= Interactive Use of Docker =

While Docker is primarily intended as a management system for containerized services, it can also be used for interactive utilities.

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== Ephemeral Containers ==

To run an ephemeral container interactively, try:

{{{
docker run --interactive --tty --rm alpine:latest
}}}

The container will be cleaned up once it stops running.

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== Running Containers ==

To open a shell with a running container, try:

{{{
docker exec --interactive --tty my-container /bin/sh
}}}

A different shell binary can be used, but many images are purposefully slimmed down and will not have anything other than [[Shell|sh(1)]] installed.

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== Copying Files ==

It is possible to pass data in and out of containers with pipes.

Some documents recommend using something like the below for copying files from a container.

{{{
docker run --rm httpd:2.4 cat /usr/local/apache2/conf/httpd.conf > my-httpd.conf
}}}

Instead, consider using `docker cp`.

{{{
docker cp my-container:/path/to/container/file /path/to/destination/file
docker cp /path/to/host/file my-container:/path/to/destination/file
}}}

`docker cp` generally behaves like `cp` would, but it should be noted that it internally uses a `tar(1)` stream.

{{{
docker cp my-container:/path/to/container/file /path/to/destination/directory/
docker cp my-container:/path/to/container/directory/ /path/to/destination/directory/
docker cp my-container:/path/to/container/file - | tar x --to-stdout | grep "ERROR"
}}}

Note how `-` is used to indicate that `STDOUT` is the destination.

The former strategy can still be useful in certain circumstances:

{{{
docker exec my-container tar -C /path/to/container/data/directory -czf directory-to-be-archived > /path/to/backup.tar.gz
docker exec my-container tar -C /path/to/container/data/directory -czf directory-to-be-archived | gpg --symmetric --output /path/to/backup.tar.gz.gpg
}}}



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