technonotes-hacker

Posted on Oct 16, 2023

Docker A to Z

docker ( double tab )

Help command

docker volume help
docker image help

docker info

docker system information will be displayed.

Above highlighted option will be ENABLED when we use CLUSTER in docker.

docker system df

All images & containers will be displayed.

Docker real-time Events or logs

docker system events

docker system prune

It deletes all image and container.
Its a risky command as it removes unused data & free size.

help or man

man docker system
or
docker system help

docker stats

Usage details are shown here.

docker search busapp

this search command , will get all the application i.e busapp installed in public repository of docker.

docker images

List the images which are present in the system.

Pulling the image from HUB

why am I pulling the image ? To launch a container I need an image.

docker pull httpd
docker images
docker pull alpine

Where these images stored ?

It will be occupying your disc.
Check it with df command.

docker system df

How to run a IMAGE ?

There are two things , one is create & run
CREATE --> Create the container but not in running state.
RUN --> Create the container & run the container too.

docker run --name testing_web httpd
docker ps

--name --> Name for the container 
httpd --> name of the image

But the above one is running in foreground , so you can't perform anything in that window . But the container will come up.

CONTROL + C ( now the container will not be available )

RUN the container in back-ground

docker run -d --name testing_web httpd
docker ps -a ( shows all the container running & stopped )
d --> for demonize which runs in back-ground

Running the same command will end up in error because as we are using the same container name . Even though we stopped but the container is still there. IN other words " Its stopped but still the container is available in that name.

Provide a NEW NAME to the container.

docker run -d --name testing_web_new httpd
docker ps

Lets login to the CONTAINER

docker exec -it testing_web /bin/sh
docker exec -it testing_web /bin/bash

testing_web  --> container name
/bin/sh --> shell type , we ca use bash also.
it --> Interactive terminal

Here the trick is that , NOT all commands we can run inside this container . Check it. Also we are not aware what OS they used to build the image.

It will only files which are related to httpd only.
only these commands can be used inside the container.

Without logging in Can we execute COMMANDS ?

YES
Remove the 'it' from the command.

docker exec testing_web_new uname -a
docker exec testing_web_new hostname
docker exec testing_web_new mkdir /tmp/testing_dir

Copy FILES from local to CONTAINER


docker cp <file_name_local> <container_id/conatiner_name>:<destination>
docker ps
docker cp local_file 6438c81d6841:/tmp
docker exec testing_web_new ls /tmp
docker cp local_file testing_web_new:/tmp

Copy FILES from CONTAINER to Local

docker cp <file_name_local> <container_id/conatiner_name>:<destination>
touch local_to_container
docker ps
docker cp local_to_container 4b:/tmp
docker exec os_service_3 ls /tmp
rm local_to_container
docker cp 4b:/tmp/local_to_container .

Note : 4b --> Nothing but start of the container. You can give in this WAY.

How to START & STOP the CONTAINER?

docker ps -a
docker stop testing_web_new
docker ps -a
docker start testing_web_new
docker start testing_web

System related check for these containers

docker system df
docker stats
docker stats <container_name>
docker top <container_name>

How to remove the CONTAINER ?

Keep in Mind " You cant remove a RUNNING Container ". But we can with FORCE option.

Before remove , STOP the container. ( safest way )

docker ps
docker rm testing_web_new
docker rm -f testing_web_new
docker ps
docker stop testing_web
docker rm testing_web
docker ps

docker logs

By giving the container Name , we can check the logs.
Start logs only visible.

LETS start the alpine and check the logs.

Above screen shows Alpine is started but its not running.
Alpine is just a OS , so we need to provide what type of bash is required.

docker run -d --name os_service_2 alpine /bin/sh --> NOT WORKING / ERROR
docker run -d --name os_service_1 alpine /bin/sh --> NOT WORKING / ERROR
docker run -d -it --name os_service_3 alpine /bin/sh