The Problem The docker engine package was upgraded. After that the user is not able to start the docker service, and revert back with error "docker dead but subsys locked" on verifying the status of the service. Under normal circumstances, the general solution would be to remove the lock file and the dead files of the service. This is not applicable in this condition. # rm /var/run/docker/execdriver/native/ # rm /var/lock/subsys/docker # docker info Cannot connect to the Docker daemon. Is … [Read more...] about “docker dead but subsys locked” – error while starting docker
DevOps
How to check the status and space used by images and containers
This post objective is to find out the stats of running container, system information related to space used by images and containers on /var/lib/docker. 1. 'docker stats' command used to check the containers stats on system like CPU usage, IO usage, Memory usage. Below example is for 2 running containers dockerweb and webserver2. # docker stats dockerweb webserver2 CONTAINER ID NAME CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS e33f00e0e3ce dockerweb … [Read more...] about How to check the status and space used by images and containers
6 Bash Shell Command Line Chaining Operators in Linux
Introduction In this article, I will explain you 6 Bash shell command line Chaining Operators (Linux operator). Now let’s discuss what is chaining operator. Chaining operator is something which helps to run multiple commands at once like we execute a script and task completes automatically. Usually, people use Bash shell command line Chaining Operators (Linux operator) in shell scripting but also we can use these operators on shell prompt. Here we are going to discuss on below Bash shell … [Read more...] about 6 Bash Shell Command Line Chaining Operators in Linux
What are Shell Scripts? How to Create Shell Scripts?
What Is a Shell? A shell is a program that provides an interface between a user and an operating system (OS) kernel. An OS starts a shell for each user when the user logs in or opens a terminal or console window. What Is a Shell Script? A shell script is a file that contains shell and UNIX commands. Similar to compiled executable programs, the shell script has a specific purpose and is reusable. When the commands in the shell script are ordered and error-free, you can execute the shell … [Read more...] about What are Shell Scripts? How to Create Shell Scripts?
How to backup and restore Docker containers
The post outlines the steps to take the backup (snapshot) of docker Container and restore it. Please note that this post mainly discusses committing a container as an image. This works on the container that does not use data volume. For containers with data volume, backup of the data volume must be taken separately. Taking backup of Docker Container 1. Commit the required container as an image # docker commit -p [container-id] backup01 sha256:89682d4xxxxxx Now a new image backup01 will … [Read more...] about How to backup and restore Docker containers
Run Docker as a non-root user
The Docker containers by default run with the root privilege and so does the application that runs inside the container. This is another major concern from the security perspective because hackers can gain root access to the Docker host by hacking the application running inside the container. Method 1 - Add user to Docker group 1. To run Docker as a non-root user, you have to add your user to the docker group. 2. Create a docker group if there isn't one: $ sudo groupadd docker 3. Add … [Read more...] about Run Docker as a non-root user
How to Configure Btrfs as the Storage Engine in Docker
Docker is an open platform management tool for Linux Containers. It provides a means for developers and system administrators to build and package applications into lightweight containers. Docker uses devicemapper devices as the default storage engine. To use Btrfs as the storage engine, perform the following steps. Note that Red Hat Enterprise Linux (RHEL) removes the Btrfs storage driver from their build of Docker, both on the Extra Packages for Enterprise Linux (EPEL) repository and the … [Read more...] about How to Configure Btrfs as the Storage Engine in Docker
How to create Docker Image from a Container and Dockerfile
Docker is an open platform management tool for Linux Containers. It provides a means for developers and system administrators to build and package applications into lightweight containers. Docker consists of the following components: Docker Engine – A portable, lightweight runtime and packaging tool Docker Hub – A cloud service for sharing applications and automating workflows Docker is used to create image-based application containers. Image-based containers package an application with … [Read more...] about How to create Docker Image from a Container and Dockerfile
Beginners Guide to The Docker World
Docker: Introduction Docker is an open platform management tool for Linux Containers. It provides a means for developers and system administrators to build and package applications into lightweight containers. Docker consists of the following components: Docker Engine – A portable, lightweight runtime and packaging tool Docker Hub – A cloud service for sharing applications and automating workflows Docker is used to create image-based application containers. Image-based containers … [Read more...] about Beginners Guide to The Docker World
Understanding Positional Parameters (Passing Parameters/Arguments to Shell script)
The execution of scripts is made versatile by the ability to run a script based on arguments supplied on the command line. In this way, the operation of the script varies depending on what arguments are given to the script. The shell automatically assigns special variable names, called positional parameters, to each argument supplied to a script on the command line. The positional parameter names and meanings are shown in Table below. Positional Parameter Name Returns true (0) if: $0The … [Read more...] about Understanding Positional Parameters (Passing Parameters/Arguments to Shell script)