We have a docker container with a folder in /usr/local/lib.
From an application in the host system (not in docker), we want to read the files of the container.
We only can find information about the inverse case (mount system file into docker container).
Normally it is not possible. You can however export the filesystem of a container:
docker container export {container_name} > container.tar
You can then investigate that.
Hope this answers your question
Related
Need to know where docker volumes are located when using the docker machine on macOS.
The installation is using boot2docker, so the VM works behind.
Example:
docker volume create test-data
docker inspect shows a path, but where can I find the specific (physical) location?
It’s inside the virtual machine and isn’t directly accessible from the host.
Debug-level commands like docker volume inspect will give you a path, but they really are only for emergency debugging and not for routine use. If you have a way to get a shell in the VM you can see that path, but you really shouldn’t be directly accessing files there, and you shouldn’t be routinely docker inspecting anything.
macOS use a virtual machine it's different to linux where you can access to volumes from /var/lib/docker/volumes.
For macOS you should connect to a VM to find your volumes.
If you use persistent data volumes in Docker, and you want to access them with command-line.
If your docker host is Linux, that’s not a problem; you can find Docker volumes by /var/lib/docker/volumes path.
However, that’s not the case when you use Docker for Mac.
Try to cd /var/lib/docker/volumes from your MacOS terminal, you ‘ll get nothing.
You see, your Mac machine isn’t a real Docker host. Docker for Mac runs a virtual machine and hides it from you to make things simple.
So, to access persistent volumes created by Docker for Mac, you need to connect on that VM.
In order to accomplish this, we need to use a serial terminal on Mac. There’s a terminal application called “screen” that’s going to help us.
We need to “screen into” the Docker driver by executing a command:
screen
~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty
screen ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty
You should see a blank screen, just press Enter , and after a while, you should see a command line prompt
Now you’re inside Docker’s VM and you can cd into volumes dir by typing: cd /var/lib/docker/volumes
Profit, you got there!
If you need to transfer files from your MacOS host into Docker host you can refer to File Sharing
Hope this helps you!
If you have installed docker using snap then volumes are located at:
/var/snap/docker/common/var-lib-docker/volumes/
location of volumes when using docker official install
/var/lib/docker/volumes/
Normally, if you want to "know" where a volume lives, you would want to map a volume to the local filesystem. When you create a named volume you are just allocating "shared" storage. However, if your really need to know, run this command:
docker volume inspect test-data
I have a directory in my Docker container, and I'm trying to make it available locally using -v screenshots:/srv/screenshots in my docker run command but it's not available.
Do I need to add something else to my command?
Host volumes are mapped from the host into the container, not the other way around. This is one way to have persistent storage (so the data don't disappear when the container is re-created).
You can copy the screenshot folder to your host with docker cp and map them in.
You will have your screenshots in the local screenshots folder. Mapping them in with -v screenshots:/srv/screenshots makes them appear in /srv/screenshots in the container, but these files are really on the host.
See: Mount a host directory as data volume
I'm trying create a container to run a program. I'm using a pre configurate image and now I need run the program. However, it's a machine learning program and I need a dataset from my computer to run.
The file is too large to be copied to the container. It would be best if the program running in the container searched the dataset in a local directory of my computer, but I don't know how I can do this.
Is there any way to do this reference with some docker command? Or using Dockerfile?
Yes, you can do this. What you are describing is a bind mount. See https://docs.docker.com/storage/bind-mounts/ for documentation on the subject.
For example, if I want to mount a folder from my home directory into /mnt/mydata in a container, I can do:
docker run -v /Users/andy/mydata:/mnt/mydata myimage
Now, /mnt/mydata inside the container will have access to /Users/andy/mydata on my host.
Keep in mind, if you are using Docker for Mac or Docker for Windows there are specific directories on the host that are allowed by default:
If you are using Docker Machine on Mac or Windows, your Docker Engine daemon has only limited access to your macOS or Windows filesystem. Docker Machine tries to auto-share your /Users (macOS) or C:\Users (Windows) directory. So, you can mount files or directories on macOS using.
Update July 2019:
I've updated the documentation link and naming to be correct. These type of mounts are called "bind mounts". The snippet about Docker for Mac or Windows no longer appears in the documentation but it should still apply. I'm not sure why they removed it (my Docker for Mac still has an explicit list of allowed mounting paths on the host).
I want to know if Docker can run apps installed in host in the container so that I dont need to install the app on each images which wastes the hard disk space.
I know Linux is different since it requires dependencies and packages locally but I wonder if it is possible to use it like in Windows VM.
In Windows Hyper-V, I did this by sharing the network folder containing portable apps with the container and run apps from inside the Windows VM.
Thank you.
You can link a directory on your host containing the executables into your container. Then it will be accessible in the container. To do so, you can use VOLUMES -- Mount a host directory as a data volume and mount a host directory (here: /tmp/foo) into your container (here: /foo) and execute a script called foo.sh in your container's location /foo/foo.sh:
mkdir /tmp/foo
echo -e "#\!/bin/sh\n\necho foo" > /tmp/foo/foo.sh
docker run --rm -v /tmp/foo:/foo alpine sh /foo/foo.sh
=> foo
The same way, you can add binaries from your host to your container... But I do not think that this is intended and should be used, because a container should work as a standalone, isolated "lightweight-VM". You add an unnecessary dependency to your host machine to it, which seems not to be an elegant solution.
I'm new to docker and docker-compose.
I'm trying to run a service using docker-compose on my Raspberry PI. The data this service uses is stored on my NAS and is accessible via samba.
I'm currently using this bash script to launch the container:
sudo mount -t cifs -o user=test,password=test //192.168.0.60/test /mnt/test
docker-compose up --force-recreate -d
Where the docker-compose.yml file simply creates a container from an image and binds it's own local /home/test folder to the /mnt/test folder on the host.
This works perfectly fine, when launched from the script. However, I'd like the container to automatically restart when the host reboots, so I specified 'always' as restart policy. In the case of a reboot then, the container starts automatically without anyone mounting the remote folder, and the service will not work correctly as a result.
What would be the best approach to solve this issue? Should I use a volume driver to mount the remote share (I'm on an ARM architecture, so my choices are limited)? Is there a way to run a shell script on the host when starting the docker-compose process? Should I mount the remote folder from inside the container?
Thanks
What would be the best approach to solve this issue?
As #Frap suggested, use systemd units to manage the mount and the service and the dependencies between them.
This document discusses how you could set up a Samba mount as a systemd unit. Under Raspbian, it should look something like:
[Unit]
Description=Mount Share at boot
After=network-online.target
Before=docker.service
RequiredBy=docker.service
[Mount]
What=//192.168.0.60/test
Where=/mnt/test
Options=credentials=/etc/samba/creds/myshare,rw
Type=cifs
TimeoutSec=30
[Install]
WantedBy=multi-user.target
Place this in /etc/systemd/system/mnt-test.mount, and then:
systemctl enable mnt-test.mount
systemctl start mnt-test.mount
The After=network-online.target line should cause systemd to wait until the network is available before trying to access this share. The Before=docker.service line will cause systemd to only launch docker after this share has been mounted. The RequiredBy=docker.service means that if you start docker.service, this share will be mounted first (if it wasn't already), and that if the mount fails, docker will not start.
This is using a credentials file rather than specifying the username/password in the unit itself; a credentials file would look like:
username=test
password=test
You could just replace the credentials option with username= and password=.
Should I mount the remote folder from inside the container?
A standard Docker container can't mount filesystems. You can create a privileged container (by adding --privileged to the docker run command line), but that's generally a bad idea (because that container now has unrestricted root access to your host).
I finally "solved" my own issue by defining a script to run in the /etc/rc.local file. It will launch the mount and docker-compose up commands on every reboot.
Being just 2 lines of code and not dependent on any particular Unix flavor, it felt to me like the most portable solution, barring a docker-only solution that I was unable to find.
Thanks all for the answers