Editing Troubleshooting of docker errors

Troubleshooting of docker errors

== General Troubleshooting Steps of Docker Errors ==

=== Viewing Docker Logs ===
Enter the following command
<pre>
tail /home/dockerd.log
</pre>

Or the see the log of specific container ID
<pre>
docker logs <Container ID>

# OR enter the following command which the log was updated automatically
docker logs -f --details <Container ID>
</pre>

=== Useful Tools ===
* [https://hadolint.github.io/hadolint/ Dockerfile Linter]

== Common Error Solutions ==
=== Error: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?  ===
Error condition: After I inputted the command {{kbd | key = docker ps}}, I met the error message as follows:

<pre>
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running? 
</pre>

Solution: 
* On CentOS: {{kbd | key = sudo systemctl start docker}}<ref>[https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-on-centos-7 How To Install and Use Docker on CentOS 7 | DigitalOcean]</ref>



=== Error response from daemon: dial unix docker.raw.sock: connect: connection refused (on Mac) ===
Error condition: After I inputted the command {{kbd | key = docker ps}}, I met the error message as follows:

<pre>
Error response from daemon: dial unix docker.raw.sock: connect: connection refused
</pre>

Solution: Make sure the docker is running. After docker was lunched, the result of command {{kbd | key = docker ps}} should be:
<pre>
CONTAINER ID   IMAGE     COMMAND   CREATED   STATUS    PORTS     NAMES
</pre>

=== Error response from docker desktop: credential when tried to docker push ===

Solution: Login the account of docker hub

=== Error response from docker desktop: denied: requested access to the resource is denied when tried to docker push ===

Solution: Add tag to the docker image you want to publish<ref>[https://stackoverflow.com/questions/43858398/docker-push-error-denied-requested-access-to-the-resource-is-denied docker push error "denied: requested access to the resource is denied" - Stack Overflow]</ref> 

<pre>
docker tag <IMAGE ID> <ACCOUNT NAME>/<NAME>:<TAG>
</pre>

=== .:/app bind mount allows container to write back to host ===
Error condition: The <code>.:/app</code> entry in {{kbd|key=docker-compose.yml}} defaults to read-write, meaning processes inside the container can write back to the entire project directory on the host — including <code>.env</code> files containing API keys. If the Streamlit app has a vulnerability that gets exploited, an attacker could use the container to modify arbitrary files on the host.

Solution: In the <code>volumes</code> section of <code>docker-compose.yml</code>, append <code>:ro</code> (read-only) to the code directory, and keep only the <code>data</code> directory as read-write:

<pre>
volumes:
  - .:/app:ro              # source code read-only
  - ./data:/app/data       # data directory remains read-write
  - ./.env:/app/.env:ro
</pre>

If the Streamlit app needs to write temporary files outside of <code>/app</code>, grant write access to that specific subdirectory individually — do not remove the top-level <code>:ro</code>.

=== docker group membership not taking effect — docker ps still shows permission denied ===
Error condition: After running {{kbd|key=sudo usermod -aG docker your-username}}, subsequent {{kbd|key=docker ps}} still shows the following error:

<pre>
permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock
</pre>

Cause: The current SSH session was established before <code>usermod</code> ran. Group membership changes do not apply to existing sessions.

Solution:
* Confirm the account has been added to the <code>docker</code> group: {{kbd|key=groups your-username}} — output should include <code>docker</code>
* Fully log out of SSH and reconnect: {{kbd|key=exit}}
* After reconnecting, verify with {{kbd|key=groups}} (should include <code>docker</code>) and {{kbd|key=docker ps}} (should list containers normally)

Note: On certain Debian environments, <code>newgrp docker</code> may return <code>Invalid password</code> and refuse to execute even when no password is expected — this is known behaviour. A full SSH reconnect is the correct fix.

=== Error: This image might run with root as the default user. Make sure it is safe here. ===
[[Troubleshooting_of_SonarQube_issue#How_to_resolve_"This_image_might_run_with_root_as_the_default_user._Make_sure_it_is_safe_here." | This image might run with root as the default user. Make sure it is safe here]]

== References ==
<references />

{{Template:Troubleshooting}}

[[Category: Programming]]
[[Category: Docker]]