mirror of https://github.com/docker/cli.git
doc/reference: update attach reference
Some touch-ups in the attach reference and man-page;
- remove uses of old images (ubuntu 14.04)
- adds some more wording about `-i` and `-t` to use the detach sequence.
- use `--filter` instead of `grep` to list the container, to make the
example more portable.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit 74086bc93b)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This commit is contained in:
Sebastiaan van Stijn
parent
22bbb73a12
commit
ba33d2f29a
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@ -45,12 +45,12 @@ a container and leave it running using the `CTRL-p CTRL-q` key sequence.
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> so.
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It is forbidden to redirect the standard input of a `docker attach` command
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while attaching to a tty-enabled container (i.e.: launched with `-t`).
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while attaching to a TTY-enabled container (using the `-i` and `-t` options).
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While a client is connected to container's stdio using `docker attach`, Docker
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uses a ~1MB memory buffer to maximize the throughput of the application. If
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this buffer is filled, the speed of the API connection will start to have an
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effect on the process output writing speed. This is similar to other
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While a client is connected to container's `stdio` using `docker attach`, Docker
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uses a ~1MB memory buffer to maximize the throughput of the application.
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Once this buffer is full, the speed of the API connection is affected, and so
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this impacts the output process' writing speed. This is similar to other
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applications like SSH. Because of this, it is not recommended to run
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performance critical applications that generate a lot of output in the
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foreground over a slow client connection. Instead, users should use the
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@ -84,45 +84,68 @@ containers, see [**Configuration file** section](cli.md#configuration-files).
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### Attach to and detach from a running container
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The following example starts an ubuntu container running `top` in detached mode,
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then attaches to the container;
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```console
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$ docker run -d --name topdemo ubuntu /usr/bin/top -b
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$ docker run -d --name topdemo ubuntu:22.04 /usr/bin/top -b
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$ docker attach topdemo
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top - 02:05:52 up 3:05, 0 users, load average: 0.01, 0.02, 0.05
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top - 12:27:44 up 3 days, 21:54, 0 users, load average: 0.00, 0.00, 0.00
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Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
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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
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Mem: 373572k total, 355560k used, 18012k free, 27872k buffers
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Swap: 786428k total, 0k used, 786428k free, 221740k cached
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%Cpu(s): 0.1 us, 0.1 sy, 0.0 ni, 99.8 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
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MiB Mem : 3934.3 total, 770.1 free, 674.2 used, 2490.1 buff/cache
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MiB Swap: 1024.0 total, 839.3 free, 184.7 used. 2814.0 avail Mem
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
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1 root 20 0 17200 1116 912 R 0 0.3 0:00.03 top
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
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1 root 20 0 7180 2896 2568 R 0.0 0.1 0:00.02 top
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```
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top - 02:05:55 up 3:05, 0 users, load average: 0.01, 0.02, 0.05
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Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
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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
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Mem: 373572k total, 355244k used, 18328k free, 27872k buffers
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Swap: 786428k total, 0k used, 786428k free, 221776k cached
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As the container was started without the `-i`, and `-t` options, signals are
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forwarded to the attached process, which means that the default `CTRL-p CTRL-q`
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detach key sequence produces no effect, but pressing `CTRL-c` terminates the
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container:
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
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1 root 20 0 17208 1144 932 R 0 0.3 0:00.03 top
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```console
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<...>
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
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1 root 20 0 7180 2896 2568 R 0.0 0.1 0:00.02 top^P^Q
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^C
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$ docker ps -a --filter name=topdemo
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top - 02:05:58 up 3:06, 0 users, load average: 0.01, 0.02, 0.05
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Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
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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
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Mem: 373572k total, 355780k used, 17792k free, 27880k buffers
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Swap: 786428k total, 0k used, 786428k free, 221776k cached
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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4cf0d0ebb079 ubuntu:22.04 "/usr/bin/top -b" About a minute ago Exited (0) About a minute ago topdemo
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```
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
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1 root 20 0 17208 1144 932 R 0 0.3 0:00.03 top
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^C$
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Repeating the example above, but this time with the `-i` and `-t` options set;
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$ echo $?
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0
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$ docker ps -a | grep topdemo
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```console
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$ docker run -dit --name topdemo2 ubuntu:22.04 /usr/bin/top -b
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```
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7998ac8581f9 ubuntu:14.04 "/usr/bin/top -b" 38 seconds ago Exited (0) 21 seconds ago topdemo
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Now, when attaching to the container, and pressing the `CTRL-p CTRL-q` ("read
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escape sequence"), the Docker CLI is handling the detach sequence, and the
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`attach` command is detached from the container. Checking the container's status
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with `docker ps` shows that the container is still running in the background:
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```console
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$ docker attach topdemo2
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top - 12:44:32 up 3 days, 22:11, 0 users, load average: 0.00, 0.00, 0.00
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Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
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%Cpu(s): 50.0 us, 0.0 sy, 0.0 ni, 50.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
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MiB Mem : 3934.3 total, 770.6 free, 672.4 used, 2491.4 buff/cache
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MiB Swap: 1024.0 total, 839.3 free, 184.7 used. 2815.8 avail Mem
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
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1 root 20 0 7180 2776 2452 R 0.0 0.1 0:00.02 topread escape sequence
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$ docker ps -a --filter name=topdemo2
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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b1661dce0fc2 ubuntu:22.04 "/usr/bin/top -b" 2 minutes ago Up 2 minutes topdemo2
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```
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### Get the exit code of the container's command
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@ -131,18 +154,17 @@ And in this second example, you can see the exit code returned by the `bash`
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process is returned by the `docker attach` command to its caller too:
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```console
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$ docker run --name test -d -it debian
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$ docker run --name test -dit alpine
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275c44472aebd77c926d4527885bb09f2f6db21d878c75f0a1c212c03d3bcfab
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$ docker attach test
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root@f38c87f2a42d:/# exit 13
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exit
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/# exit 13
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$ echo $?
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13
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$ docker ps -a | grep test
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$ docker ps -a --filter name=test
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275c44472aeb debian:7 "/bin/bash" 26 seconds ago Exited (13) 17 seconds ago test
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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a2fe3fd886db alpine "/bin/sh" About a minute ago Exited (13) 40 seconds ago test
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```
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@ -11,7 +11,7 @@ configure the key sequence using the **--detach-keys** option or a configuration
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file. See **config-json(5)** for documentation on using a configuration file.
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It is forbidden to redirect the standard input of a **docker attach** command while
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attaching to a tty-enabled container (i.e.: launched with `-t`).
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attaching to a TTY-enabled container (i.e., launched with `-i` and `-t`).
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# Override the detach sequence
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@ -41,12 +41,12 @@ containers, see **docker(1)**.
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## Attaching to a container
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In this example the top command is run inside a container, from an image called
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fedora, in detached mode. The ID from the container is passed into the **docker
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attach** command:
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In this example the top command is run inside a container from an ubuntu image,
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in detached mode, then attaches to it, and then terminates the container
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with `CTRL-c`:
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$ ID=$(sudo docker run -d ubuntu:20.04 /usr/bin/top -b)
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$ sudo docker attach $ID
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$ docker run -d --name topdemo ubuntu:20.04 /usr/bin/top -b
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$ docker attach topdemo
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top - 00:07:01 up 4:54, 0 users, load average: 0.83, 0.91, 0.82
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Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
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%Cpu(s): 2.3 us, 1.6 sy, 0.0 ni, 95.9 id, 0.0 wa, 0.1 hi, 0.1 si, 0.0 st
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@ -55,12 +55,4 @@ attach** command:
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
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1 root 20 0 5976 3256 2828 R 0.0 0.0 0:00.04 top
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top - 00:07:04 up 4:54, 0 users, load average: 0.76, 0.89, 0.81
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Tasks: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
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%Cpu(s): 2.0 us, 1.4 sy, 0.0 ni, 96.5 id, 0.0 wa, 0.1 hi, 0.0 si, 0.0 st
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MiB Mem : 15846.2 total, 5727.5 free, 2594.4 used, 7524.3 buff/cache
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MiB Swap: 16384.0 total, 16384.0 free, 0.0 used. 12095.6 avail Mem
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
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1 root 20 0 5976 3256 2828 R 0.0 0.0 0:00.04 top
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^C
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