Docker Overview Flashcards
What are containers?
- Containers are completely isolated environments, they can have their own processes or services, their own network interfaces, their own mounts, just like virtual machines. Except that they all share the same OS kernel.
Can you show an illustration of how containers sit and interact with OS?
Most important to remember about docker?
Docker container share the underlying OS kernel
Docker can run any flavor of OS on top of it as long as all are based on the same base OS kernel.
For eg if there is ubuntu os, and docker installed on top of it, it can run other OSes which are based on the same Linux OS kernel
Can we run a windows container here in this case ?
No,Docker can run any flavor of OS on top of it as long as all are based on the same kernel. In this case Underlying OS is ubuntu, which is linux kernel. so all linux kernel based OS can run on top of the container
What is main purpose of Docker?
Package and containerize applications, and to ship them, and to run them anywhere anytime as many times as you want
Docker vs virtualization Differences
One disadvantage of docker over virtualization?
Dockers are not completely isolated, in the sense that underlying OS kernel is shared. You can only run those OS kernel based OSs on top of the container.
Hypervisors are opposite can run any OS, and have their own reserved hardware spec.
It is usually not Containers vs Virtualization but instead it is using both Contiainers and Virtualization more effectively
in case of Docker, we have the underlying
hardware infrastructure, and then the OS, and
then Docker installed on the OS. Docker then manages the containers that run with libraries and dependencies alone. In case of virtual machines, we have the hypervisor like ESX
on the hardware and then the virtual machines
on them. As you can see, each virtual machine
has its own OS inside it, then the dependencies, and then the application.
The overhead causes higher utilization of
underlying resources, as there are multiple virtual
operating systems and kernels running. The
virtual machines also consume higher disk space
as each VM is heavy and is usually in gigabytes
in size, whereas Docker containers are lightweight and are usually in megabytes in size. This allows
Docker containers to boot up faster, usually, in a matter of seconds, whereas VMS, as we know, takes minutes to boot up as it needs
to boot up the entire operating system. It is also important to note that Docker has less isolation as more resources are shared between
the containers like the kernel, whereas VMS have
complete isolation from each other. Since VMS
don’t rely on the underlying OS or kernel,
you can run different types of applications built
on different OSS such as Linux-based or
Windows-based apps on the same hypervisor.
What is docker Hub or Docker store?
Most of the companies have their products containerised now a days and are available for download from docker hub or docker store
What is a docker image?
An image is a package or a template, just like a VM template that you might have worked with in the virtualization world, it is used to create one or more containers.
A lot of products have been dockerized already, incase you don’t find, you can create your own image
What are docker containers?
Containers are running instances of images that are isolated and have their own environments and set of processes.
What can docker containers do?
