How Do You Fix “Failed to start docker.service. Unit docker.socket is masked”?

Problem scenario
You try to start the Docker service (e.g., with sudo systemctl start docker). You get this error: “Failed to start docker.service. Unit docker.socket is masked”

What should you do?

Possible solution #1

sudo systemctl unmask docker.socket
sudo systemctl unmask docker.service

This solution was adapted from this blog.

Possible solution #2
Uninstall Docker.

How Do You Troubleshoot the Error “unable to prepare context…no such file or directory”?

Problem scenario
You run “docker-compose build” and you get this:

1 error occurred:
* unable to prepare context: unable to evaluate symlinks in Dockerfile path: lstat /home/jane/dockercompose/webapp/Dockerfile: no such file or directory

What should you do?

Solution
Look at your docker-compose.yml file. Look at the “build” stanza. What directory is it referring to? Is a Dockerfile file in that directory?

How Do You Create a docker.service File on a Linux Server?

One of the following apply:

Problem scenario #1
You run this: “sudo systemctl start docker”
But you get this: “Failed to start docker.service: Unit docker.service not found.”

Problem scenario #2
You run this: “sudo systemctl start docker”
But you get this:
“docker.service: Service has no ExecStart=, ExecStop=, or SuccessAction=. Refusing.”
or this:
“Failed to start docker.service: Unit docker.service not found.”

Problem scenario #3
You run this: sudo systemctl enable docker
But you get this: “Failed to enable unit: Unit file docker.service does not exist.”

Solution
Use this posting.

How Do You Solve “Error Problem with installed package …docker-ce conflicts with podman-docker”?

Problem scenario
You try to install docker-ce on a CentOS/Stream/RHEL/Fedora server, but you get an error like this:

Error:
Problem: problem with installed package podman-docker-1:3.4.1-3.module_el8.6.0+954+963caf36.noarch

package docker-ce conflicts with podmoan-docker

What should you do?

Solution
This will remove some packages. Do not do this if you have customized the packages involved.

Run these commands:

sudo yum remove buildah skopeo podman containers-common atomic-registries docker container-tools

sudo dnf -y install docker-ce …

Is It a Best/Recommended Practice to Run “sudo systemctl start docker”?

Problem scenario
You read that you should not run a Docker container as root or with sudo privileges. Can you start the docker service with sudo systemctl start docker?

Solution
Yes, it is acceptable. You can use this:

sudo systemctl start docker

This solution was taken from https://docs.docker.com/config/daemon/systemd/.

How Do You Get Chef to Be Automatically Installed and Configured (e.g., in a Docker Container)?

Problem scenario
You have a Docker container that supports Chef or some automatic way of installing Chef. The automation is failing at the end because you are being prompted to accept a license. What should you do to be able to invoke Chef commands automatically?

Solution
With the first Chef command, e.g., “chef env”, use the “–chef-license accept” option/flag. Here is an example:

chef env –chef-license accept

For more information,

Why Is There an Apparent Difference Between “docker run” and the Series of Two Commands “docker create” And “docker start”?

Problem scenario
When you run “docker run“, the container has a port that is exposed and the web application works properly.  When you use “docker create” then “docker start“, the service is not exposed properly. You believe that “docker run” the same as a series of two steps, first “docker create” then “docker start“.

How Do You Install the docker.service File on RHEL 8.x?

One of the following problems occurs:

Problem scenario #1
You run some systemctl commands to start the Docker service, but you get this error: “Failed to enable unit: Unit file docker.service does not exist.”
Or you run some other command and see this:
“Unit docker.service not found.”
What should you do to get the docker.service file on a RHEL 8.x server?

Problem scenario #2
You are running a kubeadm command on RHEL 8,

How Is Traffic Routed when a Browser Goes to a URL and the Website is Powered by a Kubernetes Cluster?

Question
You have been asked to explain how an external request for a website is routed and ultimately fulfilled by a pod in Kubernetes via an ingress controller. When a web browser downloads a website via HTTP and the website is running from a Kubernetes cluster, how does an individual container provide the HTML and/or data? How is external traffic routed to an underlying pod in a Kubernetes Cluster?