mirror of https://github.com/docker/cli.git
168 lines
6.4 KiB
Markdown
168 lines
6.4 KiB
Markdown
# attach
|
|
|
|
<!---MARKER_GEN_START-->
|
|
Attach local standard input, output, and error streams to a running container
|
|
|
|
### Aliases
|
|
|
|
`docker container attach`, `docker attach`
|
|
|
|
### Options
|
|
|
|
| Name | Type | Default | Description |
|
|
|:--------------------------------|:---------|:--------|:----------------------------------------------------|
|
|
| [`--detach-keys`](#detach-keys) | `string` | | Override the key sequence for detaching a container |
|
|
| `--no-stdin` | | | Do not attach STDIN |
|
|
| `--sig-proxy` | `bool` | `true` | Proxy all received signals to the process |
|
|
|
|
|
|
<!---MARKER_GEN_END-->
|
|
|
|
## 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 lets you view its output or control it interactively, as
|
|
though the commands were running directly in your terminal.
|
|
|
|
> **Note**
|
|
>
|
|
> The `attach` command displays the output of the container's `ENTRYPOINT` and
|
|
> `CMD` process. This can appear as if the attach command is hung when in fact
|
|
> the process may simply not be writing any output 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. If the container was run with `-i` and `-t`, 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
|
|
> doesn't terminate on `SIGINT` or `SIGTERM` unless it's coded to do so.
|
|
|
|
You can't redirect the standard input of a `docker attach` command while
|
|
attaching to a TTY-enabled container (using the `-i` and `-t` options).
|
|
|
|
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.
|
|
Once this buffer is full, the speed of the API connection is affected, and so
|
|
this impacts the output process' writing speed. This is similar to other
|
|
applications like SSH. Because of this, it isn't recommended to run
|
|
performance-critical applications that generate a lot of output in the
|
|
foreground over a slow client connection. Instead, use the `docker logs`
|
|
command to get access to the logs.
|
|
|
|
## Examples
|
|
|
|
### Attach to and detach from a running container
|
|
|
|
The following example starts an Alpine container running `top` in detached mode,
|
|
then attaches to the container;
|
|
|
|
```console
|
|
$ docker run -d --name topdemo alpine top -b
|
|
|
|
$ docker attach topdemo
|
|
|
|
Mem: 2395856K used, 5638884K free, 2328K shrd, 61904K buff, 1524264K cached
|
|
CPU: 0% usr 0% sys 0% nic 99% idle 0% io 0% irq 0% sirq
|
|
Load average: 0.15 0.06 0.01 1/567 6
|
|
PID PPID USER STAT VSZ %VSZ CPU %CPU COMMAND
|
|
1 0 root R 1700 0% 3 0% top -b
|
|
```
|
|
|
|
As the container was started without the `-i`, and `-t` options, signals are
|
|
forwarded to the attached process, which means that the default `CTRL-p CTRL-q`
|
|
detach key sequence produces no effect, but pressing `CTRL-c` terminates the
|
|
container:
|
|
|
|
```console
|
|
<...>
|
|
PID PPID USER STAT VSZ %VSZ CPU %CPU COMMAND
|
|
1 0 root R 1700 0% 7 0% top -b
|
|
^P^Q
|
|
^C
|
|
|
|
$ docker ps -a --filter name=topdemo
|
|
|
|
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
|
|
96254a235bd6 alpine "top -b" 44 seconds ago Exited (130) 8 seconds ago topdemo
|
|
```
|
|
|
|
Repeating the example above, but this time with the `-i` and `-t` options set;
|
|
|
|
```console
|
|
$ docker run -dit --name topdemo2 ubuntu:22.04 /usr/bin/top -b
|
|
```
|
|
|
|
Now, when attaching to the container, and pressing the `CTRL-p CTRL-q` ("read
|
|
escape sequence"), the Docker CLI is handling the detach sequence, and the
|
|
`attach` command is detached from the container. Checking the container's status
|
|
with `docker ps` shows that the container is still running in the background:
|
|
|
|
```console
|
|
$ docker attach topdemo2
|
|
|
|
Mem: 2405344K used, 5629396K free, 2512K shrd, 65100K buff, 1524952K cached
|
|
CPU: 0% usr 0% sys 0% nic 99% idle 0% io 0% irq 0% sirq
|
|
Load average: 0.12 0.12 0.05 1/594 6
|
|
PID PPID USER STAT VSZ %VSZ CPU %CPU COMMAND
|
|
1 0 root R 1700 0% 3 0% top -b
|
|
read escape sequence
|
|
|
|
$ docker ps -a --filter name=topdemo2
|
|
|
|
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
|
|
fde88b83c2c2 alpine "top -b" 22 seconds ago Up 21 seconds topdemo2
|
|
```
|
|
|
|
### 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:
|
|
|
|
```console
|
|
$ docker run --name test -dit alpine
|
|
275c44472aebd77c926d4527885bb09f2f6db21d878c75f0a1c212c03d3bcfab
|
|
|
|
$ docker attach test
|
|
/# exit 13
|
|
|
|
$ echo $?
|
|
13
|
|
|
|
$ docker ps -a --filter name=test
|
|
|
|
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
|
|
a2fe3fd886db alpine "/bin/sh" About a minute ago Exited (13) 40 seconds ago test
|
|
```
|
|
|
|
### <a name="detach-keys"></a> Override the detach sequence (--detach-keys)
|
|
|
|
Use the `--detach-keys` option to 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](https://docs.docker.com/engine/reference/commandline/cli/#configuration-files).
|