A Technical I.T./DevOps Blog
Problem scenario
You run a docker command, but you get “port bindings are not yet supported by rootless containers”. What should you do?
Solution
Use sudo before the Docker command.
Waning: The above is not recommend for security purposes. Only follow this direction (with sudo docker run…), if the server is not that important or you are in a very secure network.
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Problem scenario
How do you resolve the Docker error ‘ERRO[0000] cannot setup namespace using newuidmap: exit status 1’?
Possible Solution #1
Reboot the Docker host.
Possible Solution #2
Good commands to help understand what might be going on are lsns, sudo lsns, and man nsenter
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Problem scenario
You wrote a Dockerfile. You are using it to try to create a Docker image. When you run the “docker build” command you get some error messages. The errors include one or more of the following:
1) A MarkupSafe fatal error related to Python.h.
2) A C extension not being compiled.
3) An invalid syntax error related to async (e.g., “Jinja2/jinja2/asyncfilters.py”).
You need to base the image off Ubuntu.
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Problem scenario
Docker Hub is a public registry for containers. Does OpenShift support something like this? You know they have the OpenShift Container Registry — but this is private to a given OpenShift instance. Red Hat owns OpenShift. Is there a public registry supported by Red Hat?
Answer
Yes. It is called Quay.io. If you want a brief overview of it,
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Continue reading “Is there a Docker Hub equivalent for OpenShift?”
Question
In Docker what are possible status values of containers?
Answer
Possible statuses include the following:
created, restarting, running, removing, paused, up, exited, or dead
Sources: 1) https://docs.docker.com/engine/reference/commandline/ps/ (for every one except “up”)
2) https://www.thegeekdiary.com/how-to-list-start-stop-delete-docker-containers/ (for “up”)
The docker create command when used with a Docker image ID will produce a new container in the “Created” state.
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Continue reading “What Are The Different Statuses of Individual Docker Containers?”
Problem scenario
You run a command like this: docker build -t “ricepaper:contint”
But you receive a message such as this:
Emulate Docker CLI using podman. Create /etc/containers/nodocker to quiet msg.
no context directory specified, and no dockerfile specified
How do you resolve this problem?
Solution
Use a space and a period at the end of the command.
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Problem scenario
You want to bypass Docker and configure the cgroups directly. You want new Docker containers to be governed by these customized settings. What should you do?
Solution
You may not want to bypass Docker for your cgroup modifications. You should read about the libcontainers. By default Docker uses libcontainers for granular configuration changes along the lines of modifying cgroups settings.
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Question
You have noticed that Docker and Jenkins are regularly used together. Why is this?
Answer
1. The docker build command produces one artifact. Jenkins lends itself to well-defined tasks.
2. The logic and dependencies of the build can usually be completely contained in the Dockerfile (page 20 of Docker Up and Running). Simple lines of text can standardize many aspects of a given build (e.g.,
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Problem scenario
You want to deploy the Spring framework with Docker. How do you do this?
Solution
Warning: The last step in this is not a security “recommended practice.” Only follow these directions (with sudo docker run…), if the server is not that important or you are in a very secure network. One published book says you can use “sudo docker …” as long as the server is not in production (page 43 of Docker Up and Running).
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Continue reading “How Do You Install Spring Framework with Docker?”
Problem scenario
You want to use the Docker Pipline (with the Jenkins ID of “docker-workflow”). What do you do?
Solution
Prerequisites
Jenkins needs to be installed. If you need assistance, see this posting if you are using a CentOS/RHEL/Fedora server; if you want to install Jenkins on a Debian/Ubuntu server, see this posting.
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Continue reading “How Do You Use the Docker Pipeline Plugin with Jenkins?”