Asked  6 Months ago    Answers:  5   Viewed   38 times

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?



In order to copy a file from a container to the host, you can use the command

docker cp <containerId>:/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>8000/tcp,>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 .
Tuesday, June 1, 2021
answered 6 Months ago

AppArmor (Application Armor) is a Linux security module that protects an operating system and its applications from security threats. To use it, a system administrator associates an AppArmor security profile with each program. Docker expects to find an AppArmor policy loaded and enforced. Check default profiles with:

# sudo apparmor_status

To use docker default profile on a container, run:

$ docker run --rm -it --name test-container --security-opt apparmor=docker-default image-name

You disable it using the commands:

--security-opt apparmor=unconfined

With the docker run commands.

To disable apparmor service, use:

# systemctl stop apparmor && systemctl disable apparmor

For Ubuntu 14. Use:

# service apparmor stop
# update-rc.d -f apparmor remove

It’s recommended to set working profiles for Docker apparmor than disabling it, especially for production setups.

Check this awesome google document on Securing Containers with AppArmor.

Tuesday, July 27, 2021
answered 4 Months ago

That Docker Hub history view doesn't show the actual Dockerfile; instead, it shows content essentially extracted from the docker history of the image. That doesn't preserve the specific details you're looking for: it doesn't remember the names of base images, or the build-context file names of things that get ADDed or COPYed in.

Chasing through GitHub and Docker Hub links, the golang:*-buster Dockerfile is built FROM buildpack-deps:...-scm; buildpack-deps:buster-scm is FROM buildpack-deps:buster-curl; that is FROM debian:buster; and that has a very simple Dockerfile (quoted here in its entirety):

FROM scratch
ADD rootfs.tar.xz /
CMD ["bash"]

FROM scratch starts from a completely totally empty image; that is the base of the Docker image tree (and what tells docker history and similar tools to stop). The ADD line unpacks a tar file of a Debian system image.

If you look at docker history or the Docker Hub history view you cite, you should be able to see these same steps happening. The ADD file:4b0... in / corresponds to the ADD rootfs.tar.gz /, and the second line is the CMD ["bash"]. It is not split up by Dockerfile or image, and the original filenames from ADD aren't saved. (You couldn't reproduce the image anyways without the contents of the rootfs.tar.gz, so it's merely slightly helpful to know its filename but not essential.)

The ADD file:hash in /path syntax is not standard Dockerfile syntax (the word in in particular is not part of it). I'm not sure there's a reliable way to translate from the host file or URL to the hash, but building the image and looking at its docker history would tell you (assuming you've got a perfect match for the file metadata). There's no way to get back to the original filename or syntax, and definitely no way to get back to the file contents.

Monday, October 11, 2021
answered 2 Months ago

The solution is:

func writeDb(dbName string) {
var mysqldumpPath string = "/usr/bin/mysqldump"
cmd := exec.Command("docker", "exec", "some-mysql", mysqldumpPath, "-u", fmt.Sprintf("%s", USER), fmt.Sprintf("-p%s", PASSWORD) , fmt.Sprintf("%s", dbName))

stdout, err := cmd.StdoutPipe()
if err != nil {

if err := cmd.Start(); err != nil {

bytes, err := ioutil.ReadAll(stdout)
if err != nil {
err = ioutil.WriteFile("./backup/" + dbName +".sql", bytes, 0644)
if err != nil {


Just without "> dbname.sql"

Tuesday, October 19, 2021
Elias Van Ootegem
answered 1 Month ago

It seems there is no way yet to use wildcards with the docker cp command

You can create the mongo dump files into a folder inside the container and then copy the folder, as detailed on the other answer here.

If you have a large dataset and/or need to do the operation often, the best way to handle that is to use docker volumes, so you can directly access the files from the container into your host folder without using any other command:

Thursday, October 28, 2021
answered 1 Month ago
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