Dealing with volumes

Goal

This project is about volumes. You will:

start the demo application with different volume types
get to know the differences between managed volumes and bind mounts

Tools

Try to complete the tasks below with the help of the slides and the cheatsheet.
If you have any problems, you will find a fold-out block for each task describing the solution.

Preparation

Create a folder volumes as a subfolder of the workspace folder.

Solution (click on the arrow if you get stuck)

If the Explorer bar of VSCode is not already displayed on the left, open Explorer of VSCode with Ctrl + B or alternatively by clicking on the file icon (above the magnifying glass) in the left bar.
Make sure that you are in the workspace folder.
Create a new folder with the name volumes via the Explorer.
- Alternatively in the terminal: mkdir volumes. Again, make sure that you are in the workspace folder.

Change to the volumes folder in the terminal.

Solution (click on the arrow if you get stuck)

(Optional) Open a terminal (Menu > Terminal > New Terminal).
Change to the created folder with cd volumes. If you are still in the docker-demoapp folder from the last task, you must first go up one folder level with cd .. and then enter cd volumes.
Execute pwd. pwd returns the current directory. You should get the output /home/coder/workspace/volumes.
If you do not receive the output, change to the directory with cd /home/coder/workspace/volumes.

Task 1 - Bind Mounts

1.1: Create bind mount

Make sure that you are in the directory /home/coder/workspace/volumes.
Start the demo application with the following properties:
- in the background
- with port forwarding (8080 -> 5000)
- a bind mount
  - Host path: ${PWD}/data
  - Container path: /app/data/notes
- Note that the files are not mounted in read-only mode

Solution (click on the arrow if you get stuck)

Create the folder data with mkdir data and start the image with the following command:

docker run -d -p 8080:5000 --mount type=bind,source=${PWD}/data,target=/app/data/notes corewire/docker-demoapp

1.2: Check demo application

Visit the demo application in the browser. It can be reached via your URL (code-{NUMBER}.labs.corewire.de) on port 8080. Use http:// and not https://.
Enter 1-2 notes.

Solution (click on the arrow if you get stuck)

Try to open the webapp in a new tab under http://code-0.labs.corewire.de:8080/.
Important:
- http not https
- Replace code-0 with your instance.

1.3: Check bind mount on the host

In the Explorer in VSCode you will see the folder volumes/data. Check the contents.
The folder contains your notes. These are persisted on the host system by the bind mount.
Edit a note and save the file.
Reload the demo application in the other tab with F5.
You should see your modified note.

You have successfully created a bind mount in task 1. The notes, i.e. the state of the container, are now saved independently of the container itself. This means that the container can now be started, stopped and deleted at will without losing the data. the data being lost.

In the following, we now want to start a second container that accesses the same directory.

2.1: Starting another demo application

Make sure that you are in the directory /home/coder/workspace/volumes.
Start the demo application with the following properties:
- in the background
- with port forwarding (8081 -> 5000). Important: Port 8080 is already assigned.
- a bind mount
  - Host path: ${PWD}/data.
  - Container path: /app/data/notes
  - Mode: Readonly

Solution (click on the arrow if you get stuck)

Start the image with the following command:

docker run -d -p 8081:5000 --mount type=bind,source=${PWD}/data,target=/app/data/notes,readonly corewire/docker-demoapp

2.2: Check demo application

Visit the demo application in a new tab.
It contains the same notes as the demo application on port 8080.

2.3: Creating a note

Try to create a note on the demo application on port 8081.
You should receive an error because the application does not have write access to the directory.
Create a note in the demo application on port 8080.
Reload both demo applications.

2.4: Stop demo application

Stop both demo applications.

VSCode Container

The containers code-server and vscode-traefik provide the VSCode program. Do not stop these containers, otherwise the instance will no longer be accessible.

Solution (click on the arrow if you get stuck)

Execute the following command to display the running containers:
```
docker ps
```
Search for the entries with corewire/docker-demoapp in the IMAGE column.
Copy either the CONTAINER ID at the beginning of the line or the NAME at the end of the line.
Stop both containers individually with :
```
docker stop <ID or name>
```

Task 3 - Managed Volumes

In the following, we want to implement the same scenario with Managed Volumes.

3.1: Starting the demo application with Managed Volumes

Start the demo application with the following properties:
- in the background
- with port forwarding (8080 -> 5000)
- a managed volume
  - Volume name: demoapp_notes.
  - Container path: /app/data/notes

Solution (click on the arrow if you get stuck)

Create the volume and start the image with the following command:

docker volume create demoapp_notes
docker run -d -p 8080:5000 --mount source=demoapp_notes,target=/app/data/notes corewire/docker-demoapp

3.2: Check demo application

Visit the demo application in a new tab.
Write 1-2 notes.

3.3: Display volume

Display all volumes. You should get a comparable output:

DRIVER VOLUME NAME
local demoapp_notes

Solution (click on the arrow if you get stuck)

Display all volumes with the following command:
```
docker volume ls
```

Now also display the low-level details of the volume. These contain, for example, the mountpoint under /var/lib/docker.

Solution (click on the arrow if you get stuck)

Display the details with the following command:
```
docker volume inspect demoapp_notes
```

3.4: Start another demo application

Start the second demo application with the following properties:
- in the background
- with port forwarding (8081 -> 5000). Important: Port 8080 is already assigned.
- a managed volume
  - Volume name: demoapp_notes.
  - Container path: /app/data/notes
  - Mode: Readonly

Solution (click on the arrow if you get stuck)

Start the image with the following command:

docker run -d -p 8081:5000 --mount source=demoapp_notes,target=/app/data/notes,readonly corewire/docker-demoapp

3.5: Check demo application

Visit both demo applications.
Try to create notes in both demo applications.
The behavior should be the same as before:
- Demo application 1 can create new notes.
- Demo application 2 can only display the notes.

3.6: Stop demo application

As before, stop both demo applications.

VSCode Container

The containers code-server and vscode-traefik provide the VSCode program. Do not stop these containers, otherwise the instance will no longer be accessible.

Solution (click on the arrow if you get stuck)

Execute the following command to display the running containers:
```
docker ps
```
Search for the entries with corewire/docker-demoapp in the IMAGE column.
Copy either the CONTAINER ID at the beginning of the line or the NAME at the end of the line.
Stop both containers individually with :
```
docker stop <ID or name>
```

Dealing with volumes

Preparation

Task 1 - Bind Mounts

1.1: Create bind mount

1.2: Check demo application

1.3: Check bind mount on the host

Task 2 - Share bind mounts

2.1: Starting another demo application

2.2: Check demo application

2.3: Creating a note

2.4: Stop demo application

Task 3 - Managed Volumes

3.1: Starting the demo application with Managed Volumes

3.2: Check demo application

3.3: Display volume

3.4: Start another demo application

3.5: Check demo application

3.6: Stop demo application