4.9 KiB
exec
Execute a command in a running container
Aliases
docker container exec, docker exec
Options
| Name | Type | Default | Description |
|---|---|---|---|
-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 | |
--env-file |
list |
Read in a file of 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 |
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" works,
work, but docker exec -it my_container "echo a && echo b" does not.
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