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In this post, I walk through creating a simple Go web app that runs in a Docker container, and lists the hostname of the container it’s running in. I chose Go as I’ve recently gotten started writing code in Go and it’s a lot of fun to work with. The container will install Go, so there is no need to install it locally on your machine. Docker is a prerequisite, however. Installing Redis locally. Docker run –d –p 6379:6379 –name reddis redis. –d- running the container in the background. –name reddis –name of the container. 6379:6379 – exposing default redis port. When we are running the above-mentioned command locally, then it will take some time to download the copy from redis repository, then.
If you are working on a project that requires frequent copying of files and folders either from container to your local machine or from the local machine to the container, docker provides an easy and simple way to do that. If you have already built a docker image which is of large size and contains a large number of files and in the midst of the project you want to copy files to and from the container, it’s highly inefficient to put the files in the docker build context and build images repeatedly. Instead, docker allows easy copying of files to and from containers.
In this article, we will learn about the commands that will allow us to do so. We will look for commands for copying the files from both local machine to container and vice versa.
To copy a file from container to local machine.
If you want to copy a file from your container to your local machine, you can use the following command.
If you have an ubuntu container, with ID f4628571q5gc and you want to copy a file from path /usr/src/app/file.txt in the container to /home/username/Desktop/folder in the local machine, you can use the command -
If you want to paste the file in the current directory of you local machine, you can simply use -
If you want to copy all the files from a particular folder in container, to a folder in the local machine, use the following command -
To copy a file from local machine to container
If you want to copy a file from your local machine to a container, you can use the following command.
If you have an ubuntu container, with ID f4628571q5gc and you want to copy a file from path /home/username/Desktop/folder/file.txt in the local machine to /usr/src/app/ in the container, you can use the command -
If you want to copy all the files from a folder in your local machine to a folder in the container, use the following command -
To conclude, after you have already built an image with a build context and you want to copy files and folders to and from the container, you can easily do that using the commands mentioned above.
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Estimated reading time: 19 minutes
The Docker Azure Integration enables developers to use native Docker commands to run applications in Azure Container Instances (ACI) when building cloud-native applications. The new experience provides a tight integration between Docker Desktop and Microsoft Azure allowing developers to quickly run applications using the Docker CLI or VS Code extension, to switch seamlessly from local development to cloud deployment.
In addition, the integration between Docker and Microsoft developer technologies allow developers to use the Docker CLI to:
- Easily log into Azure
- Set up an ACI context in one Docker command allowing you to switch from a local context to a cloud context and run applications quickly and easily
- Simplify single container and multi-container application development using the Compose specification, allowing a developer to invoke fully Docker-compatible commands seamlessly for the first time natively within a cloud container service
Also see the full list of container features supported by ACI and full list of compose features supported by ACI.
To deploy Docker containers on Azure, you must meet the following requirements:
Download and install the latest version of Docker Desktop.
Alternatively, install the Docker Compose CLI for Linux.
Ensure you have an Azure subscription. You can get started with an Azure free account.
Run Docker containers on ACI
Docker not only runs containers locally, but also enables developers to seamlessly deploy Docker containers on ACI using
docker run or deploy multi-container applications defined in a Compose file using the
docker compose up command.
The following sections contain instructions on how to deploy your Docker containers on ACI.Also see the full list of container features supported by ACI.
Log into Azure
Run the following commands to log into Azure:
This opens your web browser and prompts you to enter your Azure login credentials.If the Docker CLI cannot open a browser, it will fall back to the Azure device code flow and lets you connect manually.Note that the Azure command line login is separated from the Docker CLI Azure login.
Alternatively, you can log in without interaction (typically inscripts or continuous integration scenarios), using an Azure ServicePrincipal, with
docker login azure --client-id xx --client-secret yy --tenant-id zz
Logging in through the Azure Service Provider obtains an access token validfor a short period (typically 1h), but it does not allow you to automaticallyand transparently refresh this token. You must manually re-loginwhen the access token has expired when logging in with a Service Provider.
You can also use the
--tenant-id option alone to specify a tenant, ifyou have several ones available in Azure.
Create an ACI context
After you have logged in, you need to create a Docker context associated with ACI to deploy containers in ACI.Creating an ACI context requires an Azure subscription, a resource group, and a region.For example, let us create a new context called
This command automatically uses your Azure login credentials to identify your subscription IDs and resource groups. You can then interactively select the subscription and group that you would like to use. If you prefer, you can specify these options in the CLI using the following flags:
If you don’t have any existing resource groups in your Azure account, the
docker context create aci myacicontext command creates one for you. You don’t have to specify any additional options to do this.
After you have created an ACI context, you can list your Docker contexts by running the
docker context ls command:
Run a container
Now that you’ve logged in and created an ACI context, you can start using Docker commands to deploy containers on ACI.
There are two ways to use your new ACI context. You can use the
--context flag with the Docker command to specify that you would like to run the command using your newly created ACI context.
Or, you can change context using
docker context use to select the ACI context to be your focus for running Docker commands. For example, we can use the
docker context use command to deploy an Nginx container:
After you’ve switched to the
myacicontext context, you can use
docker ps to list your containers running on ACI.
In the case of the demonstration Nginx container started above, the result of the ps command will display in column “PORTS” the IP address and port on which the container is running. For example, it may show
188.8.131.52:80->80/tcp, and you can view the Nginx welcome page by browsing
To view logs from your container, run:
To execute a command in a running container, run:
To stop and remove a container from ACI, run:
You can remove containers using
docker rm. To remove a running container, you must use the
--force flag, or stop the container using
docker stop before removing it.
The semantics of restarting a container on ACI are different to those when using a local Docker context for local development. On ACI, the container will be reset to its initial state and started on a new node. This includes the container’s filesystem so all state that is not stored in a volume will be lost on restart.
Running Compose applications
You can also deploy and manage multi-container applications defined in Compose files to ACI using the
docker compose command.All containers in the same Compose application are started in the same container group. Service discovery between the containers works using the service name specified in the Compose file.Name resolution between containers is achieved by writing service names in the
/etc/hosts file that is shared automatically by all containers in the container group.
Also see the full list of compose features supported by ACI.
Ensure you are using your ACI context. You can do this either by specifying the
--context myacicontextflag or by setting the default context using the command
docker context use myacicontext.
docker compose upand
docker compose downto start and then stop a full Compose application.
Run Docker Image Locally Ubuntu
docker compose up uses the
docker-compose.yaml file in the current folder. You can specify the working directory using the --workdir flag or specify the Compose file directly using
docker compose --file mycomposefile.yaml up.
You can also specify a name for the Compose application using the
--project-name flag during deployment. If no name is specified, a name will be derived from the working directory.
Containers started as part of Compose applications will be displayed along with single containers when using
docker ps. Their container ID will be of the format:
<COMPOSE-PROJECT>_<SERVICE>. These containers cannot be stopped, started, or removed independently since they are all part of the same ACI container group. You can view each container’s logs with
docker logs. You can list deployed Compose applications with
docker compose ls. This will list only compose applications, not single containers started with
docker run. You can remove a Compose application with
docker compose down.
The current Docker Azure integration does not allow fetching a combined log stream from all the containers that make up the Compose application.
From a deployed Compose application, you can update the application by re-deploying it with the same project name:
docker compose --project-name PROJECT up.
Updating an application means the ACI node will be reused, and the application will keep the same IP address that was previously allocated to expose ports, if any. ACI has some limitations on what can be updated in an existing application (you will not be able to change CPU/memory reservation for example), in these cases, you need to deploy a new application from scratch.
Updating is the default behavior if you invoke
docker compose up on an already deployed Compose file, as the Compose project name is derived from the directory where the Compose file is located by default. You need to explicitly execute
docker compose down before running
docker compose up again in order to totally reset a Compose application.
Single containers and Compose applications can be removed from ACI withthe
docker prune command. The
docker prune command removes deploymentsthat are not currently running. To remove running depoyments, you can specify
--dry-run option lists deployments that are planned forremoval, but it doesn’t actually remove them.
Single containers and Compose applications can optionally expose ports.For single containers, this is done using the
-p) flag of the
docker run command :
docker run -p 80:80 nginx.
For Compose applications, you must specify exposed ports in the Compose file service definition:
ACI does not allow port mapping (that is, changing port number while exposing port). Therefore, the source and target ports must be the same when deploying to ACI.
All containers in the same Compose application are deployed in the same ACI container group. Different containers in the same Compose application cannot expose the same port when deployed to ACI.
By default, when exposing ports for your application, a random public IP address is associated with the container group supporting the deployed application (single container or Compose application).This IP address can be obtained when listing containers with
docker ps or using
DNS label name
In addition to exposing ports on a random IP address, you can specify a DNS label name to expose your application on an FQDN of the form:
You can set this name with the
--domainname flag when performing a
docker run, or by using the
domainname field in the Compose file when performing a
docker compose up:
The domain of a Compose application can only be set once, if you specify the
domainname for several services, the value must be identical.
<DOMAINNAME>.region.azurecontainer.io must be available.
Using Azure file share as volumes in ACI containers
Run Mysql Docker Container Locally
You can deploy containers or Compose applications that use persistent datastored in volumes. Azure File Share can be used to support volumes for ACIcontainers.
Using an existing Azure File Share with storage account name
mystorageaccountand file share name
myfileshare, you can specify a volume in your deployment
runcommand as follows:
The runtime container will see the file share content in
In a Compose application, the volume specification must use the following syntaxin the Compose file:
The volume short syntax in Compose files cannot be used as it is aimed at volume definition for local bind mounts. Using the volume driver and driver option syntax in Compose files makes the volume definition a lot more clear.
In single or multi-container deployments, the Docker CLI will use your Azure login to fetch the key to the storage account, and provide this key with the container deployment information, so that the container can access the volume.Volumes can be used from any file share in any storage account you have access to with your Azure login. You can specify
rw (read/write) or
ro (read only) when mounting the volume (
rw is the default).
Managing Azure volumes
To create a volume that you can use in containers or Compose applications whenusing your ACI Docker context, you can use the
docker volume create command,and specify an Azure storage account name and the file share name:
By default, if the storage account does not already exist, this commandcreates a new storage account using the Standard LRS as a default SKU, and theresource group and location associated with your Docker ACI context.
If you specify an existing storage account, the command creates a newfile share in the existing account:
Alternatively, you can create an Azure storage account or a file share using the Azureportal, or the
You can also list volumes that are available for use in containers or Compose applications:
To delete a volume and the corresponding Azure file share, use the
volume rm command:
This permanently deletes the Azure file share and all its data.
When deleting a volume in Azure, the command checks whether the specified file shareis the only file share available in the storage account. If the storage account iscreated with the
docker volume create command,
docker volume rm alsodeletes the storage account when it does not have any file shares.If you are using a storage account created without the
docker volume create command(through Azure portal or with the
az command line for example),
docker volume rmdoes not delete the storage account, even when it has zero remaining file shares.
Run A Docker Container Locally
docker run, you can pass the environment variables to ACI containers using the
--env flag.For Compose applications, you can specify the environment variables in the Compose file with the
env-file service field, or with the
--environment command line flag.
You can specify a container health checks using either the
--healthcheck- prefixed flags with
docker run, or in a Compose file with the
healthcheck section of the service.
Health checks are converted to ACI
LivenessProbes. ACI runs the health check command periodically, and if it fails, the container will be terminated.
Health checks must be used in addition to restart policies to ensure the container is then restarted on termination. The default restart policy for
docker run is
no which will not restart the container. The default restart policy for Compose is
any which will always try restarting the service containers.
Example using Compose files:
Private Docker Hub images and using the Azure Container Registry
You can deploy private images to ACI that are hosted by any container registry. You need to log into the relevant registry using
docker login before running
docker run or
docker compose up. The Docker CLI will fetch your registry login for the deployed images and send the credentials along with the image deployment information to ACI.In the case of the Azure Container Registry, the command line will try to automatically log you into ACR from your Azure login. You don’t need to manually login to the ACR registry first, if your Azure login has access to the ACR.
Using ACI resource groups as namespaces
You can create several Docker contexts associated with ACI. Each context must be associated with a unique Azure resource group. This allows you to use Docker contexts as namespaces. You can switch between namespaces using
docker context use <CONTEXT>.
When you run the
docker ps command, it only lists containers in your current Docker context. There won’t be any contention in container names or Compose application names between two Docker contexts.
Install the Docker Compose CLI on Linux
The Docker Compose CLI adds support for running and managing containers on Azure Container Instances (ACI).
You can install the new CLI using the install script:
You can download the Docker ACI Integration CLI from thelatest release page.
You will then need to make it executable:
To enable using the local Docker Engine and to use existing Docker contexts, youmust have the existing Docker CLI as
com.docker.cli somewhere in your
PATH. You can do this by creating a symbolic link from the existing DockerCLI:
PATH environment variable is a colon-separated list ofdirectories with priority from left to right. You can view it using
echo $PATH. You can find the path to the existing Docker CLI using
which docker. You may need root permissions to make this link.
On a fresh install of Ubuntu 20.04 with Docker Enginealready installed:
You can verify that this is working by checking that the new CLI works with thedefault context:
To make this CLI with ACI integration your default Docker CLI, you must move itto a directory in your
PATH with higher priority than the existing Docker CLI.
Again, on a fresh Ubuntu 20.04:
After you have installed the Docker ACI Integration CLI, run
--help to see the current list of commands.
To remove the Docker Azure Integration CLI, you need to remove the binary you downloaded and
com.docker.cli from your
PATH. If you installed using the script, this can be done as follows:
Run A Docker Image Locally Windows
Thank you for trying out Docker Azure Integration. Your feedback is very important to us. Let us know your feedback by creating an issue in the compose-cli GitHub repository.