried this myself with a more permissive config (--privileged=true
), with storage volumes mounted from the host and also with iptables
installed in the container and was able to run it (i.e 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
If you'd like to use docker
you can use the --privileged
flag too.
Keep in mind that there are other tools specifically designed to build containers and some of them without privileged mode: