How to access the Docker container’s shell?

This article shows you how to use docker exec -it <container ID or Name> <sh or bash> to access or get into the container’s shell.

# docker exec -it <contaier ID or name> <command>

$ docker exec -it a5df11a07a0e bash
/opt/app #  

$ docker exec -it stoic_bhaskara sh
/opt/app #

The docker exec -it means run a command on a running Docker container, in interactive mode.

1. DockerFile

This docker container is using the openjdk11:alpine-jre image.

FROM adoptopenjdk/openjdk11:alpine-jre

ARG JAR_FILE=target/markdown.jar
ARG SSL_FILE=cert.p12

WORKDIR /opt/app

COPY ${JAR_FILE} webapp.jar
COPY ${SSL_FILE} .

ENTRYPOINT ["java","-jar","webapp.jar"]

2. Access the Docker container’s shell

Build, start and run a webapp in a docker container

$ cd project/webapp/

$ docker build -t webapp:0.1 .

$ docker run -d -p 80:8080 -p 443:8443 -t webapp:0.1  

List all running docker containers.

$ docker ps

CONTAINER ID        IMAGE               COMMAND               CREATED             STATUS              PORTS                                         NAMES
a5df11a07a0e        webapp:0.1    "java -jar app.jar"   8 seconds ago       Up 7 seconds        0.0.0.0:80->8080/tcp, 0.0.0.0:443->8443/tcp   stoic_bhaskara  

This command tries to access the above running docker container’s shell.

# docker exec -it <contaier ID or name> <shell, sh|bash>

$ docker exec -it stoic_bhaskara sh
/opt/app #

$ docker exec -it a5df11a07a0e bash
/opt/app #                 

If we are trying to access something that doesn’t exist:

$ docker exec -it 5c27d3cfdfa3 sh

Error response from daemon: Container 5c27d3cfdfa35c627c323996e5a092ee666cb07bd59285aead8a5ee02a89841c is not running

3. What is -it?

For reference.

$ docker --help

exec        Run a command in a running container

$ docker exec --help

-i, --interactive          Keep STDIN open even if not attached
    --privileged           Give extended privileges to the command
-t, --tty                  Allocate a pseudo-TTY

$ docker exec --help

Usage:  docker exec [OPTIONS] CONTAINER COMMAND [ARG...]

Run a command in a running container

Options:
-d, --detach               Detached mode: run command in the background
    --detach-keys string   Override the key sequence for detaching a
                           container
-e, --env list             Set environment variables
-i, --interactive          Keep STDIN open even if not attached
    --privileged           Give extended privileges to the command
-t, --tty                  Allocate a pseudo-TTY
-u, --user string          Username or UID (format:
                           <name|uid>[:<group|gid>])
-w, --workdir string       Working directory inside the container

References

• docker exec reference