mirror of https://github.com/docker/cli.git
139 lines
4.9 KiB
Markdown
139 lines
4.9 KiB
Markdown
# exec
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<!---MARKER_GEN_START-->
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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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| Name | Type | Default | Description |
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|:------------------------------------------|:---------|:--------|:-------------------------------------------------------|
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| `-d`, `--detach` | | | Detached mode: run command in the background |
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| `--detach-keys` | `string` | | Override the key sequence for detaching a container |
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| [`-e`](#env), [`--env`](#env) | `list` | | Set environment variables |
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| `--env-file` | `list` | | Read in a file of environment variables |
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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` | `string` | | Username or UID (format: `<name\|uid>[:<group\|gid>]`) |
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| [`-w`](#workdir), [`--workdir`](#workdir) | `string` | | Working directory inside the container |
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<!---MARKER_GEN_END-->
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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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