As a web-dev in the microservices era you will encounter Docker sooner than later. It's always good to have the essential commands at arm's reach. Following is a list of Essential Docker commands that have helped me on a daily basis, hope this helps yo too. Happy Hacking!
Docker Commands
Docker run command
docker run <image-name>
example
docker run hello-world
To add a override command
docker run <image-name> <default command override>
example
docker run busybox ls
List all the running containers
Docker ps command specifically shows running containers
docker ps
Show all container ever run on machine
docker ps --all
Docker ps is also used to get the ID of coantainer
docker run = docker create + docker start
- when we create container we just prep it with say file sysytem etc
- When we run the container then we provide the default command that runs the program
docker create hello-world
now we use the id to start
docker start -a 3c8a5bb0fe7153955d1261054e5b4c99f757920f7760fa7c07803cdbee4b36c1
-a argument watches for any output and prints it on terminal
To re-run an exitied container
first we get the conatiner of ID with ps command
docker ps --all
Then use the id with start command
docker start -a 1285b5630516
When we re-run / restart a container we cannot replace the default command, it automatically takes the default command on re-run with commond it was created with.
Removing stopped containers
docker system prune
Docker logs command
Docker logs command shows all the output of con tainer when it had been running
docker logs 73e564097bd5e6689c2bc5687c038dca99ec77d8716f7ff9eeab9434d422bb8d
Stopping a running container
docker stop <container-id>
This sends a SIGTERM signal allowing container to shut down in some time usually 10s, after that it issues Docker kill anyway
docker kill <container-id>
This command issues a SIGKILL that immediately stops the container
Docker stop is better way to stop*
Executing commands in running containers
docker exec -it <container-id> <command>
- exec command allows us to type extra commands
- it flag helps us to enter text and send it to container
The it flag
- its a -i and -t
- i attaches our terminal to STDIN
- t flag makes sure that it shows the output formatted on terminal, like auto complete you see with redis-cli
How to get shell access in docker container
sh is command processor like bash, zsh etc
docker exec -it <container-id> sh
if ctrl + c doesnt help you exit use ctrl+d or just type exit
starting container with a shell
docker run -it <container-name> sh
Creating a Docker image
Flow to Creating a DockerFile
- specify base image
- Run some commands to install additional programs
- specify command to run on container startup
Sample docker file to create redis image
Create a file named Dockerfile no extension just Dockerfile
# Use an existing docker image as base
FROM alpine
# Download and install a dependency
RUN apk add --update redis
# Tell the image what to do when it starts as a container
CMD ["redis-server"]
use the docker build command to build image
docker build .
Run the image as usual
Writing a docker file == say, given a computer with no OS and being asked to install chrome
Tagging an image
docker build -t <docker-hub -id>/<project>:<version> . Dont forget the dot at the end.
to run the image
docker run <docker-hub -id>/<project>
this automatically takes the latest version.
Technically, the version number at the end is the actual tag here
Manual image generation with docker commit
docker commit -c 'CMD ["<command>"]' <container id>
Copy build files
COPY <relative local file system> <relative dest>
Port forwarding
docker run -p <portno> : <container-port-no> <image-id>
Specifying a working directory
WORKDIR /usr/app
Any following commands will be executed relative to working dir
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