72 lines
1.9 KiB
Markdown
72 lines
1.9 KiB
Markdown
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## Run, Forest, Run!
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### Objective
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Learn what restart policies do and how to use them
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### Requirements
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Make sure Docker is installed on your system and the service is started
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```
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# Fedora/RHEL/CentOS
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rpm -qa | grep docker
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systemctl status docker
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```
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### Instructions
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1. Run a container with the following properties:
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* image: alpine
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* name: forest
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* restart policy: always
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* command to execute: sleep 15
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`docker run --restart always --name forest alpine sleep 15`
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2. Run `docker container ls` - Is the container running? What about after 15 seconds, is it still running? why?
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It runs even after it completes to run `sleep 15` because the restart policy is "always". This means that Docker will keep restarting the **same** container even after it exists.
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3. How then can we stop the container from running?
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The restart policy doesn't apply when the container is stopped with the command `docker container stop`
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4. Remove the container you've created
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```
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docker container stop forest
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docker container rm forest
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```
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5. Run the same container again but this time with `sleep 600` and verify it runs
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```
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docker run --restart always --name forest alpine sleep 600
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docker container ls
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```
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6. Restart the Docker service. Is the container still running? why?
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```
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sudo systemctl restart docker
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```
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Yes, it's still running due to the restart policy `always` which means Docker will always bring up the container after it exists or stopped (not with the stop command).
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8. Update the policy to `unless-stopped`
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`docker update --restart unless-stopped forest`
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9. Stop the container
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`docker container stop forest`
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10. Restart the Docker service. Is the container running? why?
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```
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sudo systemctl restart docker
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```
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No, the container is not running. This is because we changed the policy to `unless-stopped` which will run the container unless it was in stopped status. Since before the restart we stopped the container, Docker didn't continue running it after the restart.
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