I am getting into Docker and am trying to better understand how it works out there in the "real world".
It occurs to me that, in practice:
You need a way to version Docker images
You need a way to tell the Docker engine (running on a VM) to stop/start/restart a particular container
You need a way to tell the Docker engine which version of a image to run
Does Docker ship with built-in commands for handling each of these? If not what tools/strategies are used for accomplishing them? Also, when I build a Docker image (via, say, docker build -t myapp .), what file type is produced and where is it located on the machine?
docker has all you need to build images and run containers. You can create your own image by writing a Dockerfile or by pulling it from the docker hub.
In the Dockerfile you specify another image as the basis for your image, run command install things. Images can have tags, for example the ubuntu image can have the latest or 12.04 tag, that can be specified with ubuntu:latest notation.
Once you have built the image with docker build -t image-name . you can create containers from that image with `docker run --name container-name image-name.
docker ps to see running containers
docker rm <container name/id> to remove containers
Suppose we have a docker file like bellow:
->Build from git without versioning:
sudo docker build https://github.com/lordash/mswpw.git#fecomments:comments
in here:
fecomments is branch name and comments is the folder name.
->building from git with tag and version:
sudo docker build https://github.com/lordash/mswpw.git#fecomments:comments -t lordash/comments:v1.0
->Now if you want to build from a directory: first go to comments directory the run command sudo docker build .
->if you want to add tag you can use -t or -tag flag to do that:
sudo docker build -t lordash . or sudo docker build -t lordash/comments .
-> Now you can version your image with the help of tag:
sudo docker build -t lordash/comments:v1.0 .
->you can also apply multiple tag to an image:
sudo docker build -t lordash/comments:latest -t lordash/comments:v1.0 .
Related
I need to have an ubuntu image and then run a build process using that image. All is well until the build gets to the point of doing docker build etc.
Lets say I use the following to test this:
Dockerfile
FROM ubuntu:latest
I then build that - docker build -t ubuntudkr .
Next, I run it like:
docker run -ti -v /var/run/docker.sock:/var/run/docker.sock ubuntudkr
When I then run docker ps inside this container, I get the error bash: docker: command not found
All the examples I've found says I need to run:
docker run -v /var/run/docker.sock:/var/run/docker.sock \
-ti docker
They all use the docker image which contains the docker library. Is my answer then to install docker inside my base image to make it work? Does this then not go against what docker themselves says?
There are many other blog posts out there that gave the same advice, but my example does work. Where do I go wrong?
Replace the image ubuntu:latest in your dockerfile by the official docker:latest image wich contains docker binaries and does exactly what you want: https://hub.docker.com/_/docker
If you want to keep the Ubuntu image, you must install Docker tools following your error. By default, the Ubuntu image does not contain Docker binaries as a regular Ubuntu installation.
I am using ubuntu 18.04
I have docker-ce installed
I have a file named Dockerfile
I didn't have any other files
how can I start using this container
Firstly you need to build an image from Dockerfile. To do this:
Go to the directory containing Dockerfile
Run (change <image_name> to some meaningful name): docker build -t <image_name> .
After image is built we can finally run it: docker run -it <image_name>
There multiple options how the image can be run so I encourage you to read some docs.
I am learning Docker
docker build -t mm/cowsay .
Should I go to cowsay folder or should I run it from my home mm directory?
I have registered on Docker hub.
The docker build command follows instructions specified in a given Dockerfile, and outputs an image.
Syntax:
docker build \
-t <tag-of-output-image> \
-f <path-to-dockerfile>
If you use . instead of -f <path-to-dockerfile>, you are telling the Docker Engine to use the Dockerfile in the current directory.
So you need to run your command from where the Dockerfile exists.
I'm learning how to use docker.
I want to deploy a microservice for swagger. I can do
docker pull schickling/swagger-ui
docker run -p 80:8080 -e API_URL=http://myapiurl/api.json swaggerapi/swagger-ui
To deploy it, I need a dockerfile i can run.
How do i generate the dockerfile in a way I can run it with docker build ?
The original question asks for a Dockerfile, perhaps for some CI/CD workflow, so this answer addresses that requirement:
Create a very simple Dockerfile beginning with
FROM schickling/swagger-ui
Then from that directory run
$ docker build -t mycontainername .
Which can then be run:
$ docker run -p 80:8080 -e API_URL=http://myapiurl/api.json mycontainername
Usually the docker pull pulls the Dockerfile. The Dockerfile for swagger is on the docker repo for it if you wanted to edit it or customize it.
(https://hub.docker.com/r/schickling/swagger-ui/~/dockerfile/)
That one should work with the build command. The build command builds the image, the run command turns the image into a container. The docker pull command should pull the image in. You don't need to run docker build for it as you should already have the image from the pull. You only need to do docker run.
I have successfully shelled into a RUNNING docker container using
docker exec -i -t 7be21f1544a5 bash
I have made some changes to some json files and wanted to apply these changes to reflect online.
I am a beginner and have tried to restart, mount in vain. What strings I have to replace when I mount using docker run?
Is there any online sample?
CONTAINER ID: 7be21f1544a5
IMAGE: gater/web
COMMAND: "/bin/sh -c 'nginx'"
CREATED: 4 weeks ago
STATUS: Up 44 minutes
PORTS: 443/tcp, 172.16.0.1:10010->80/tcp
NAMES: web
You can run either create a Dockefile and run:
docker build .
from the same directory where your Dockerfile is located.
or you can run:
docker run -i -t <docker-image> bash
or (if your container is already running)
docker exec -i -t <container-id> bash
once you are in the shell make all the changes you please. Then run:
docker commit <container-id> myimage:0.1
You will have a new docker image locally myimage:0.1. If you want to push to a docker repository (dockerhub or your private docker repo) you can run:
docker push myimage:0.1
There are 2 ways to do it :
Dockerfile approach
You need to know what changes you have made into Docker container after you have exec into it and also the Dockerfile of the image .
Lets say you installed additional rpm using yum install command after entering into the container (yum install perl-HTML-Format) and updated some file say /opt/test.json inside contianer (take a backup of this file in Docker host in some directory or in directory Dockerfile exist)
The above command/steps you can place in Dockerfile as
RUN yum install perl-HTML-Format
COPY /docker-host-dir/updated-test.json /opt/test.json
Once you update the Dockerfile, create the new image and push it to Docker repository
docker build -t test_image .
docker push test_image:latest
You can save the updated Dockerfile for future use.
Docker commit command approach
After you made the changes to container, use below commands to create a new image from container's changes and push it online
docker commit container-id test_image
docker push test_image
docker commit --help
Usage: docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]
You don't want to do that. After you figured out what you needed you throw away the running container (git rm 7be21f1544a5), repeat the changes in the Dockerfile and build a new image to run.