docker exec

Estimated reading time: 3 minutes

Description

Run a command in a running container

Usage

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

Options

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

Parent command

Command Description
docker The base command for the Docker CLI.

Extended description

The docker exec command runs a new command in a running container.

The command started using docker exec only runs while the container’s primary process (PID 1) is running, and it is not restarted if the container is restarted.

COMMAND will run in the default directory of the container. It the underlying image has a custom directory specified with the WORKDIR directive in its Dockerfile, this will be used instead.

COMMAND should be an executable, a chained or a quoted command will not work. Example: docker exec -ti my_container "echo a && echo b" will not work, but docker exec -ti my_container sh -c "echo a && echo b" will.

Examples

Run docker exec on a running container

First, start a container.

$ docker run --name ubuntu_bash --rm -i -t ubuntu bash

This will create a container named ubuntu_bash and start a Bash session.

Next, execute a command on the container.

$ docker exec -d ubuntu_bash touch /tmp/execWorks

This will create a new file /tmp/execWorks inside the running container ubuntu_bash, in the background.

Next, execute an interactive bash shell on the container.

$ docker exec -it ubuntu_bash bash

This will create a new Bash session in the container ubuntu_bash.

Next, set an environment variable in the current bash session.

$ docker exec -it -e VAR=1 ubuntu_bash bash

This will create a new Bash session in the container ubuntu_bash with environment variable $VAR set to “1”. Note that this environment variable will only be valid on the current Bash session.

Try to run docker exec on a paused container

If the container is paused, then the docker exec command will fail with an error:

$ docker pause test

test

$ docker ps

CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                   PORTS               NAMES
1ae3b36715d2        ubuntu:latest       "bash"              17 seconds ago      Up 16 seconds (Paused)                       test

$ docker exec test ls

FATA[0000] Error response from daemon: Container test is paused, unpause the container before exec

$ echo $?
1