Docker Copying files from Docker container to host

Question

I m thinking of using Docker to build my dependencies on a Continuous Integration  CI  server  so that I don t have to install all the runtimes and libraries on the agents themselves    To achieve this I would need to copy the build artifacts that are built inside the container back into the host  Is that possible

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TLDR     docker run --rm -iv  PWD   host-volume my-image sh -s  lt  lt EOF chown   id -u    id -g  my-artifact tar xz cp -a my-artifact tar xz  host-volume EOF   Description  docker run with a host volume  chown the artifact  cp the artifact to the host volume     docker build -t my-image -  lt  lt EOF  gt  FROM busybox  gt  WORKDIR  workdir  gt  RUN touch foo txt bar txt qux txt  gt  EOF Sending build context to Docker daemon  2 048kB Step 1 3   FROM busybox  --- gt  00f017a8c2a6 Step 2 3   WORKDIR  workdir  --- gt  Using cache  --- gt  36151d97f2c9 Step 3 3   RUN touch foo txt bar txt qux txt  --- gt  Running in a657ed4f5cab  --- gt  4dd197569e44 Removing intermediate container a657ed4f5cab Successfully built 4dd197569e44    docker run --rm -iv  PWD   host-volume my-image sh -s  lt  lt EOF chown -v   id -u    id -g    txt cp -va   txt  host-volume EOF changed ownership of   host-volume bar txt  to 10335 11111 changed ownership of   host-volume qux txt  to 10335 11111 changed ownership of   host-volume foo txt  to 10335 11111  bar txt  - gt    host-volume bar txt   foo txt  - gt    host-volume foo txt   qux txt  - gt    host-volume qux txt     ls -n total 0 -rw-r--r-- 1 10335 11111 0 May  7 18 22 bar txt -rw-r--r-- 1 10335 11111 0 May  7 18 22 foo txt -rw-r--r-- 1 10335 11111 0 May  7 18 22 qux txt   This trick works because the chown invocation within the heredoc the takes   id -u    id -g  values from outside the running container  i e   the docker host   The benefits are    you don t have to docker container run --name or docker container create --name before you don t have to docker container rm after

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Create a path where you want to copy the file and then use   docker run -d -v hostpath dockerimag

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As a more general solution  there s a CloudBees plugin for Jenkins to build inside a Docker container   You can select an image to use from a Docker registry or define a Dockerfile to build and use    It ll mount the workspace into the container as a volume  with appropriate user   set it as your working directory  do whatever commands you request  inside the container   You can also use the docker-workflow plugin  if you prefer code over UI  to do this  with the image inside      command    Basically all of this  baked into your CI CD server and then some

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With the release of Docker 19 03  you can skip creating the container and even building an image  There s an option with BuildKit based builds to change the output destination  You can use this to write the results of the build to your local directory rather than into an image  E g  here s a build of a go binary     ls Dockerfile  go mod  main go    cat Dockerfile FROM golang 1 12-alpine as dev RUN apk add --no-cache git ca-certificates RUN adduser -D appuser WORKDIR  src COPY    src  CMD CGO ENABLED 0 go build -o app    amp  amp    app  FROM dev as build RUN CGO ENABLED 0 go build -o app   USER appuser CMD      app     FROM scratch as release COPY --from build  etc passwd  etc group  etc  COPY --from build  src app  app USER appuser CMD     app     FROM scratch as artifact COPY --from build  src app  app  FROM release   From the above Dockerfile  I m building the artifact stage that only includes the files I want to export  And the newly introduced --output flag lets me write those to a local directory instead of an image  This needs to be performed with the BuildKit engine that ships with 19 03     DOCKER BUILDKIT 1 docker build --target artifact --output type local dest         Building 43 5s  12 12  FINISHED    gt   internal  load build definition from Dockerfile                                                                              0 7s    gt    gt  transferring dockerfile  572B                                                                                              0 0s    gt   internal  load  dockerignore                                                                                                 0 5s    gt    gt  transferring context  2B                                                                                                   0 0s    gt   internal  load metadata for docker io library golang 1 12-alpine                                                             0 9s    gt   dev 1 5  FROM docker io library golang 1 12-alpine sha256 50deab916cce57a792cd88af3479d127a9ec571692a1a9c22109532c0d0499a0  22 5s    gt    gt  resolve docker io library golang 1 12-alpine sha256 50deab916cce57a792cd88af3479d127a9ec571692a1a9c22109532c0d0499a0       0 0s    gt    gt  sha256 1ec62c064901392a6722bb47a377c01a381f4482b1ce094b6d28682b6b6279fd 155B   155B                                        0 3s    gt    gt  sha256 50deab916cce57a792cd88af3479d127a9ec571692a1a9c22109532c0d0499a0 1 65kB   1 65kB                                    0 0s    gt    gt  sha256 2ecd820bec717ec5a8cdc2a1ae04887ed9b46c996f515abc481cac43a12628da 1 36kB   1 36kB                                    0 0s    gt    gt  sha256 6a17089e5a3afc489e5b6c118cd46eda66b2d5361f309d8d4b0dcac268a47b13 3 81kB   3 81kB                                    0 0s    gt    gt  sha256 89d9c30c1d48bac627e5c6cb0d1ed1eec28e7dbdfbcc04712e4c79c0f83faf17 2 79MB   2 79MB                                    0 6s    gt    gt  sha256 8ef94372a977c02d425f12c8cbda5416e372b7a869a6c2b20342c589dba3eae5 301 72kB   301 72kB                                0 4s    gt    gt  sha256 025f14a3d97f92c07a07446e7ea8933b86068d00da9e252cf3277e9347b6fe69 125 33MB   125 33MB                               13 7s    gt    gt  sha256 7047deb9704134ff71c99791be3f6474bb45bc3971dde9257ef9186d7cb156db 125B   125B                                        0 8s    gt    gt  extracting sha256 89d9c30c1d48bac627e5c6cb0d1ed1eec28e7dbdfbcc04712e4c79c0f83faf17                                         0 2s    gt    gt  extracting sha256 8ef94372a977c02d425f12c8cbda5416e372b7a869a6c2b20342c589dba3eae5                                         0 1s    gt    gt  extracting sha256 1ec62c064901392a6722bb47a377c01a381f4482b1ce094b6d28682b6b6279fd                                         0 0s    gt    gt  extracting sha256 025f14a3d97f92c07a07446e7ea8933b86068d00da9e252cf3277e9347b6fe69                                         5 2s    gt    gt  extracting sha256 7047deb9704134ff71c99791be3f6474bb45bc3971dde9257ef9186d7cb156db                                         0 0s    gt   internal  load build context                                                                                                 0 3s    gt    gt  transferring context  2 11kB                                                                                               0 0s    gt   dev 2 5  RUN apk add --no-cache git ca-certificates                                                                          3 8s    gt   dev 3 5  RUN adduser -D appuser                                                                                              1 7s    gt   dev 4 5  WORKDIR  src                                                                                                        0 5s    gt   dev 5 5  COPY    src                                                                                                         0 4s    gt   build 1 1  RUN CGO ENABLED 0 go build -o app                                                                                11 6s    gt   artifact 1 1  COPY --from build  src app  app                                                                                0 5s    gt  exporting to client                                                                                                           0 1s    gt    gt  copying files 10 00MB                                                                                                      0 1s   After the build was complete the app binary was exported     ls Dockerfile  app  go mod  main go      app Ready to receive requests on port 8080   Docker has other options to the --output flag documented in their upstream BuildKit repo  https   github com moby buildkit output

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Mount a  volume  and copy the artifacts into there   mkdir artifacts docker run -i -v   PWD  artifacts  artifacts ubuntu 14 04 sh  lt  lt  COMMANDS       build software here     cp  lt artifact gt   artifacts       copy more artifacts into   artifacts      COMMANDS   Then when the build finishes and the container is no longer running  it has already copied the artifacts from the build into the artifacts directory on the host   Edit  Caveat  When you do this  you may run into problems with the user id of the docker user matching the user id of the current running user  That is  the files in  artifacts will be shown as owned by the user with the UID of the user used inside the docker container  A way around this may be to use the calling user s UID   docker run -i -v   PWD   working dir -w  working dir -u   id -u        ubuntu 14 04 sh  lt  lt  COMMANDS   Since   id -u  owns  working dir  you should be okay running commands here   and having them work  Then copy stuff into  working dir artifacts   COMMANDS

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You do not need to use docker run   You can do it with docker create   From the docs      The docker create command creates a writeable container layer over the specified image and prepares it for running the specified command  The container ID is then printed to STDOUT  This is similar to docker run -d except the container is never started    So  you can do   docker create -ti --name dummy IMAGE NAME bash docker cp dummy  path to file  dest to file docker rm -f dummy   Here  you never start the container  That looked beneficial to me

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I used PowerShell  Admin  with this command   docker cp  container id   container path  error html  C   error html   Example  docker cp ff3a6608467d  var www app error html  C   error html

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docker cp containerId source path destination path  containerId can be obtained from the command docker ps -a source path should be absolute  for example  if the application service directory starts from the app in your docker container the path would be  app some directory file example   docker cp d86844abc129  app server output server-test png C  Users someone Desktop output

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In order to copy a file from a container to the host  you can use the command  docker cp  lt containerId gt   file path within container  host path target   Here s an example     sudo docker cp goofy roentgen  out read jpg     Here goofy roentgen is the container name I got from the following command     sudo docker ps  CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                                            NAMES 1b4ad9311e93        bamos openface        bin bash          33 minutes ago      Up 33 minutes       0 0 0 0 8000- gt 8000 tcp  0 0 0 0 9000- gt 9000 tcp   goofy roentgen   You can also use  part of  the Container ID  The following command is equivalent to the first    sudo docker cp 1b4a  out read jpg

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I am posting this for anyone that is using Docker for Mac  This is what worked for me      mkdir mybackup   local directory on Mac     docker run --rm --volumes-from  lt containerid gt        -v  pwd  mybackup  backup         busybox                          cp  data mydata txt  backup    Note that when I mount using -v that backup directory is automatically created   I hope this is useful to someone someday

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This can also be done in the SDK for example python  If you already have a container built you can lookup the name via console   docker ps -a   name seems to be some concatenation of a scientist and an adjective  i e   relaxed pasteur     Check out help container get archive     Help on method get archive in module docker models containers   get archive path  chunk size 2097152  method of docker models containers Container instance     Retrieve a file or folder from the container in the form of a tar     archive       Args          path  str   Path to the file or folder to retrieve         chunk size  int   The number of bytes returned by each iteration             of the generator  If   None    data will be streamed as it is             received  Default  2 MB      Returns           tuple   First element is a raw tar data stream  Second element is         a dict containing   stat   information on the specified   path         Raises           py class  docker errors APIError              If the server returns an error       Example            gt  gt  gt  f   open    sh bin tar    wb            gt  gt  gt  bits  stat   container get archive   bin sh            gt  gt  gt  print stat            name    sh    size   1075464   mode   493            mtime    2018-10-01T15 37 48-07 00    linkTarget                gt  gt  gt  for chunk in bits                 f write chunk           gt  gt  gt  f close     So then something like this will pull out from the specified path    output  in the container to your host machine and unpack the tar   import docker import os import tarfile    Docker client client   docker from env    container object container   client containers get  relaxed pasteur    setup tar to write bits to f   open os path join os getcwd    output tar    wb    get the bits bits  stat   container get archive   output    write the bits for chunk in bits      f write chunk  f close    unpack tar   tarfile open  output tar   tar extractall   tar close

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If you just want to pull a file from an image  instead of a running container  you can do this   docker run --rm  lt image gt  cat  lt source gt   gt   lt local dest gt   This will bring up the container  write the new file  then remove the container  One drawback  however  is that the file permissions and modified date will not be preserved

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Another good option is first build the container and then run it using the -c flag with the shell interpreter to execute some commads  docker run --rm -i -v  lt host path gt   lt container path gt   lt mydockerimage gt   bin sh -c  cp -r  tmp homework    lt container path gt     The above command does this   -i   run the container in interactive mode  --rm   removed the container after the execution   -v   shared a folder as volume from your host path to the container path   Finally  the  bin sh -c lets you introduce a command as a parameter and that command will copy your homework files to the container path    I hope this additional answer may help you

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sudo docker cp  lt running container id gt   lt full file path in container gt   lt path on local machine gt    Example    sudo docker cp d8a17dfc455f  tests reports  home acbcb Documents abc

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Mount a volume  copy the artifacts  adjust owner id and group id  mkdir artifacts docker run -i --rm -v   PWD  artifacts  mnt artifacts centos 6  bin bash  lt  lt  COMMANDS ls -la  gt   mnt artifacts ls txt echo Changing owner from    id -u     id -g  to   id -u    id -g  chown -R   id -u    id -g   mnt artifacts COMMANDS  EDIT  Note that some of the commands like   id -u  are backslashed and will therefore be processed within the container  while the ones that are not backslashed will be processed by the shell being run in the host machine BEFORE the commands are sent to the container

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Create a data directory on the host system  outside the container  and mount this to a directory visible from inside the container  This places the files in a known location on the host system  and makes it easy for tools and applications on the host system to access the files  docker run -d -v  path to Local host dir  path to docker dir docker image tag

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You can use bind instead of volume if you want to mount only one folder  not create special storage for a container    Build your image with tag    docker build   -t  lt image gt  Run your image and bind current   pwd  directory where app py stores and map it to  root example  inside your container   docker run --mount type bind source    pwd   target  root example   lt image gt  python app py

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docker run -dit --rm IMAGE docker cp CONTAINER SRC PATH DEST PATH   https   docs docker com engine reference commandline run  https   docs docker com engine reference commandline cp

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If you don t have a running container  just an image  and assuming you want to copy just a text file  you could do something like this    docker run the-image cat path to container file txt  gt  path to host file txt

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Most of the answers do not indicate that the container must run before docker cp will work   docker build -t IMAGE TAG   docker run -d IMAGE TAG CONTAINER ID   docker ps -alq    If you do not know the exact file name  you ll need to run  ls    FILE   docker exec CONTAINER ID sh -c  ls  path   zip   docker cp  CONTAINER ID  path to file   docker stop  CONTAINER ID

[docker] Docker: Copying files from Docker container to host

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