I have mounted my USB devices to a docker container using docker run --privileged -v /dev/bus/usb:/dev/bus/usb -d ubuntu
Within the container, I would like to delete few files from /dev/bus/usb/
This results in the deletion of files from the host as well, which is not what I want
I would like to delete files from the container, but continue to have them in the host
Is there any way that I can achieve this ?
This is because you are using a shared volume, so when you delete files this action is effective into your container and into the host.
Maybe you can write a little Dockerfile to create an image with a copy of your usb files and not share the volume into the container.
FROM ubuntu
COPY /dev/bus/usb /path/for/your/copy
After that you can compile your image:
docker build -t imagename .
And finally launch it:
docker run -d imagename
Related
I am new to docker volumes, and my use case is the next:
I have two different containers running in the same host, and both need to read/write files from it. Is of my understanding that I should use docker volumes, but before I try that, I want to make sure that i can delete files of the host filesystem, from inside the containers (e.g. using a golang app)
Maybe, you should use docker volumes. It can share the directory between the host and containers. For example, you want to read/write the file in /mnt, you can mount the /mnt to container.
docker run -it -v /mnt:/mnt ubuntu:latest touch /mnt/hello.log
now, /mnt/hello.log was created. And you can edit the file /mnt/hello.log in you host filesystem.
Then,
docker run -it -v /mnt:/mnt ubuntu:latest rm /mnt/hello.log
After the command above, the file /mnt/hello.log will be deleted from inside the container.
Actually, you can delete the file in golang, like this:
os.Remove("/mnt/hello.log")
I'm running a container by sending to docker daemon so it can run a sibling container and in that container I try to run another container and mount a volume to access some data, however in the sibling container, the volume is either empty or the file is converted to a folder...
Running the first container:
$ docker run -v /var/run/docker.sock:/var/run/docker.sock -it example /bin/bash
root#3aa35965846a:/home/node/example# ls some_volume/
test.txt
root#3aa35965846a:/home/node/example# cat some_volume/test.txt
hello
// Running the second container
root#3aa35965846a:/home/node/example# docker run -v /home/node/example/some_volume/:/some_volume/ -it node:10 /bin/bash
root#6a84739fbb92:/# ls /some_volume/
* test.txt
root#6a84739fbb92:/# cat /some_volume/test.txt/
cat: /some_volume/test.txt/: Is a directory
The first time I run the second container the volume is empty, if I try to mount a file directly it is converted to a folder, and after that if I try to mount the folder like the example above, there is only the file I tried to mount earlier and it is a folder.
How is this possible ? If i try to mount a volume outside the first container I don't have any problem, how can I fix this ?
The first path in the docker run -v option is always on the host system. For example, if you
docker run -v /etc:/x busybox cat /x/shadow
it will dump out the host's encrypted password file, regardless of whether you ran this command directly from the host or from a container.
There isn't a way to share an arbitrary directory from one container to another. If the launching container knows something about its own directory structure (in particular that some directory was mounted from a specific host path or named volume) then it can replicate that to the other container, but that's not a generic answer. The other behaviors you're seeing are just a consequence of those directories not existing on the host system.
In general I would advise not using Docker for short-lived processes that principally interact with the outside world through the filesystem. Take whatever program you'd run in the other container, install it in your image's Dockerfile, and run it directly without going through Docker.
If you really can't avoid this workflow, the only thing I've found to work reliably is to docker create the container, docker cp files in, docker start it, and docker wait for it to finish. When it's done, docker cp the result out before docker rm it. That's a kind of painstaking workflow but it gets around the problem of the two containers not sharing any filesystem space.
The use case is that I want to download and image that contains python code files. Assume the image does not have any text editor installed. So i want to mount a drive on host, so that files in the container show up in this host mount and i can use different editors installed on my host to update the code. Saving the changes are to be reflected in the image.
if i run the following >
docker run -v /host/empty/dir:/container/folder/with/code/files -it myimage
the /host/empty/dir is still empty, and browsing the container dir also shows it as empty. What I want is the file contents of /container/folder/with/code/files to show up in /host/empty/dir
Sébastien Helbert answer is correct. But there is still a way to do this in 2 steps.
First run the container to extract the files:
docker run --rm -it myimage
In another terminal, type this command to copy what you want from the container.
docker cp <container_id>:/container/folder/with/code/files /host/empty/dir
Now stop the container. It will be deleted (--rm) when stopped.
Now if you run your original command, it will work as expected.
docker run -v /host/empty/dir:/container/folder/with/code/files -it myimage
There is another way to access the files from within the container without copying it but it's very cumbersome.
Your /host/empty/dir is always empty because the volume binding replaces (overrides) the container folder with your empty host folder. But you can not do the opposite, that is, you take a container folder to replace your host folder.
However, there is a workaround by manually copying the files from your container folder to your host folder. before using them as you have suggested.
For exemple :
run your docker image with a volume maaping between you host folder and a temp folder : docker run -v /host/empty/dir:/some-temp-folder -it myimage
copy your /container/folder/with/code/files content into /some-temp-folder to fill you host folder with you container folder
run you container with a volum mapping on /host/empty/dir but now this folder is no longer empty : run -v /host/empty/dir:/container/folder/with/code/files -it myimage
Note that steps 1 & 2 may be replaced by : Copying files from Docker container to host
I have a docker container which has some data in let's say /opt/files. File A and B. How can I start that container and access these files on my host machine?
I'm using Docker for Windows (Hyper-V). When i start the container with:
docker run -it -v C:/tmp:/opt/files myImage
I see an empty folder on my windows machine and inside of the container. Any new files I create there are of course reflected on both sides but how can I access files that are already in the container (e.g. because they're added in the Dockerfile)?
You can't share from inside container to host. There are two ways to do it
Copy the files from container
docker cp <containerid>:<file_path_inside_container> localpath
Share a folder other than the one where files will be generated
docker run -it -v C:/tmp:/opt/files_temp myImage
Then you get inside the container copy files from /opt/files to /opt/files_temp
Once your container is started, you can copy files inside it to your host.
Use docker cp for this (https://docs.docker.com/engine/reference/commandline/cp/).
Example : docker cp CONTAINER:SRC_PATH DEST_PATH|-
I know this isn't common practice at all.
I'm trying to share a docker image repertory with an host directory.
Usually, you're doing this the reverse way host directory -> docker image directory with
docker run -v /hostdirectory/:/dockerimagedirectory/
Is there any way to get the same inverted result aka the image directory -> hostdirectory ?
You can try to copy the repertory from container then mount it again to be sync with container changes.
docker cp <containerId>:/file/path/within/container /host/path/target
docker run -v /host/path/target:/file/path/within/container