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--- title: Override entrypoint in container instance description: Set a command line to override the entrypoint in a container image when you deploy an Azure container instance ms.topic: how-to ms.author: tomcassidy author: tomvcassidy ms.service: azure-container-instances ms.custom: devx-track-azurecli services: container-instances ms.date: 11/17/2025 # Customer intent: As a container administrator, I want to override the default entrypoint in a container instance, so that I can customize command execution for specific tasks or batch jobs. --- # Set the command line in a container instance to override the default command line operation When you create a container instance, optionally specify a command to override the default command line instruction baked into the container image. This behavior is similar to the `--entrypoint` command-line argument to `docker run`. Like setting [environment variables](container-instances-environment-variables.md) for container instances, specifying a starting command line is useful for batch jobs where you need to prepare each container dynamically with task-specific configuration. ## Command line guidelines * By default, the command line specifies a *single process that starts without a shell* in the container. For example, the command line might run a Python script or executable file. The process can specify additional parameters or arguments. * To execute multiple commands, begin your command line by setting a shell environment that is supported in the container operating system. Examples: |Operating system |Default shell | |---------|---------| |Ubuntu | `/bin/bash` | |Alpine | `/bin/sh` | |Windows | `cmd` | Follow the conventions of the shell to combine multiple commands to run in sequence. * Depending on the container configuration, you might need to set a full path to the command line executable or arguments. * Set an appropriate [restart policy](container-instances-restart-policy.md) for the container instance, depending on whether the command-line specifies a long-running task or a run-once task. For example, a restart policy of `Never` or `OnFailure` is recommended for a run-once task. * If you need information about the default entrypoint set in a container image, use the [docker image inspect](https://docs.docker.com/engine/reference/commandline/image_inspect/) command. ## Command line syntax The command line syntax varies depending on the Azure API or tool used to create the instances. If you specify a shell environment, also observe the command syntax conventions of the shell. * [az container create][az-container-create] command: Pass a string with the `--command-line` parameter. Example: `--command-line "python myscript.py arg1 arg2"`). * [New-AzContainerGroup][new-azcontainergroup] Azure PowerShell cmdlet: Pass a string with the `-Command` parameter. Example: `-Command "echo hello"`. * Azure portal: In the **Command override** property of the container configuration, provide a comma-separated list of strings, without quotes. Example: `python, myscript.py, arg1, arg2`). * Resource Manager template or YAML file, or one of the Azure SDKs: Specify the command line property as an array of strings. Example: the JSON array `["python", "myscript.py", "arg1", "arg2"]` in a Resource Manager template. If you're familiar with [Dockerfile](https://docs.docker.com/engine/reference/builder/) syntax, this format is similar to the *exec* form of the CMD instruction. ### Examples | | Azure CLI | Portal | Template | | ---- | ---- | --- | --- | | **Single command** | `--command-line "python myscript.py arg1 arg2"` | **Command override**: `python, myscript.py, arg1, arg2` | `"command": ["python", "myscript.py", "arg1", "arg2"]` | | **Multiple commands** | `--command-line "/bin/bash -c 'mkdir test; touch test/myfile; tail -f /dev/null'"` |**Command override**: `/bin/bash, -c, mkdir test; touch test/myfile; tail -f /dev/null` | `"command": ["/bin/bash", "-c", "mkdir test; touch test/myfile; tail -f /dev/null"]` | ## Azure CLI example As an example, modify the behavior of the microsoft/aci-wordcount container image, which analyzes text in Shakespeare's *Hamlet* to find the most frequently occurring words. Instead of analyzing *Hamlet*, you could set a command line that points to a different text source. To see the output of the microsoft/aci-wordcount container when it analyzes the default text, run it with the following [az container create][az-container-create] command. No start command line is specified, so the default container command runs. For illustration purposes, this example sets [environment variables](container-instances-environment-variables.md) to find the top three words that are at least five letters long: ```azurecli-interactive az container create \ --resource-group myResourceGroup \ --name mycontainer1 \ --image mcr.microsoft.com/azuredocs/aci-wordcount:latest \ --environment-variables NumWords=3 MinLength=5 \ --restart-policy OnFailure ``` Once the container's state shows as *Terminated* (use [az container show][az-container-show] to check state), display the log with [az container logs][az-container-logs] to see the output. ```azurecli-interactive az container logs --resource-group myResourceGroup --name mycontainer1 ``` ```output [('HAMLET', 386), ('HORATIO', 127), ('CLAUDIUS', 120)] ``` Now set up a second example container to analyze different text by specifying a different command line. The Python script executed by the container, *wordcount.py*, accepts a URL as an argument, and processes that page's content instead of the default. For example, to determine the top three words that are at least five letters long in *Romeo and Juliet*: ```azurecli-interactive az container create \ --resource-group myResourceGroup \ --name mycontainer2 \ --image mcr.microsoft.com/azuredocs/aci-wordcount:latest \ --restart-policy OnFailure \ --environment-variables NumWords=3 MinLength=5 \ --command-line "python wordcount.py http://shakespeare.mit.edu/romeo_juliet/full.html" ``` Again, once the container is *Terminated*, view the output by showing the container's logs: ```azurecli-interactive az container logs --resource-group myResourceGroup --name mycontainer2 ``` ```output [('ROMEO', 177), ('JULIET', 134), ('CAPULET', 119)] ``` ## Next steps Task-based scenarios, such as batch processing a large dataset with several containers, can benefit from custom command lines at runtime. For more information about running task-based containers, see [Run containerized tasks with restart policies](container-instances-restart-policy.md). <!-- LINKS - External --> [aci-wordcount]: https://hub.docker.com/_/microsoft-azuredocs-aci-wordcount <!-- LINKS Internal --> [az-container-create]: /cli/azure/container#az_container_create [az-container-logs]: /cli/azure/container#az_container_logs [az-container-show]: /cli/azure/container#az_container_show [new-azcontainergroup]: /powershell/module/az.containerinstance/new-azcontainergroup