How to edit Docker container files from the host?

Question

Now that I found a way to expose host files to the container (-v option) I would like to do kind of the opposite:

How can I edit files from a running container with

Answer 1

The following worked for me

docker run -it IMAGE_NAME /bin/bash

eg. my image was called ipython/notebook

docker run -it ipython/notebook /bin/bash

Answer 2

The best way is:

  $ docker cp CONTAINER:FILEPATH LOCALFILEPATH
  $ vi LOCALFILEPATH
  $ docker cp LOCALFILEPATH CONTAINER:FILEPATH

Limitations with $ docker exec: it can only attach to a running container.

Limitations with $ docker run: it will create a new container.

Answer 3

docker run -it -name YOUR_NAME IMAGE_ID /bin/bash

$>vi path_to_file

Answer 4

Here's the script I use:

#!/bin/bash
IFS=$'\n\t'
set -euox pipefail


CNAME="$1"
FILE_PATH="$2"

TMPFILE="$(mktemp)"
docker exec "$CNAME" cat "$FILE_PATH" > "$TMPFILE"
$EDITOR "$TMPFILE"
cat "$TMPFILE" | docker exec -i "$CNAME" sh -c 'cat > '"$FILE_PATH"
rm "$TMPFILE"

and the gist for when I fix it but forget to update this answer: https://gist.github.com/dmohs/b50ea4302b62ebfc4f308a20d3de4213

Answer 5

Whilst it is possible, and the other answers explain how, you should avoid editing files in the Union File System if you can.

Your definition of volumes isn't quite right - it's more about bypassing the Union File System than exposing files on the host. For example, if I do:

$ docker run --name="test" -v /volume-test debian echo "test"

The directory /volume-test inside the container will not be part of the Union File System and instead will exist somewhere on the host. I haven't specified where on the host, as I may not care - I'm not exposing host files, just creating a directory that is shareable between containers and the host. You can find out exactly where it is on the host with:

$ docker inspect -f "{{.Volumes}}" test
map[/volume_test:/var/lib/docker/vfs/dir/b7fff1922e25f0df949e650dfa885dbc304d9d213f703250cf5857446d104895]

If you really need to just make a quick edit to a file to test something, either use docker exec to get a shell in the container and edit directly, or use docker cp to copy the file out, edit on the host and copy back in.

Answer 6

We can use another way to edit files inside working containers (this won't work if container is stoped).

Logic is to:
-)copy file from container to host
-)edit file on host using its host editor
-)copy file back to container

We can do all this steps manualy, but i have written simple bash script to make this easy by one call.

/bin/dmcedit:

#!/bin/sh
set -e

CONTAINER=$1
FILEPATH=$2
BASE=$(basename $FILEPATH)
DIR=$(dirname $FILEPATH)
TMPDIR=/tmp/m_docker_$(date +%s)/

mkdir $TMPDIR
cd $TMPDIR
docker cp $CONTAINER:$FILEPATH ./$DIR
mcedit ./$FILEPATH
docker cp ./$FILEPATH $CONTAINER:$FILEPATH
rm -rf $TMPDIR

echo 'END'
exit 1;

Usage example:

dmcedit CONTAINERNAME /path/to/file/in/container

The script is very easy, but it's working fine for me.

Any suggestions are appreciated.