Tinkle7/docker_data

create and run

docker run <image name>

• docker Reference the Docker client
• if the image is not there it will get the image from the hub
• create a container from the image
• start the container

  Warning Run for a short time then it will close.

default command override

/* Run the container with the alternative command. */

docker run <image name> command

Example

/* ls gives you all the files in the container. */

docker run busybox ls

/* echo hi gives hi in the terminal. */

docker run busybox echo hi

/* ping google.com help to run the program infinitely. */

docker run busybox ping google.com

+  run for long time `Cntrl + C` to stop

Warning ls and echo are two programs inside the busybox file system if it's not it throws you an error.

docker ps

/* List all running containers. */

docker ps

/* List all running containers that ever run in my machine. */

docker ps --all  |  docker ps -a

Note docker ps help to get the id of all containers.

container lifecycle

+ docker run = ducker create + ducker start

/* Create a container. */

docker create <image name>

/* Start a container. */

docker start <container id>

Note >docker start not gonna show you information coming out from the terminal, but docker run show you information coming out from the terminal.

/* Start a container with logs. */

docker start -a <container id>

_{"-a" watch for output from the container and give it to your terminal.}

Restarting Stopped Containers

• docker ps --all from this we can get the container id.
• docker start -a <container id> restart the stopped container.

  Warning We can not displace the default command.

Removing Stopped Containers

/* delete stopped containers + networks not used by at least one container + all dangling images + all build cache */

docker system prune

Retrieving Log Outputs

Note > docker start is sometimes an expensive process it takes time. "-a" can't help you all time.

/* Getting a record of all the logs that have been emitted from the container(inspect the container) */

docker logs <container id>

Stopping Containers

ideal method ✔️

/* sent SIGTERM command to the container. */

docker stop <container id>

It gives some time to the container to save some files or do some cleaning before shutdown.

/* sent SIGKILL command to the container. */

docker kill <container id>

It shut down immediately

Warning If the ping command SIGTERM is not going to shut down the container in 10sec then docker falls back and ping command SIGKILL.

Multi-Command Containers

Executing commands in Running Containers

docker exec -it <container id> <command>

• exec Run another command.
• -it Allows us to Provide input to the container.
• <container id> ID of the container
• <command> Command to execute

Example

first terminal.

/* run Redis in one container */

docker run redis

second terminal.

/* get the id of running Redis container */

docker ps

/* run another command in the same container */

docker exec -it f00035b5c219 redis-cli

/* try some command */

set myvalue 5

get myvalue // "5"

The Purpose of the IT Flag

flowchart TD
A[redis-cli]
B[STDIN]
C[STDOUT]
D[STDERR]
E[Terminal]
F[fa:fa-computer screen]
    B -->|proceed command| A
    A -->|proceed O/P| C
    A -->|proceed O/P| D
    E -->|send command| B
    C -->|send O/P| F
    D -->|send O/P| F

Note Running processes are (ex:- echo hi there / redis-cli) created in a Linux environment It attaches to three communication channels.

@@ -it = -i + -t @@

• -i we execute this new command inside the container we want to attach our terminal to the standard in the channel of that new running process.
• -t all text from your terminal going out and coming in the show in a nice format on your screen.

Getting a Command prompt in a container

/* getting a Command prompt in a container */

docker exec -it <container id> sh

It is the name of a program. it's a program that is being executed inside the container. It is a command processor or a shell. It is something that allows us to type commands in and have them be executed inside that container

examples: -> `sh / bash / PowerShell

Note >ctrl + Dgetting out from Command prompt in a container || type exit

Starting with a Shell

/* run a single program with a shell */

docker run -it <image name> sh

Container Location

/* create a new file in a container */

touch <file name>

+ Containers are separate and isolated from each other if we don't make a connection between them.
+ Also, containers can be from the same images but they contain different file systems.