Java stores certificates in keystore files.
For example, the trusted CA certificates, by default, are stored in $JAVA_HOME/jre/lib/security/cacerts file.
The certificates in a Java keystore file can be listed using the keytool -list command and in this short note i will show how to. (more…)
A Context in Kubernetes is used to group access parameters under convenient names in a kubeconfig file.
Each Context has three parameters: Cluster, Namespace and User.
In this note i will show how to display and how to change Context in Kubernetes using the kubectl command. (more…)
A Pod is a group of one or more containers with shared storage, network and lifecycle and is the basic deployable unit in Kubernetes.
Each Pod is scheduled on the same Node, and remains there until termination or deletion.
In case of a Node failure, identical Pods are scheduled on other available Nodes in the cluster.
In this note i will show how to list Pods in Kubernetes cluster and how to get detailed information about them using the kubectl command. (more…)
Kubernetes supports multiple virtual clusters backed by the same physical cluster.
These virtual clusters in Kubernetes are called Namespaces.
The Namespaces allow to partition physical resources into the logically named groups, allowing a Kubernetes cluster to share resources between multiple groups.
In this note i will show how get the current Namespace and how to list all Namespaces in Kubernetes cluster using the kubectl command. (more…)
A Node in Kubernetes is a worker machine (virtual or physical), managed by the control plane.
Each Node contains the services necessary to run Pods: docker, kubelet and kube-proxy.
This guide describes how list Nodes in Kubernetes and how to get extended information about them using the kubectl command. (more…)
Sometimes it is required to check the current version of Java installed.
By Java version i mean the version of Java Development Kit (JDK) or the version of Java Runtime Environment (JRE).
As JDK and JRE are different components of Java (JDK is used to compile Java programs while JRE is used to run them), there are different commands to check their versions.
This short note explains how to find out the current version of Java (JDK/JRE) from the command line. (more…)
Sometimes it is required to run an application as a different user.
For example, you may want to run an elevated command prompt to execute some commands with administrative privileges.
In Windows, an executable file can be run as a different user from the File Explorer or using the command line. (more…)
To start using a private Docker Registry a user usually should run the docker login command and set a username and password that will be cached locally.
If a user tries to docker pull or docker push an image from/to a private Docker Registry, without having run the docker login command in advance, he may receive the “unauthorized: authentication required” error.
This guide explains how to log in and how to log out of a private Docker Registry from the command line using the docker login and docker logout commands. (more…)
Multiple commands can be executed in a running Docker container using the docker exec command.
If the Docker container is stopped, before running the docker exec command it should be started using the docker run command.
In this short note i will show the examples of how to execute multiple commands in a Docker container. (more…)
The docker exec command serves for executing commands in a running container.
If the Docker container is stopped, before running the docker exec command it should be started using the docker run command.
In this short note i will show the examples of how to execute commands Docker containers. (more…)