docker exec


Execute a command in a running container

Usage

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

Refer to the options section for an overview of available OPTIONS for this command.

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 runs in the default directory of the container. If the underlying image has a custom directory specified with the WORKDIR directive in its Dockerfile, this directory is used instead.

COMMAND must be an executable. A chained or a quoted command does not work. For example, docker exec -it my_container sh -c "echo a && echo b" does work, but docker exec -it my_container "echo a && echo b" does not.

For example uses of this command, refer to the examples section below.

Options

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

Examples

Run docker exec on a running container

First, start a container.

$ docker run --name mycontainer -d -i -t alpine /bin/sh

This creates and starts a container named mycontainer from an alpine image with an sh shell as its main process. The -d option (shorthand for --detach) sets the container to run in the background, in detached mode, with a pseudo-TTY attached (-t). The -i option is set to keep STDIN attached (-i), which prevents the sh process from exiting immediately.

Next, execute a command on the container.

$ docker exec -d mycontainer touch /tmp/execWorks

This creates a new file /tmp/execWorks inside the running container mycontainer, in the background.

Next, execute an interactive sh shell on the container.

$ docker exec -it mycontainer sh

This starts a new shell session in the container mycontainer.

Set environment variables for the exec process (--env, -e)

Next, set environment variables in the current bash session.

By default, the docker exec command, inherits the environment variables that are set at the time the container is created. Use the --env (or the -e shorthand) to override global environment variables, or to set additional environment variables for the process started by docker exec.

The example below creates a new shell session in the container mycontainer with environment variables $VAR_A and $VAR_B set to “1” and “2” respectively. These environment variables are only valid for the sh process started by that docker exec command, and are not available to other processes running inside the container.

$ docker exec -e VAR_A=1 -e VAR_B=2 mycontainer env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=f64a4851eb71
VAR_A=1
VAR_B=2
HOME=/root

Set the working directory for the exec process (--workdir, -w)

By default docker exec command runs in the same working directory set when the container was created.

$ docker exec -it mycontainer pwd
/

You can specify an alternative working directory for the command to execute using the --workdir option (or the -w shorthand):

$ docker exec -it -w /root mycontainer pwd
/root

Try to run docker exec on a paused container

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

$ docker pause mycontainer
mycontainer

$ docker ps

CONTAINER ID   IMAGE     COMMAND     CREATED          STATUS                   PORTS     NAMES
482efdf39fac   alpine    "/bin/sh"   17 seconds ago   Up 16 seconds (Paused)             mycontainer

$ docker exec mycontainer sh

Error response from daemon: Container mycontainer is paused, unpause the container before exec

$ echo $?
1