mirror of https://github.com/docker/cli.git
142 lines
4.3 KiB
Markdown
142 lines
4.3 KiB
Markdown
---
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title: "exec"
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description: "The exec command description and usage"
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keywords: "command, container, run, execute"
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---
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# exec
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```markdown
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Usage: docker exec [OPTIONS] CONTAINER COMMAND [ARG...]
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Execute a command in a running container
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Aliases:
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docker container exec, docker exec
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Options:
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-d, --detach Detached mode: run command in the background
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--detach-keys Override the key sequence for detaching a container
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-e, --env=[] Set environment variables
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--env-file Read in a file of environment variables
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--help Print usage
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-i, --interactive Keep STDIN open even if not attached
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--privileged Give extended privileges to the command
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-t, --tty Allocate a pseudo-TTY
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-u, --user Username or UID (format: <name|uid>[:<group|gid>])
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-w, --workdir Working directory inside the container
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```
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## Description
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The `docker exec` command runs a new command in a running container.
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The command started using `docker exec` only runs while the container's primary
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process (`PID 1`) is running, and it is not restarted if the container is
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restarted.
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COMMAND runs in the default directory of the container. If the underlying image
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has a custom directory specified with the WORKDIR directive in its Dockerfile,
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this directory is used instead.
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COMMAND must be an executable. A chained or a quoted command does not work.
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For example, `docker exec -it my_container sh -c "echo a && echo b"` works,
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work, but `docker exec -it my_container "echo a && echo b"` does not.
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## Examples
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### Run `docker exec` on a running container
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First, start a container.
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```console
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$ docker run --name mycontainer -d -i -t alpine /bin/sh
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```
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This creates and starts a container named `mycontainer` from an `alpine` image
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with an `sh` shell as its main process. The `-d` option (shorthand for `--detach`)
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sets the container to run in the background, in detached mode, with a pseudo-TTY
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attached (`-t`). The `-i` option is set to keep `STDIN` attached (`-i`), which
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prevents the `sh` process from exiting immediately.
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Next, execute a command on the container.
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```console
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$ docker exec -d mycontainer touch /tmp/execWorks
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```
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This creates a new file `/tmp/execWorks` inside the running container
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`mycontainer`, in the background.
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Next, execute an interactive `sh` shell on the container.
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```console
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$ docker exec -it mycontainer sh
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```
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This starts a new shell session in the container `mycontainer`.
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### <a name=env></a> Set environment variables for the exec process (--env, -e)
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Next, set environment variables in the current bash session.
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By default, the `docker exec` command, inherits the environment variables that
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are set at the time the container is created. Use the `--env` (or the `-e` shorthand)
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to override global environment variables, or to set additional environment variables
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for the process started by `docker exec`.
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The example below creates a new shell session in the container `mycontainer` with
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environment variables `$VAR_A` and `$VAR_B` set to "1" and "2" respectively.
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These environment variables are only valid for the `sh` process started by that
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`docker exec` command, and are not available to other processes running inside
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the container.
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```console
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$ docker exec -e VAR_A=1 -e VAR_B=2 mycontainer env
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PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
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HOSTNAME=f64a4851eb71
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VAR_A=1
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VAR_B=2
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HOME=/root
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```
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### <a name=workdir></a> Set the working directory for the exec process (--workdir, -w)
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By default `docker exec` command runs in the same working directory set when
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the container was created.
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```console
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$ docker exec -it mycontainer pwd
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/
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```
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You can specify an alternative working directory for the command to execute
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using the `--workdir` option (or the `-w` shorthand):
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```console
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$ docker exec -it -w /root mycontainer pwd
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/root
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```
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### Try to run `docker exec` on a paused container
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If the container is paused, then the `docker exec` command fails with an error:
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```console
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$ docker pause mycontainer
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mycontainer
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$ docker ps
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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482efdf39fac alpine "/bin/sh" 17 seconds ago Up 16 seconds (Paused) mycontainer
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$ docker exec mycontainer sh
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Error response from daemon: Container mycontainer is paused, unpause the container before exec
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$ echo $?
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1
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```
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