Container Wrapper
The Container Wrapper extension allows running a build step inside the specified Docker/LXC image. Images are pulled via docker pull or podman pull commands, depending on which container manager is installed on the agent that runs the build.
The extension is available for the following build runners:
Container Settings
In the Container Settings section of the build step settings, you can specify an image which will be used to run the build step. Once the image is specified, the following options become available.
Setting | Description |
|---|---|
Run step within container | The image name as stated in Docker Hub or other registry. TeamCity will start a container from the specified image and will try to run this build step within this container. For example, If an agent that runs the build has Podman installed instead of Docker, use either full image names (for example, |
Image platform | Select <Any> (default), Linux, or Windows. Note that Windows images are not supported by Podman. |
Pull image explicitly | If enabled, the image will be pulled from the Hub repository via |
Additional run arguments | Allows specifying additional options for the |
How Container Wrapper Works
Technically, the command of the build runner is wrapped in a shell script, and this script is executed inside a container with the docker run or podman run command. To view the details about the started process, text of the script, and so on, check the build log in Verbose mode.
The Container Wrapper maps paths to the build checkout directory and other agent directories like buildAgent/work, so that all these directories have the same location on a build agent and inside a Container Wrapper.
If the process environment contains the TEAMCITY_DOCKER_NETWORK environment variable set by the previous Docker Compose build step, this network is passed to the started docker run command with the --network switch.
Restoring File Ownership on Linux
Build agents that use Docker execute the chown command at the end of each step running inside a container to restore the buildAgent user's permissions to access the checkout directory. This action prevents potential issues related to build agents being unable to remove no longer needed container files that were created with the root ownership. Agents using Podman do not perform this step.
By default, a TeamCity agent uses the busybox image from Docker Hub to run the chown command. You can specify an alternative image name with the teamcity.internal.docker.busybox parameter, either in the buildAgent.properties file or in the build configuration parameters.
Environment Variables Handling
TeamCity passes environment variables from the build configuration into the Docker or Podman process, but it does not pass environment variables from the build agent, as they may not be relevant to the container environment. The list of the passed environment variables can be seen in the Verbose mode in the build log.
Setting Image Entrypoint
If a Docker image does not define an ENTRYPOINT, you can use still run a container with an ENTRYPOINT from the command line:
Add a Command Line build step.
Set the Run mode to Executable with parameters.
In the Command executable field, specify the full path to the
ENTRYPOINTin the target container.In Docker Settings, specify the name of the container.
TeamCity will start the specified Docker image with the defined ENTRYPOINT.