Configuring data output from a Docker container to a serial port

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Updated at April 12, 2024

Prepare your cloud
- Required paid resources
Create a VM specification file
Create a Docker container specification file
Get the ID of the image to create the VM
Create a VM
Check the result
How to delete the resources you created

To create a VM from an image, such as a Container Optimized Image, and set up a redirect of the application output stream to the VM's serial port:

If you no longer need the resources you created, delete them.

Prepare your cloud

If the required Docker image is pushed to Container Registry, create a service account with the container-registry.images.puller role for the registry in use. A Container Optimized Image VM will pull the Docker image from the registry on behalf of this account.

If you do not have the Yandex Cloud command line interface yet, install and initialize it.

The folder specified in the CLI profile is used by default. You can specify a different folder using the --folder-name or --folder-id parameter.

If you don't have a network or subnet, create them.

Required paid resources

The infrastructure support cost includes:

Fee for a continuously running VM (see Yandex Compute Cloud pricing).
Fee for using a dynamic or static external IP address (see Yandex Virtual Private Cloud pricing).

Create a VM specification file

CLI

Create a VM specification file named cloud-config-ports.yaml and populate it with the following data:

#cloud-config
runcmd:
- [ sudo, chmod, 666, /dev/ttyS1]
users:
- name: <username>
  groups: sudo
  shell: /bin/bash
  sudo: 'ALL=(ALL) NOPASSWD:ALL'
  ssh-authorized-keys:
  - <public_SSH_key_to_connect_to_VM>

In the file configuration, set the username and specify the public part of the SSH key required to connect to the VM. You need to create an SSH key pair yourself.

Create a Docker container specification file

CLI

Create a specification for a Docker container as a file named container-spec-ports.yaml and populate it with the following data:

spec:
containers:
- image: ubuntu
  name: app
  command: ["/bin/bash", "-c", "sleep 30 && echo 'Hello World!' > /dev/ttyS1"]
  securityContext:
    privileged: true
    stdin: false
    tty: false
    volumeMounts:
    - mountPath: /dev/ttyS1
      name: log-port
  restartPolicy: Always
  volumes:
  - name: log-port
    hostPath:
      path: /dev/ttyS1

Create a VM with multiple disks.
1. Get the ID of the image to create the VM:
  Bash
  
  PowerShell
  IMAGE_ID=$(yc compute image get-latest-from-family container-optimized-image --folder-id standard-images --format=json | jq -r .id)
  > $IMAGE_ID=(yc compute image get-latest-from-family container-optimized-image --folder-id standard-images --format=json | ConvertFrom-Json).id
2. Create a VM:
```
yc compute instance create \
  --name coi-vm-with-sp \
  --zone ru-central1-a \
  --network-interface subnet-name=<subnet_name>,nat-ip-version=ipv4 \
  --metadata-from-file user-data=cloud-config-ports.yaml,docker-container-declaration=container-spec-ports.yaml \
  --create-boot-disk image-id=$IMAGE_ID
```
  Where:
  - --name: VM name.
  - --zone: Availability zone.
  - --network-interface: VM network settings.
  - --metadata-from-file: YAML metadata files to create the VM.
  - --create-boot-disk: ID of the image to create a boot disk from.
  Once created, the VM will appear in the VM list under Compute Cloud in the management console.
3. Check the result.
  1. In the management console, go to the folder page and select Compute Cloud.
  2. Click the name of the coi-vm-with-sp VM.
  3. Under Serial port, select COM2. In a few minutes, the screen will display Hello world!.

Get the ID of the image to create the VM

To get the ID of the latest image used for VM creation, run:

Linux (Bash)

Windows (PowerShell)

IMAGE_ID=$(yc compute image get-latest-from-family container-optimized-image \
  --folder-id standard-images \
  --format=json | jq -r .id)

$IMAGE_ID=(yc compute image get-latest-from-family container-optimized-image `
  --folder-id standard-images `
  --format=json | ConvertFrom-Json).id

Create a VM

CLI

Enter a name for the subnet to create your VM in and run:

yc compute instance create \
  --name coi-vm-with-sp \
  --zone ru-central1-d \
  --network-interface subnet-name=<subnet_name>,nat-ip-version=ipv4 \
  --metadata-from-file user-data=cloud-config-ports.yaml,docker-container-declaration=container-spec-ports.yaml \
  --create-boot-disk image-id=$IMAGE_ID

Where:

--name: VM name.
--zone: Availability zone.
--network-interface: VM network settings.
--metadata-from-file: YAML metadata files to create the VM.
--create-boot-disk: ID of the image to create a boot disk from.

Once created, the VM will appear in the VM list under Compute Cloud in the management console.

Check the result

To check the result of configuring data output from the Docker container to the serial port:

In the management console, go to the folder page and select Compute Cloud.
Click the name of the coi-vm-with-sp VM.
Under Serial port, select COM2. In a few minutes, the screen will display Hello world!.

For more information about working with VMs, see our step-by-step guides.

How to delete the resources you created

To stop paying for the resources you created:

Delete a VM.
If you reserved a public static IP address for the VM, delete it.

Configuring data output from a Docker container to a serial port

Prepare your cloudPrepare your cloud

Required paid resourcesRequired paid resources

Create a VM specification fileCreate a VM specification file

Create a Docker container specification fileCreate a Docker container specification file

Get the ID of the image to create the VMGet the ID of the image to create the VM

Create a VMCreate a VM

Check the resultCheck the result

How to delete the resources you createdHow to delete the resources you created

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