- Docker is a set of platform as a service products that use OS-level virtualization to deliver software in packages called containers. Containers are isolated from one another and bundle their own software, libraries and configuration files; they can communicate with each other through well-defined channels. All containers are run by a single operating-system kernel and are thus more lightweight than virtual machines. Containers are created from images that specify their precise contents. Images are often created by combining and modifying standard images downloaded from public repositories.
to solve the compatibility issue between different operating systems and different versions of the same operating system and different environments and different versions of the same environment
Docker is a tool designed to make it easier to create, deploy, and run applications by using containers. Containers allow a developer to package up an application with all of the parts it needs, such as libraries and other dependencies, and ship it all out as one package. By doing so, the developer can rest assured that the application will run on any other Linux machine regardless of any customized settings that machine might have that could differ from the machine used for writing and testing the code.
- with docker you can run each service in a separate container with its own dependancies and libraries ,and each container will have its own IP address and port number. This means that you can run multiple instances of the same service on the same server without any conflicts. This is a huge advantage over running multiple instances of the same service on the same server using virtual machines.
container is completely isolated environment for running applications and each container has its own process space, network interface, and filesystem. Containers are lightweight because they don’t need the extra load of a hypervisor, but they all share the os kernel. This means they require less memory than virtual machines (VMs). Containers are also more portable and efficient. You can build images locally, store them in a private registry, and deploy them to any infrastructure that supports Docker containers.
A container is a standard unit of software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another. A Docker container image is a lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries and settings.
- An image is a read-only template with instructions for creating a Docker container. A container is a runnable instance of an image. You can create, start, stop, move, or delete a container using the Docker API or CLI. You can commit your container’s changes into a new image using the Docker commit command. You can push and pull images from Docker registries.
1- Run or start a container
docker run 'image name'1.1- Run a version of an image
docker run 'image name':'tag' # if you don't specify the tag then the latest version will be used ny default1.2- Run STDIN
docker run -i 'image name' # this command will run the container and will allow you to execute commands inside the containerdocker run -it 'image name' # this command will run the container and will allow you to execute commands inside the container and will attach to the container1.3- Append a command
docker run 'image name' 'command'1.4- Run a container in the background
docker run -d 'image name'1.5- Run a container in the foreground
docker run -it 'image name' # this command will run the container and execute the command inside the container1.6- Run a container in the foreground and attach to it
docker attach 'container id/name' # this command will attach to a running container and will allow you to execute commands inside the container1.7- Run - PORT MAPPING
docker run -p 'host port':'container port' 'image name' # this command will run the container and will map the container port to the host port to allow the host to access the container port from outside the container1.8- Run - VOLUME MAPPING
docker run -v 'host path':'container path' 'image name'
1.9 - set environment variables
docker run -e 'environment variable name'='environment variable value' 'image name'1.10 - set environment variables from a file
docker run --env-file 'environment variables file path' 'image name'1.11 - inspect environment variables
docker inspect 'container id/name' # this command will return the container details that contains the environment variables in a json format
2- List containers
docker ps2.1- List all containers
docker ps -a2.2- List images
docker images
docker stop 'container id/name'
docker rm 'container id/name'
docker rmi 'image id/name' # but you have to make sure that the image is not used by any container
docker pull 'image name' # also the image will be downloaded automatically when you run a container if the image is not already downloaded
docker exec 'container id/name' 'command' # this command will run the container in the background and will return the container id
docker inspect 'container id/name' # this command will return the container details in a json format
docker logs 'container id/name'
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Docker file is a text written in a specific format that docker can understand and use it to build an image
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evert thing in the left in capital letters is a command or an instruction each instruction makes docker perform a specific task
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A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image. Using docker build users can create an automated build that executes several command-line instructions in succession.
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when you were buiding an image you were actually running a series of commands that were written in the docker file
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while building the image if any failure happens the image will not be created but docker will cache the previous steps/layers until the failure step and will not run the steps after the failure step
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when the faulure step is fixed and the image is built again docker will not run the steps that were already run before the failure step and will use the cached layers and run the failed step then the steps after the failure
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Docker networks are the virtual networks that are used to connect the containers together
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Docker networks are isolated from each other and they are not connected to the host network
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Docker networks are created using the docker network command
docker network create 'network name' -
Docker networks can be created in 3 different modes
- Bridge: the default mode
- Host : the host network
- None : no network
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Docker networks can be connected to each other using the docker network connect command
docker network connect 'network name' 'container name' -
Docker networks can be disconnected from each other using the docker network disconnect command
docker network disconnect 'network name' 'container name' -
Docker networks can be removed using the docker network rm command
docker network rm 'network name' -
Docker networks can be listed using the docker network ls command
docker network ls -
Docker networks can be inspected using the docker network inspect command
docker network inspect 'network name'
each operating system consists of OS Kernel and a set of applications and libraries that are used to run the operating system
the os kernel is the core of the operating system and it is responsible for managing the hardware resources and the applications and libraries that are used to run the operating system
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