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Containers in Linux .


 The term container and the concept came from the shipping container . 

These container are shipped from city to city and country to country . 
No matter which part of the world you go , you will always find these containers with the exact same measurements because around the world  all docks , trucks ,ships and warehouse are built to easily transport and store them . 



> Now consider the situation , developers create the application and that application is working fine in their laptop , but when the application is moved to the production environment , application is not running . The most basic reason is change of the architecture . 


> Then comes the container technology which allows developers or programmer to test and build applications on any computerr just by putting it in the container and then run on another computer regardlesss of its architechture . 

>you can move the application anywhere without moving its OS just like moving actual container anywhere that would fit on any truck , ship or warehouse . 


> Note : Containers are mostly used by developers and programmers who writes the code and build the application . As a system admin your job is to install , configure and manage them . 

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Question :  what are the container softwares ? 

Docker :  docker is the software used to create and manage the containers . 
Just like the other package, docker can be installed on your linux system and its service or daemon can be controlled through native Linux service management tool . 


Podman :

Podman is alternative to Docker . 
Docker is not supported in RHEL 8 . 

It is the daemon less , open source , Linux - native tool designed to develop, manage and run containers . 


>Redhat provides set of command line tools that can operate without a container engine , these includes : 

podman :  for directly managing pods and container images (run, stop,start , ps attach, etc).

buildah : for building pushing and signing container images . 

skopeo : for copying , inspecting ,deleting and signing images . 

runc : for providing container run  and build features to podman and buildah . 

crun : an optional runtime that can be configured  and give greater flexibility ,control and security for rootless containers . 


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images  :  containers can be created  through images and containers can be converted to images . 


pods : groups of containers deployed together on the host. In the podman logo there are 3 seals grouped together as pod . 


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Building running and managing the containers : 


To install podman : 

#yum/dnf  install podman -y 


To install docker : 

#yum install docker -y 


creating alias to docker : 
#alias   docker=podman


check podman version : 

#podman  -v 


getting help : 

#podman   --help    or    man podman 


check podman environment and registry /repository information : 

#podman   info  



to search for specific image in the repository : 
#podman  search  httpd 




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