AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
Docker container startup time3/23/2023 Try running the ls command to see the list of files: ls -al total 56 drwxr-xr-x 1 root root 4096 Feb 22 14:22. Once the image is downloaded, Docker runs the image, executing the bash command, which starts an interactive Bash prompt, where you can type. However, it’s also possible to create private Docker images which only certain authenticated users can use. The ubuntu:20.04 image happens to be a public Docker image - an official one maintained by the Docker team - so you’re able to download it without any authentication. If you don’t have that image downloaded already, Docker downloads it automatically from Docker Hub, which is a Docker Registry that contains shared Docker images. How did this happen? Well, first, Docker searches your local file system for the ubuntu:20.04 image. For example, you can look at the contents of /etc/os-release to verify you really are in Ubuntu: cat /etc/os-release NAME="Ubuntu" VERSION="20.04.3 LTS (Focal Fossa)" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 20.04.3 LTS" VERSION_ID="20.04" VERSION_CODENAME=focal For example, here’s how you can run a Bash shell in an Ubuntu 20.04 Docker image (note the command below includes the -it flag so you get an interactive shell where you can type): $ docker run -it ubuntu:20.04 bash Unable to find image ‘ubuntu:20.04’ locally 20.04: Pulling from library/ubuntu Digest: sha256:669e010b58baf5beb2836b253c1fd5768333f0d1dbcb83 (.) Status: Downloaded newer image for ubuntu:20.04 voilà, you’re now in Ubuntu! If you’ve never used Docker before, this can seem fairly magical. Where IMAGE is the Docker image to run and COMMAND is an optional command to execute. You can run Docker images locally using the docker run command, which has the following syntax: $ docker run Once it’s installed, you should have the docker command available on your command line. Let’s get started! Run a Docker containerįirst, if you don’t have Docker installed already, follow the instructions on the Docker website to install Docker Desktop for your operating system. So it’s well worth your time to learn how to use it. VMs (left) virtualize the hardware, whereas containers (right) virtualize only user space.īecause of its portability and minimal overhead, Docker has become one of the most popular ways to package and deploy apps (you’ll see an example of using Kubernetes to deploy Dockerized apps in part 2 of this series). Since all the containers running on a single server share that server’s OS kernel and hardware, containers can boot up in milliseconds and have little CPU or memory overhead. With Docker, you package your software into a Docker image, which is a self-contained snapshot that includes a file system with your code and your code’s dependencies, and you run that image as a container by using a container engine (e.g., Docker engine), which virtualizes the user space (processes, memory, mount points, and networking see user space vs kernel space) of your operating system, isolating your code from the host machine and any other containers, and ensuring your code will run the same way in all environments (your computer, a QA server, a production server, etc.). One drawback with VMs is that virtualizing all the hardware and running a totally separate OS for each VM image incurs a lot of overhead in terms of CPU usage, memory usage, and startup time. With a VM, you package your code into a VM image, which is a self-contained “snapshot” that includes an operating system and a file system with your code and all of your code’s dependencies, and you run that image on top of a hypervisor (e.g., VMWare, VirtualBox) which virtualizes all the hardware (CPU, memory, hard drive, and networking), isolating your code from the host machine and any other VM images, and ensuring your code will run the same way in all environments (e.g., your computer, a QA server, a production server). If you want to go deeper, there are also links at the end of the post to more advanced resources.ĭocker offers a way to package and run your code so that it is portable: that is, so that you can run that code just about anywhere-your own computer, a QA server, a production server-and be confident that it will always run exactly the same way.īefore Docker came along, it was common to use virtual machines (VMs) to package and run code. This course is designed for newbies, starting at zero, and building your mental model step-by-step through simple examples you run on your computer to do something useful with Docker - in minutes. This post will teach you Docker basics by going through a lightning quick crash course where you learn by doing. This is part 1 of the Docker, Kubernetes, Terraform, and AWS crash course series.
0 Comments
Read More
Leave a Reply. |