Thread by @FrancescoCiull4

docker exec

One of the most important CLI commands to debug/modify running containers on the Docker Host.

It runs a specific command in an already running container

Syntax:
docker exec [OPTIONS] <container_id> COMMAND [ARUMENTS...]

Example:
`docker exec 1234 echo "hi"`

...

Common options:

-d: Run in detached mode
-e: Set new environment variable
--env-file: use an external file for env variables
-i: Keep the Standard Input open
-t: pseudo Terminal (TTY)
-u: define a user for the command
-w: define a working dir inside the container

...

The most common use case:

Use the exec command to get inside a running container

Example:
`docker exec -it <container_id> bash`

This works for most of the containers running based on Linux images

...

If you use Alpine distributions, you could not have a bash.

in this case, you can use sh:
`docker exec -it <container_id> sh`

As an alternative, you can install the bash in the Dockerfile.

...

Another use Case

If you use Postgres and you wanna see the database directly from the Postgres container is:

`docker exec -it <container_id> psql -U Postgres