Related
When using -v switch the files from container should be copied to localhost volume right? But it seems like the directory jenkins_home isn't created at all.
If I create the jenkins_home directory manually and then mount it, the directory is still empty.
I want to preserve the jenkins configs so I could re-run image later.
docker run -p 8080:8080 -p 50000:50000 -d -v jenkins_home:/var/jenkins_home jenkins/jenkins:latest
If you docker run -v jenkins_home:... where the first half of the -v option has no slashes in it at all, that syntax creates a named Docker volume; it isn't a bind mount.
If you docker run -v "$PWD/jenkins_home:..." then that host directory is mounted over the corresponding container directory. At startup time, nothing is ever copied into the host directory; if the host directory is empty, that empty directory gets mounted into the container, hiding everything that was in the image.
If you use the docker run -v named-volume:... syntax, and the named volume is empty, then in this case only, and only the very first time the container is run, the contents of the image are copied into the named volume. This doesn't work for bind mounts, and it doesn't work if there is already data in the volume (perhaps from a previous docker run). It also does not work in other container environments such as Kubernetes. I do not recommend relying on this behavior.
Probably the easiest way to make this work is to launch a one-off container to export the contents of the image, and then use bind-mount syntax:
cd jenkins_home
docker run \
--rm \ # clean up this container when done
-w /var/jenkins_home \ # set the current container directory
jenkins/jenkins \ # the image to run
tar cf - . \ # write a tar file to stdout
| tar xf - # and unpack it on the host
# Now launch the container as normal
docker run -d -p ... -v "$PWD:/var/jenkins_home" jenkins/jenkins
Figured it out.
Turned out that by default it creates the volume in /var/lib/docker/volumes/jenkins_home/ instead of in the current directory.
Also I had tried docker volume create jenkins_home before running the docker image to mount. So not sure if it was the -v jenkins_home:/var/jenkins_home or if it was docker create volume that created the directory in /var/lib/docker/volumes/.
FROM ubuntu:15.04
RUN mkdir -p /app/tina
RUN touch /app/tina/foo.txt
RUN echo "testing tina" > /app/tina/foo.txt
VOLUME /app/tina
CMD sh
As per Docker guide
This Dockerfile results in an image that causes docker run to create a
new mount point at /app/tina and copy the foo.txt file into the newly
created volume
but when I do
docker run --rm -it -v /tmp/foo:/app/tina imagename sh
ls /app/tina/
I can't find foo.txt inside it.
From https://docs.docker.com/engine/reference/builder/#volume
The VOLUME instruction creates a mount point with the specified name and marks it as holding externally mounted volumes from native
host or other containers.
You are using /tmp/foo which is a directory, not a volume. Try:
docker volume create my-vol
docker run --rm -it -v my-vol:/app/tina imagename ls /app/tina/
The problem is that attaching an external directory as a volume using -v actually performs a bind mount: /tmp/foo directory is mounted to the /app/tina directory of the container.
In Linux, when you mount something, all files which were previously seen in the mount point (/app/tina in your case) become invisible. So, when you mount /tmp/foo (empty directory) to /app/tina (which contains foo.txt), the foo.txt file becomes invisible and you see the contents of /tmp/foo in the /app/tina directory, i.e. nothing.
You may ensure that you will see foo.txt in /app/tina when you will unmount tmp/foo from it:
root#84d8cfad500a:/# ls /app/tina
root#84d8cfad500a:/# umount /app/tina
root#84d8cfad500a:/# ls /app/tina
foo.txt
However, this would work only in the privileged (docker run --privileged) container (otherwise you will not be able to unmount /app/tina).
Your files are hidden. This is simply how mounts work. If I were to plug in a flash drive and mount it to ~/someDirectory, then anything in ~/someDirectory would be masked by the files available in the new mount. The volumes feature in docker works the same way.
You can avoid this behavior if you create entrypoint.sh and put these lines into entrypoint
RUN mkdir -p /app/tina
RUN touch /app/tina/foo.txt
RUN echo "testing tina" > /app/tina/foo.txt
when you create container (not image) docker creates volume and after it creates foo.txt and puts "testing tina" to the file.
Of course, don't forget to mention entrypoint in Dockerfile
I was using Docker in the old way, with a volume container:
docker run -d --name jenkins-data jenkins:tag echo "data-only container for Jenkins"
But now I changed to the new way by creating a named volume:
docker volume create --name my-jenkins-volume
I bound this new volume to a new Jenkins container.
The only thing I've left is a folder in which I have the /var/jenkins_home of my previous jenkins container. (by using docker cp)
Now I want to fill my new named volume with the content of that folder.
Can I just copy the content of that folder to /var/lib/jenkins/volume/my-jenkins-volume/_data?
You can certainly copy data directly into /var/lib/docker/volumes/my-jenkins-volume/_data, but by doing this you are:
Relying on physical access to the docker host. This technique won't work if you're interacting with a remote docker api.
Relying on a particular aspect of the volume implementation would could change in the future, breaking any processes you have that rely on it.
I think you are better off relying on things you can accomplish using the docker api, via the command line client. The easiest solution is probably just to use a helper container, something like:
docker run -v my-jenkins-volume:/data --name helper busybox true
docker cp . helper:/data
docker rm helper
You don't need to start some container to add data to already existing named volume, just create a container and copy data there:
docker container create --name temp -v my-jenkins-volume:/data busybox
docker cp . temp:/data
docker rm temp
You can reduce the accepted answer to one line using, e.g.
docker run --rm -v `pwd`:/src -v my-jenkins-volume:/data busybox cp -r /src /data
Here are steps for copying contents of ~/data to docker volume named my-vol
Step 1. Attach the volume to a "temporary" container. For that run in terminal this command :
docker run --rm -it --name alpine --mount type=volume,source=my-vol,target=/data alpine
Step 2. Copy contents of ~/data into my-vol . For that run this commands in new terminal window :
cd ~/data
docker cp . alpine:/data
This will copy contents of ~/data into my-vol volume. After copy exit the temporary container.
You can add this BASH function to your .bashrc to copy files to a existing Docker volume without running a container
# Usage: copy-to-docker-volume SRC_PATH DEST_VOLUME_NAME [DEST_PATH]
copy-to-docker-volume() {
SRC_PATH=$1
DEST_VOLUME_NAME=$2
DEST_PATH="${3:-}"
# create smallest Docker image possible
echo -e 'FROM scratch\nLABEL empty=""' | docker build -t empty -
# create temporary container to be able to mount volume
CONTAINER_ID=$(docker container create -v my-volume:/data empty cmd)
# copy files to volume
docker cp "${SRC_PATH}" "${CONTAINER_ID}":"/data/${DEST_PATH}"
# remove temporary container
docker rm "${CONTAINER_ID}"
}
Example
# create volume as destination
docker volume create my-volume
# create directory to copy
mkdir my-dir
echo "hello file1" > my-dir/my-file-1
# copy directory to volume
copy-to-docker-volume my-dir my-volume
# list directory on volume
docker run --rm -it -v my-volume:/data busybox ls -la /data/my-dir
# show file content on volume
docker run --rm -it -v my-volume:/data busybox cat /data/my-dir/my-file-1
# create another file to copy
echo "hello file2" > my-file-2
# copy file to directory on volume
copy-to-docker-volume my-file-2 my-volume my-dir
# list (updated) directory on volume
docker run --rm -it -v my-volume:/data busybox ls -la /data/my-dir
# check volume content
docker run --rm -it -v my-volume:/data busybox cat /data/my-dir/my-file-2
If you don't want to create a docker and you can access as privileged user to , simply do (on Linux systems):
docker volume create my_named_volume
sudo cp -p . /var/lib/docker/volumes/my_named_volume/_data/
Furthermore, it also allows you to access data in docker runtime or also with docker containers stopped.
If you don't want to create a temp helper container on windows docker desktop (backed by wsl2) then
copy the files to below location
\\wsl$\docker-desktop-data\version-pack-data\community\docker\volumes\my-volume\_data
here my-volume is the name of your named volume. browse the above path from address bar in your file explorer. This is a internal network created by wsl in windows.
Note: it might be better to use docker API like mentioned by larsks, but I have not faced any issues on windows.
Similarly on linux files can be copied to
/var/lib/docker/volumes/my-volume/_data/
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 a host editor?
sshfs could probably do the job but since a running container is already some kind of host directory I wonder if there is a portable (between aufs, btrfs and device mapper) way to do that?
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.
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.
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 $TMPDIR
echo 'END'
exit 1;
Usage example:
dmcedit CONTAINERNAME /path/to/file/in/container
The script is very easy, but it's working fine for me.
Any suggestions are appreciated.
There are two ways to mount files into your container. It looks like you want a bind mount.
Bind Mounts
This mounts local files directly into the container's filesystem. The containerside path and the hostside path both point to the same file. Edits made from either side will show up on both sides.
mount the file:
❯ echo foo > ./foo
❯ docker run --mount type=bind,source=$(pwd)/foo,target=/foo -it debian:latest
# cat /foo
foo # local file shows up in container
in a separate shell, edit the file:
❯ echo 'bar' > ./foo # make a hostside change
back in the container:
# cat /foo
bar # the hostside change shows up
# echo baz > /foo # make a containerside change
# exit
❯ cat foo
baz # the containerside change shows up
Volume Mounts
mount the volume
❯ docker run --mount type=volume,source=foovolume,target=/foo -it debian:latest
root#containerB# echo 'this is in a volume' > /foo/data
the local filesystem is unchanged
docker sees a new volume:
❯ docker volume ls
DRIVER VOLUME NAME
local foovolume
create a new container with the same volume
❯ docker run --mount type=volume,source=foovolume,target=/foo -it debian:latest
root#containerC:/# cat /foo/data
this is in a volume # data is still available
syntax: -v vs --mount
These do the same thing. -v is more concise, --mount is more explicit.
bind mounts
-v /hostside/path:/containerside/path
--mount type=bind,source=/hostside/path,target=/containerside/path
volume mounts
-v /containerside/path
-v volumename:/containerside/path
--mount type=volume,source=volumename,target=/containerside/path
(If a volume name is not specified, a random one is chosen.)
The documentaion tries to convince you to use one thing in favor of another instead of just telling you how it works, which is confusing.
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
If you think your volume is a "network drive", it will be easier.
To edit the file located in this drive, you just need to turn on another machine and connect to this network drive, then edit the file like normal.
How to do that purely with docker (without FTP/SSH ...)?
Run a container that has an editor (VI, Emacs). Search Docker hub for "alpine vim"
Example:
docker run -d --name shared_vim_editor \
-v <your_volume>:/home/developer/workspace \
jare/vim-bundle:latest
Run the interactive command:
docker exec -it -u root shared_vim_editor /bin/bash
Hope this helps.
I use sftp plugin from my IDE.
Install ssh server for your container and allow root access.
Run your docker container with -p localport:22
Install from your IDE a sftp plugin
Example using sublime sftp plugin:
https://www.youtube.com/watch?v=HMfjt_YMru0
The way I am doing is using Emacs with docker package installed. I would recommend Spacemacs version of Emacs. I would follow the following steps:
1) Install Emacs (Instruction) and install Spacemacs (Instruction)
2) Add docker in your .spacemacs file
3) Start Emacs
4) Find file (SPC+f+f) and type /docker:<container-id>:/<path of dir/file in the container>
5) Now your emacs will use the container environment to edit the files
docker run -it -name YOUR_NAME IMAGE_ID /bin/bash
$>vi path_to_file
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
I am trying to build a backup and restore solution for the Docker containers that we work with.
I have Docker base image that I have created, ubuntu:base, and do not want have to rebuild it each time with a Docker file to add files to it.
I want to create a script that runs from the host machine and creates a new container using the ubuntu:base Docker image and then copies files into that container.
How can I copy files from the host to the container?
The cp command can be used to copy files.
One specific file can be copied TO the container like:
docker cp foo.txt container_id:/foo.txt
One specific file can be copied FROM the container like:
docker cp container_id:/foo.txt foo.txt
For emphasis, container_id is a container ID, not an image ID. (Use docker ps to view listing which includes container_ids.)
Multiple files contained by the folder src can be copied into the target folder using:
docker cp src/. container_id:/target
docker cp container_id:/src/. target
Reference: Docker CLI docs for cp
In Docker versions prior to 1.8 it was only possible to copy files from a container to the host. Not from the host to a container.
Get container name or short container id:
$ docker ps
Get full container id:
$ docker inspect -f '{{.Id}}' SHORT_CONTAINER_ID-or-CONTAINER_NAME
Copy file:
$ sudo cp path-file-host /var/lib/docker/aufs/mnt/FULL_CONTAINER_ID/PATH-NEW-FILE
EXAMPLE:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d8e703d7e303 solidleon/ssh:latest /usr/sbin/sshd -D cranky_pare
$ docker inspect -f '{{.Id}}' cranky_pare
or
$ docker inspect -f '{{.Id}}' d8e703d7e303
d8e703d7e3039a6df6d01bd7fb58d1882e592a85059eb16c4b83cf91847f88e5
$ sudo cp file.txt /var/lib/docker/aufs/mnt/**d8e703d7e3039a6df6d01bd7fb58d1882e592a85059eb16c4b83cf91847f88e5**/root/file.txt
The cleanest way is to mount a host directory on the container when starting the container:
{host} docker run -v /path/to/hostdir:/mnt --name my_container my_image
{host} docker exec -it my_container bash
{container} cp /mnt/sourcefile /path/to/destfile
Typically there are three types:
From a container to the host
docker cp container_id:./bar/foo.txt .
Also docker cp command works both ways too.
From the host to a container
docker exec -i container_id sh -c 'cat > ./bar/foo.txt' < ./foo.txt
Second approach to copy from host to container:
docker cp foo.txt mycontainer:/foo.txt
From a container to a container mixes 1 and 2
docker cp container_id1:./bar/foo.txt .
docker exec -i container_id2 sh -c 'cat > ./bar/foo.txt' < ./foo.txt
The following is a fairly ugly way of doing it but it works.
docker run -i ubuntu /bin/bash -c 'cat > file' < file
If you need to do this on a running container you can use docker exec (added in 1.3).
First, find the container's name or ID:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b9b7400ddd8f ubuntu:latest "/bin/bash" 2 seconds ago Up 2 seconds elated_hodgkin
In the example above we can either use b9b7400ddd8f or elated_hodgkin.
If you wanted to copy everything in /tmp/somefiles on the host to /var/www in the container:
$ cd /tmp/somefiles
$ tar -cv * | docker exec -i elated_hodgkin tar x -C /var/www
We can then exec /bin/bash in the container and verify it worked:
$ docker exec -it elated_hodgkin /bin/bash
root#b9b7400ddd8f:/# ls /var/www
file1 file2
Create a new dockerfile and use the existing image as your base.
FROM myName/myImage:latest
ADD myFile.py bin/myFile.py
Then build the container:
docker build .
The solution is given below,
From the Docker shell,
root#123abc:/root# <-- get the container ID
From the host
cp thefile.txt /var/lib/docker/devicemapper/mnt/123abc<bunch-o-hex>/rootfs/root
The file shall be directly copied to the location where the container sits on the filesystem.
Another solution for copying files into a running container is using tar:
tar -c foo.sh | docker exec -i theDockerContainer /bin/tar -C /tmp -x
Copies the file foo.sh into /tmp of the container.
Edit: Remove reduntant -f, thanks to Maartens comment.
To copy a file from host to running container
docker exec -i $CONTAINER /bin/bash -c "cat > $CONTAINER_PATH" < $HOST_PATH
Based on Erik's answer and Mikl's and z0r's comments.
This is a direct answer to the question 'Copying files from host to Docker container' raised in this question in the title.
Try docker cp. It is the easiest way to do that and works even on my Mac. Usage:
docker cp /root/some-file.txt some-docker-container:/root
This will copy the file some-file.txt in the directory /root on your host machine into the Docker container named some-docker-container into the directory /root. It is very close to the secure copy syntax. And as shown in the previous post, you can use it vice versa. I.e., you also copy files from the container to the host.
And before you downlink this post, please enter docker cp --help. Reading the documentation can be very helpful, sometimes...
If you don't like that way and you want data volumes in your already created and running container, then recreation is your only option today. See also How can I add a volume to an existing Docker container?.
I tried most of the (upvoted) solutions here but in docker 17.09 (in 2018) there is no longer /var/lib/docker/aufs folder.
This simple docker cp solved this task.
docker cp c:\path\to\local\file container_name:/path/to/target/dir/
How to get container_name?
docker ps
There is a NAMES section. Don't use aIMAGE.
With Docker 1.8, docker cp is able to copy files from host to container. See the Docker blog post Announcing Docker 1.8: Content Trust, Toolbox, and Updates to Registry and Orchestration.
To copy files/folders between a container and the local filesystem, type the command:
docker cp {SOURCE_FILE} {DESTINATION_CONTAINER_ID}:/{DESTINATION_PATH}
For example,
docker cp /home/foo container-id:/home/dir
To get the contianer id, type the given command:
docker ps
The above content is taken from docker.com.
Assuming the container is already running, type the given command:
# cat /path/to/host/file/ | docker exec -i -t <container_id> bash -c "/bin/cat > /path/to/container/file"
To share files using shared directory, run the container by typing the given command:
# docker run -v /path/to/host/dir:/path/to/container/dir ...
Note: Problems with permissions might arise as container's users are not the same as the host's users.
This is the command to copy data from Docker to Host:
docker cp container_id:file path/filename /hostpath
docker cp a13fb9c9e674:/tmp/dgController.log /tmp/
Below is the command to copy data from host to docker:
docker cp a.txt ccfbeb35116b:/home/
Container Up Syntax:
docker run -v /HOST/folder:/Container/floder
In docker File
COPY hom* /myFolder/ # adds all files starting with "hom"
COPY hom?.txt /myFolder/ # ? is replaced with any single character, e.g., "home.txt"
In a docker environment, all containers are found in the directory:
/var/lib/docker/aufs/required-docker-id/
To copy the source directory/file to any part of the container, type the given command:
sudo cp -r mydir/ /var/lib/docker/aufs/mnt/required-docker-id/mnt/
Docker cp command is a handy utility that allows to copy files and folders between a container and the host system.
If you want to copy files from your host system to the container, you should use docker cp command like this:
docker cp host_source_path container:destination_path
List your running containers first using docker ps command:
abhishek#linuxhandbook:~$ sudo docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS
PORTS NAMES
8353c6f43fba 775349758637 "bash" 8 seconds ago Up 7
seconds ubu_container
You need to know either the container ID or the container name. In my case, the docker container name is ubu_container. and the container ID is 8353c6f43fba.
If you want to verify that the files have been copied successfully, you can enter your container in the following manner and then use regular Linux commands:
docker exec -it ubu_container bash
Copy files from host system to docker container
Copying with docker cp is similar to the copy command in Linux.
I am going to copy a file named a.py to the home/dir1 directory in the container.
docker cp a.py ubu_container:/home/dir1
If the file is successfully copied, you won’t see any output on the screen. If the destination path doesn’t exist, you would see an error:
abhishek#linuxhandbook:~$ sudo docker cp a.txt ubu_container:/home/dir2/subsub
Error: No such container:path: ubu_container:/home/dir2
If the destination file already exists, it will be overwritten without any warning.
You may also use container ID instead of the container name:
docker cp a.py 8353c6f43fba:/home/dir1
If the host is CentOS or Fedora, there is a proxy NOT in /var/lib/docker/aufs, but it is under /proc:
cp -r /home/user/mydata/* /proc/$(docker inspect --format "{{.State.Pid}}" <containerid>)/root
This cmd will copy all contents of data directory to / of container with id "containerid".
docker cp [OPTIONS] SRC_PATH CONTAINER:DEST_PATH
The destination path must be pre-exist
tar and docker cp are a good combo for copying everything in a directory.
Create a data volume container
docker create --name dvc --volume /path/on/container cirros
To preserve the directory hierarchy
tar -c -C /path/on/local/machine . | docker cp - dvc:/path/on/container
Check your work
docker run --rm --volumes-from dvc cirros ls -al /path/on/container
Many that find this question may actually have the problem of copying files into a Docker image while it is being created (I did).
In that case, you can use the COPY command in the Dockerfile that you use to create the image.
See the documentation.
In case it is not clear to someone like me what mycontainer in #h3nrik answer means, it is actually the container id. To copy a file WarpSquare.mp4 in /app/example_scenes/1440p60 from an exited docker container to current folder I used this.
docker cp `docker ps -q -l`:/app/example_scenes/1440p60/WarpSquare.mp4 .
where docker ps -q -l pulls up the container id of the last exited instance. In case it is not an exited container you can get it by docker container ls or docker ps
docker cp SRC_PATH CONTAINER_ID:DEST_PATH
For example, I want to copy my file xxxx/download/jenkins to tomcat
I start to get the id of the container Tomcat
docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
63686740b488 tomcat "catalina.sh run" 12 seconds ago Up 11 seconds 0.0.0.0:8080->8080/tcp peaceful_babbage
docker cp xxxx/download/jenkins.war 63686740b488:usr/local/tomcat/webapps/
This is a onliner for copying a single file while running a tomcat container.
docker run -v /PATH_TO_WAR/sample.war:/usr/local/tomcat/webapps/myapp.war -it -p 8080:8080 tomcat
This will copy the war file to webapps directory and get your app running in no time.
My favorite method:
CONTAINERS:
CONTAINER_ID=$(docker ps | grep <string> | awk '{ print $1 }' | xargs docker inspect -f '{{.Id}}')
file.txt
mv -f file.txt /var/lib/docker/devicemapper/mnt/$CONTAINER_ID/rootfs/root/file.txt
or
mv -f file.txt /var/lib/docker/aufs/mnt/$CONTAINER_ID/rootfs/root/file.txt
The best way for copying files to the container I found is mounting a directory on host using -v option of docker run command.
There are good answers, but too specific. I find out docker ps is good way to get container id you're interested in. Then do
mount | grep <id>
to see where the volume is mounted. That's
/var/lib/docker/devicemapper/mnt/<id>/rootfs/
for me, but it might be a different path depending on the OS and configuration. Now simply copy files to that path.
Using -v is not always practical.
Try docker cp.
Usage:
docker cp CONTAINER:PATH HOSTPATH
It copies files/folders from PATH to the HOSTPATH.