How to deploy application containers

swmodd support deployment of application containers which support OCI image and runtime formats using CRUN.

How to create an application container tar

To convert an docker image to OCI application container, we need to use skopeo and umoci utilities.

In below exaple httpd docker container is used - Create an empty directory in local laptop/desktop

$ mkdir lcm
$ cd lcm

• Copy the docker image using skopeo, make sure to use correct tag as per the target architecture

$ skopeo copy docker://httpd:latest oci:httpd_copy:latest

• Unpack the downloaded image in OCI format using umoci

$ sudo -i
# cd <working_dir_path>
# umoci unpack --image httpd_copy:latest httpd

• Move to the directory containing config.json and rootfs and create a tar

# cd httpd
# tar cf ../httpd.tar *

• Use this tar in install_du ubus command to deploy the application container

Sulu application container

An example makefile to generate sulu application container tar ball can be accessed here

Local application containers with multi-arch support

It is possible to create an multi-arch oci container and store it in Gitlab image registry, to support variety of devices and platforms.

This can be done in many ways, but in this example I am using docker buildx to build multi-arch containers.

Pre-setup

1. Create a access-token with read/write access to image registry in gitlab
2. Install buildx

export BUILDX_VERSION="v0.10.4"
export BUILDX_ARCH="linux-amd64"
wget -O /usr/bin/docker-buildx https://github.com/docker/buildx/releases/download/${BUILDX_VERSION}/buildx-${BUILDX_VERSION}.${BUILDX_ARCH}

Build

To build a multi-arch oci container and push to Gitlab image registry, run following commands, sulu example container used in this example:

$ docker-buildx create --use
$ cd examples/sulu
$ make extract
$ docker-buildx build --provenance=false --platform linux/386,linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64/v8 --tag dev.iopsys.eu:5050/lcm/swmodd/sulu:v2.1.2 --push .

Above commands creates sulu multi-arch containers and push it to Gitlab image registry.

Verify

Image details can be verified with docker manifest command:

vdutta@SW019:~$ docker manifest inspect dev.iopsys.eu:5050/lcm/swmodd/sulu
{
   "schemaVersion": 2,
   "mediaType": "application/vnd.docker.distribution.manifest.list.v2+json",
   "manifests": [
      {
         "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
         "size": 1871,
         "digest": "sha256:5d362624ae3d27ecea7486a6b8f6a103b7d52543574baa483dd9034402727eb5",
         "platform": {
            "architecture": "386",
            "os": "linux"
         }
      },
      {
         "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
         "size": 1871,
         "digest": "sha256:db776d064d0763874bca5f8c4a5f396e339a901350cbcc8714c5e19c3adcefc9",
         "platform": {
            "architecture": "amd64",
            "os": "linux"
         }
      },
      {
         "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
         "size": 1871,
         "digest": "sha256:0323e482ca40f631a46993736b65459554149ac1586f04042cf61e738236bc64",
         "platform": {
            "architecture": "arm",
            "os": "linux",
            "variant": "v5"
         }
      },
      {
         "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
         "size": 1871,
         "digest": "sha256:63d6bcea175828b4a8034b874948e774e40eea8f71657c6e0d7a4d5881662db8",
         "platform": {
            "architecture": "arm",
            "os": "linux",
            "variant": "v6"
         }
      },
      {
         "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
         "size": 1871,
         "digest": "sha256:29152f374de66400c489413c2fcddfd26b8edad4c048efea57b0c17f07aa05ed",
         "platform": {
            "architecture": "arm",
            "os": "linux",
            "variant": "v7"
         }
      }
   ]
}
vdutta@SW019:~$

Above output provides the sha1 hash per architechture, to use a specific image in device, it can be used with its sha checksum hash, like below

obuspa -c operate "Device.SoftwareModules.InstallDU(URL=docker://dev.iopsys.eu:5050/lcm/swmodd/sulu@sha256:0323e482ca40f631a46993736b65459554149ac1586f04042cf61e738236bc64)"

This installs sulu for arm/v5 arch.