docs/reference/commandline/attach.md - external/github.com/docker/cli - Git at Google

 ---
 title: "attach"
 description: "The attach command description and usage"
 keywords: "attach, running, container"
 ---

 <!-- This file is maintained within the docker/cli GitHub
      repository at https://github.com/docker/cli/. Make all
      pull requests against that repo. If you see this file in
      another repository, consider it read-only there, as it will
      periodically be overwritten by the definitive file. Pull
      requests which include edits to this file in other repositories
      will be rejected.
 -->

 # attach

 ```markdown
 Usage: docker attach [OPTIONS] CONTAINER

 Attach local standard input, output, and error streams to a running container

 Options:
       --detach-keys string   Override the key sequence for detaching a container
       --help                 Print usage
       --no-stdin             Do not attach STDIN
       --sig-proxy            Proxy all received signals to the process (default true)
 ```

 ## Description

 Use `docker attach` to attach your terminal's standard input, output, and error
 (or any combination of the three) to a running container using the container's
 ID or name. This allows you to view its ongoing output or to control it
 interactively, as though the commands were running directly in your terminal.

 > **Note:**
 > The `attach` command will display the output of the `ENTRYPOINT/CMD` process.  This
 > can appear as if the attach command is hung when in fact the process may simply
 > not be interacting with the terminal at that time.

 You can attach to the same contained process multiple times simultaneously,
 from different sessions on the Docker host.

 To stop a container, use `CTRL-c`. This key sequence sends `SIGKILL` to the
 container. If `--sig-proxy` is true (the default),`CTRL-c` sends a `SIGINT` to
 the container. You can detach from a container and leave it running using the
  `CTRL-p CTRL-q` key sequence.

 > **Note:**
 > A process running as PID 1 inside a container is treated specially by
 > Linux: it ignores any signal with the default action. So, the process
 > will not terminate on `SIGINT` or `SIGTERM` unless it is coded to do
 > so.

 It is forbidden to redirect the standard input of a `docker attach` command
 while attaching to a tty-enabled container (i.e.: launched with `-t`).

 While a client is connected to container's stdio using `docker attach`, Docker
 uses a ~1MB memory buffer to maximize the throughput of the application. If
 this buffer is filled, the speed of the API connection will start to have an
 effect on the process output writing speed. This is similar to other
 applications like SSH. Because of this, it is not recommended to run
 performance critical applications that generate a lot of output in the
 foreground over a slow client connection. Instead, users should use the
 `docker logs` command to get access to the logs.

 ### Override the detach sequence

 If you want, you can configure an override the Docker key sequence for detach.
 This is useful if the Docker default sequence conflicts with key sequence you
 use for other applications. There are two ways to define your own detach key
 sequence, as a per-container override or as a configuration property on  your
 entire configuration.

 To override the sequence for an individual container, use the
 `--detach-keys="<sequence>"` flag with the `docker attach` command. The format of
 the `<sequence>` is either a letter [a-Z], or the `ctrl-` combined with any of
 the following:

 * `a-z` (a single lowercase alpha character )
 * `@` (at sign)
 * `[` (left bracket)
 * `\\` (two backward slashes)
 *  `_` (underscore)
 * `^` (caret)

 These `a`, `ctrl-a`, `X`, or `ctrl-\\` values are all examples of valid key
 sequences. To configure a different configuration default key sequence for all
 containers, see [**Configuration file** section](cli.md#configuration-files).

 ## Examples

 ### Attach to and detach from a running container

 ```bash
 $ docker run -d --name topdemo ubuntu /usr/bin/top -b

 $ docker attach topdemo

 top - 02:05:52 up  3:05,  0 users,  load average: 0.01, 0.02, 0.05
 Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie
 Cpu(s):  0.1%us,  0.2%sy,  0.0%ni, 99.7%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
 Mem:    373572k total,   355560k used,    18012k free,    27872k buffers
 Swap:   786428k total,        0k used,   786428k free,   221740k cached

 PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
  1 root      20   0 17200 1116  912 R    0  0.3   0:00.03 top

  top - 02:05:55 up  3:05,  0 users,  load average: 0.01, 0.02, 0.05
  Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie
  Cpu(s):  0.0%us,  0.2%sy,  0.0%ni, 99.8%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
  Mem:    373572k total,   355244k used,    18328k free,    27872k buffers
  Swap:   786428k total,        0k used,   786428k free,   221776k cached

    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
        1 root      20   0 17208 1144  932 R    0  0.3   0:00.03 top


  top - 02:05:58 up  3:06,  0 users,  load average: 0.01, 0.02, 0.05
  Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie
  Cpu(s):  0.2%us,  0.3%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
  Mem:    373572k total,   355780k used,    17792k free,    27880k buffers
  Swap:   786428k total,        0k used,   786428k free,   221776k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
       1 root      20   0 17208 1144  932 R    0  0.3   0:00.03 top
 ^C$

 $ echo $?
 0
 $ docker ps -a | grep topdemo

 7998ac8581f9        ubuntu:14.04        "/usr/bin/top -b"   38 seconds ago      Exited (0) 21 seconds ago                          topdemo
 ```

 ### Get the exit code of the container's command

 And in this second example, you can see the exit code returned by the `bash`
 process is returned by the `docker attach` command to its caller too:

 ```bash
     $ docker run --name test -d -it debian

     275c44472aebd77c926d4527885bb09f2f6db21d878c75f0a1c212c03d3bcfab

     $ docker attach test

     root@f38c87f2a42d:/# exit 13

     exit

     $ echo $?

     13

     $ docker ps -a | grep test

     275c44472aeb        debian:7            "/bin/bash"         26 seconds ago      Exited (13) 17 seconds ago                         test
 ```
	---
	title: "attach"
	description: "The attach command description and usage"
	keywords: "attach, running, container"
	---

	<!-- This file is maintained within the docker/cli GitHub
	repository at https://github.com/docker/cli/. Make all
	pull requests against that repo. If you see this file in
	another repository, consider it read-only there, as it will
	periodically be overwritten by the definitive file. Pull
	requests which include edits to this file in other repositories
	will be rejected.
	-->

	# attach

	```markdown
	Usage: docker attach [OPTIONS] CONTAINER

	Attach local standard input, output, and error streams to a running container

	Options:
	--detach-keys string Override the key sequence for detaching a container
	--help Print usage
	--no-stdin Do not attach STDIN
	--sig-proxy Proxy all received signals to the process (default true)
	```

	## Description

	Use `docker attach` to attach your terminal's standard input, output, and error
	(or any combination of the three) to a running container using the container's
	ID or name. This allows you to view its ongoing output or to control it
	interactively, as though the commands were running directly in your terminal.

	> Note:
	> The `attach` command will display the output of the `ENTRYPOINT/CMD` process. This
	> can appear as if the attach command is hung when in fact the process may simply
	> not be interacting with the terminal at that time.

	You can attach to the same contained process multiple times simultaneously,
	from different sessions on the Docker host.

	To stop a container, use `CTRL-c`. This key sequence sends `SIGKILL` to the
	container. If `--sig-proxy` is true (the default),`CTRL-c` sends a `SIGINT` to
	the container. You can detach from a container and leave it running using the
	`CTRL-p CTRL-q` key sequence.

	> Note:
	> A process running as PID 1 inside a container is treated specially by
	> Linux: it ignores any signal with the default action. So, the process
	> will not terminate on `SIGINT` or `SIGTERM` unless it is coded to do
	> so.

	It is forbidden to redirect the standard input of a `docker attach` command
	while attaching to a tty-enabled container (i.e.: launched with `-t`).

	While a client is connected to container's stdio using `docker attach`, Docker
	uses a ~1MB memory buffer to maximize the throughput of the application. If
	this buffer is filled, the speed of the API connection will start to have an
	effect on the process output writing speed. This is similar to other
	applications like SSH. Because of this, it is not recommended to run
	performance critical applications that generate a lot of output in the
	foreground over a slow client connection. Instead, users should use the
	`docker logs` command to get access to the logs.

	### Override the detach sequence

	If you want, you can configure an override the Docker key sequence for detach.
	This is useful if the Docker default sequence conflicts with key sequence you
	use for other applications. There are two ways to define your own detach key
	sequence, as a per-container override or as a configuration property on your
	entire configuration.

	To override the sequence for an individual container, use the
	`--detach-keys="<sequence>"` flag with the `docker attach` command. The format of
	the `<sequence>` is either a letter [a-Z], or the `ctrl-` combined with any of
	the following:

	* `a-z` (a single lowercase alpha character )
	* `@` (at sign)
	* `[` (left bracket)
	* `\\` (two backward slashes)
	* `_` (underscore)
	* `^` (caret)

	These `a`, `ctrl-a`, `X`, or `ctrl-\\` values are all examples of valid key
	sequences. To configure a different configuration default key sequence for all
	containers, see [Configuration file section](cli.md#configuration-files).

	## Examples

	### Attach to and detach from a running container

	```bash
	$ docker run -d --name topdemo ubuntu /usr/bin/top -b

	$ docker attach topdemo

	top - 02:05:52 up 3:05, 0 users, load average: 0.01, 0.02, 0.05
	Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
	Cpu(s): 0.1%us, 0.2%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
	Mem: 373572k total, 355560k used, 18012k free, 27872k buffers
	Swap: 786428k total, 0k used, 786428k free, 221740k cached

	PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
	1 root 20 0 17200 1116 912 R 0 0.3 0:00.03 top

	top - 02:05:55 up 3:05, 0 users, load average: 0.01, 0.02, 0.05
	Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
	Cpu(s): 0.0%us, 0.2%sy, 0.0%ni, 99.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
	Mem: 373572k total, 355244k used, 18328k free, 27872k buffers
	Swap: 786428k total, 0k used, 786428k free, 221776k cached

	PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
	1 root 20 0 17208 1144 932 R 0 0.3 0:00.03 top


	top - 02:05:58 up 3:06, 0 users, load average: 0.01, 0.02, 0.05
	Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
	Cpu(s): 0.2%us, 0.3%sy, 0.0%ni, 99.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
	Mem: 373572k total, 355780k used, 17792k free, 27880k buffers
	Swap: 786428k total, 0k used, 786428k free, 221776k cached

	PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
	1 root 20 0 17208 1144 932 R 0 0.3 0:00.03 top
	^C$

	$ echo $?
	0
	$ docker ps -a \| grep topdemo

	7998ac8581f9 ubuntu:14.04 "/usr/bin/top -b" 38 seconds ago Exited (0) 21 seconds ago topdemo
	```

	### Get the exit code of the container's command

	And in this second example, you can see the exit code returned by the `bash`
	process is returned by the `docker attach` command to its caller too:

	```bash
	$ docker run --name test -d -it debian

	275c44472aebd77c926d4527885bb09f2f6db21d878c75f0a1c212c03d3bcfab

	$ docker attach test

	root@f38c87f2a42d:/# exit 13

	exit

	$ echo $?

	13

	$ docker ps -a \| grep test

	275c44472aeb debian:7 "/bin/bash" 26 seconds ago Exited (13) 17 seconds ago test
	```