Docker Container Introduction
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This document discusses Docker containers and provides an introduction. It begins with an overview of Docker and how it uses containerization technology like Linux containers and namespaces to provide isolation. It describes how Docker images are composed of layers and how containers run from these images. The document then explains benefits of Docker like portability and ease of scaling. It provides details on Docker architecture and components like images, registries and containers. Finally, it demonstrates how to simply run a Docker container with a command.
Docker Container Introduction
- 2. Personal Profile: ● Payam Naderi ● Fullstack Developer at Innfinision Cloud Solutions ● [email protected] ● Innfinision.net
- 3. innfinision Cloud Solutions: ● Providing Cloud, Virtualization and Data Center Solutions ● Developing Software for Cloud Environments ● Providing Services to Telecom, Education, Broadcasting & Health Fields ● Supporting OpenStack Foundation as the First Iranian Company ● First Supporter of IRAN OpenStack Community
- 4. Docker Container Introduction innfinision.net ● Preface ● Linux Containers Preface ● Linux Container Concepts ● LXC Copy On Write Filesystem ● Docker Preface ● Introduction Container Image ● Why Docker ● Docker Architecture Agenda: ● Docker Architect, How Working ● Underlying Technology ● Immutable infrastructure with Docker
- 6. Virtualization / Containerization innfinision.net How changed the data center and cloud forever ● More Agile ● Manageable ● Cloud Friendly ● Application Friendly The Containerization technology is seeing resurgence with Docker. Docker has revived the interest of the technology community in containers. Docker Container Introduction
- 7. Fundamental Containerization Support innfinision.net Containerization was actually included in the Linux 2.6.24 called LXC. Linux Container (LXC) ● Provide System-Level Virtualization ● Allow Single Host to Operate Multiple Isolated Linux Instances. ● Based on Linux cGroup LXC Make Complete App. Isolation ● Linux cGroup Offer Complete App Isolation include Process, Memory, IO ● Namespaces Offer Filesystem, UserID, NetworkID, GroupID ... Docker Container Introduction
- 8. Docker Uses Container Technology innfinision.net Docker uses the container technology but creates a layer above the LXC. Use Containers for ● Packaging ● Deployment ● Migration of Workload to different hosts. Docker is well suited for Clouds ● Reducing the datacenter footprint and using the host’s resources to their maximum using the Docker and LXC technology. ● Ease of migration and fast scale out of containers. Docker Container Introduction
- 9. Linux Containers Preface innfinision.netDocker Container Introduction
- 10. Virtualization OS innfinision.net Refers to the creation of virtual machines which have an independent operating systems but the execution of software running on the virtual machine is separated from the underlying hardware resources. Docker Container Introduction
- 11. Virtualization OS innfinision.net Naming VM. Elements ● Host Machine: The actual machine that runs the virtualization software ● Guest Machine: The virtual machine running on top of the virtualization software. ● Virtual Machine Manager or a Hypervisor: The software that provides virtualization capabilities and abstracts the hardware. Docker Container Introduction
- 12. Virtualization Vs Containerization innfinision.net Linux containers have a different approach than virtualization; you may call it an OS level virtualization. Container Virtualization ● Fully Isolated OS on Same Host Kernel ● Containers isolate the guest but do not virtualize the hardware ● Limited to a single operating system, thus you cannot run Linux and windows together ● Work on the Concept of Process Level Virtualization Docker Container Introduction
- 14. Linux Container innfinision.netDocker Container Introduction
- 15. Linux Container innfinision.net Docker works on a technology called Linux containers. There are two main concepts involved within Linux Containers, Namespaces Cgroups (Control groups.) Docker Container Introduction
- 16. Namespaces innfinision.net ● Offer process level isolation for Linux resources. ● Ensure that each container sees only its own environment and doesn’t affect or get access to processes running inside other containers. Docker Container Introduction
- 17. Different Kinds of Namespaces innfinision.net ● PID: Considered as most important isolation factor in containers. ● NET: Controlling the networks and net interfaces. ● MNT: Isolates the file system mount points. ● UTS: Isolation for hostname and NIS domain name. ● USER: Isolates the user and group ID namespaces. Docker Container Introduction
- 18. cGroups (control groups) innfinision.net cGroups (control groups) is a feature of Linux kernel for accounting, limiting and isolation of resources. It provides means to restrict resources that a process can use. Linux container is basically a process or a set of processes that can run in an isolated environment on the host system. Docker Container Introduction
- 19. Copy On Write File System innfinision.netDocker Container Introduction
- 20. Copy On Write Filesystem innfinision.net ● Never overwrites the live data ● It does all the updating using the existing unused blocks in the disk using copy on write functionality ● The new data will be live only when all the data has been updated to the disk Docker Container Introduction
- 21. Copy On Write Filesystem innfinision.netDocker Container Introduction
- 22. innfinision.net ● Resources are handles using Copy on Write (COW) when same data is utilized by multiple tasks. ● Is a read-only, point-in-time copy of the file system state ● Storage snapshot is created using predesignated space allocated to it ● Whenever a snapshot is created, the metadata associated with the original data is stored as a copy ● Snapshot does not create a physical copy and creation of a snapshot is nearly immediate BTRFS Docker Container Introduction
- 23. Advantages of copy-on-write technique innfinision.net ● Space efficiency is main advantage ● More performance but impacted by cow technique Docker Container Introduction
- 24. Docker ? innfinision.netDocker Container Introduction
- 25. Docker innfinision.net From the Docker web site—Docker is “an open source project to pack, ship and run any application as a lightweight container.” Docker platform can be used by developers and system administrators for developing and shipping applications to different environments. Docker Container Introduction
- 26. Docker Leverage innfinision.net ● LXC (Linux Containers) ● Docker is not limited to LXC but can use any other container technology like libcontainer ● Copy-on-Write file system ● “Plain Text” configuration ● Containers sit on top of a union file system Docker Container Introduction
- 27. Introduction Container Image innfinision.netDocker Container Introduction
- 28. Container Image innfinision.net A container is started from an image, which may be locally created, cached locally, or downloaded from a registry. Docker Container Introduction
- 29. Create Aplication Packages for Containers innfinision.net ● Manual builds A manual build starts by launching a container with a base operating system image. Normal process for installation of an application on the operating system is performed. ● Docker File This method is more scripted and automated for construction of a Docker Container. Docker Container Introduction
- 30. Why to use Docker innfinision.netDocker Container Introduction
- 31. Why to use Docker innfinision.net ● Portable Deployments Can be deployed to various environments without making any changes to the container ● Fast application delivery ● Scale and deploy with ease Scaling up and down containers is blazingly fast ● Higher workloads with greater density More container applications can be deployed on a host when compared to virtual machines Docker Container Introduction
- 32. Docker Architecture innfinision.netDocker Container Introduction
- 33. Docker Architecture innfinision.net ● Docker has client server architecture. The Docker client instructs the Docker daemon for all the container specific tasks. ● Docker daemon is carried out through sockets or through REST APIs. ● Docker client and Docker daemon can be on the same host or different hosts. Docker Container Introduction
- 34. Docker Architecture innfinision.netDocker Container Introduction
- 35. Docker internal components innfinision.net ● Docker image – base image An image consists of OS (Ubuntu, CentOS etc.,) and applications installed on it. ● Docker registry Docker registry is a repository for Docker images. It can be public or private. The public Docker registry maintained by Docker is called Docker hub. Docker Container Introduction
- 36. Docker internal components innfinision.net ● Docker Container It is created on top of a Docker image and it is completely isolated. has its own user space, networking and security settings and holds all the necessary files and configurations for running an application. Docker Container Introduction
- 37. How Docker Works innfinision.netDocker Container Introduction
- 38. Working of Docker image innfinision.net Each Docker image is an association of various layers.These layers are combined in to a single unit using Uniform file system (AUFS). AUFS stores every layer as a normal directory, files with AUFS metadata. This ensures that all the files and directories are unique to the particular layer. Docker Container Introduction
- 39. Working of Docker image innfinision.net An image consists of OS (Ubuntu, centos etc.,) and applications installed on it. Docker Container Introduction
- 40. Working of Docker registry innfinision.net Public registry (Docker hub): It contains official Docker images and user created images. ● Private registry: A registry created by a user for storing private Docker images in your datacenter. Docker Container Introduction
- 41. How container works innfinision.net Container is an execution environment for applications. It contains all the operating system files, files added by users and metadata. Container is launched from an image, As the images are in read only format, when a container is launched, a read/write layer will be added on top of the image for the container for the applications to run and make changes to it. Docker Container Introduction
- 42. innfinision.net How container works Docker Container Introduction
- 43. Simple Command To Build Docker Container innfinision.netDocker Container Introduction
- 44. innfinision.net ● Docker checks the specified Docker image If it is present locally, Docker will use that image for creating a container. If not, it will download the image from the registry (based on the Docker host configuration) on the host. ● The local or pulled image will be used for creating a new container. ● Once the image is set, Docker will create a read/write file system over the image. Sudo docker run -i -t ubuntu /bin/bash Docker Container Introduction
- 45. innfinision.net ● Then Docker creates the necessary network interfaces for the container to interact with the host machine. ● Docker checks for available IP address from the pool and allocates one to the container. ● Then it executes the command specified in the command e.g. /bin/bash shell ● Finally it logs all the input/output and errors for the user to find out the status of the container. Sudo docker run -i -t ubuntu /bin/bash Docker Container Introduction