I have a Docker container that I've created simply by installing Docker on Ubuntu and doing:
sudo docker run -i -t ubuntu /bin/bash
I immediately started installing Java and some other tools, spent some time with it, and stopped the container by
exit
Then I wanted to add a volume and realised that this is not as straightforward as I thought it would be. If I use sudo docker -v /somedir run ... then I end up with a fresh new container, so I'd have to install Java and do what I've already done before just to arrive at a container with a mounted volume.
All the documentation about mounting a folder from the host seems to imply that mounting a volume is something that can be done when creating a container. So the only option I have to avoid reconfiguring a new container from scratch is to commit the existing container to a repository and use that as the basis of a new one whilst mounting the volume.
Is this indeed the only way to add a volume to an existing container?
You can commit your existing container (that is create a new image from container’s changes) and then run it with your new mounts.
Example:
$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
5a8f89adeead ubuntu:14.04 "/bin/bash" About a minute ago Exited (0) About a minute ago agitated_newton
$ docker commit 5a8f89adeead newimagename
$ docker run -ti -v "$PWD/somedir":/somedir newimagename /bin/bash
If it's all OK, stop your old container, and use this new one.
You can also commit a container using its name, for example:
docker commit agitated_newton newimagename
That's it :)
We don't have any way to add volume in running container, but to achieve this objective you may use the below commands:
Copy files/folders between a container and the local filesystem:
docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH
docker cp [OPTIONS] SRC_PATH CONTAINER:DEST_PATH
For reference see:
https://docs.docker.com/engine/reference/commandline/cp/
I've successfully mount /home/<user-name> folder of my host to the /mnt folder of the existing (not running) container. You can do it in the following way:
Open configuration file corresponding to the stopped container, which can be found at /var/lib/docker/containers/99d...1fb/config.v2.json (may be config.json for older versions of docker).
Find MountPoints section, which was empty in my case: "MountPoints":{}. Next replace the contents with something like this (you can copy proper contents from another container with proper settings):
"MountPoints":{"/mnt":{"Source":"/home/<user-name>","Destination":"/mnt","RW":true,"Name":"","Driver":"","Type":"bind","Propagation":"rprivate","Spec":{"Type":"bind","Source":"/home/<user-name>","Target":"/mnt"},"SkipMountpointCreation":false}}
or the same (formatted):
"MountPoints": {
"/mnt": {
"Source": "/home/<user-name>",
"Destination": "/mnt",
"RW": true,
"Name": "",
"Driver": "",
"Type": "bind",
"Propagation": "rprivate",
"Spec": {
"Type": "bind",
"Source": "/home/<user-name>",
"Target": "/mnt"
},
"SkipMountpointCreation": false
}
}
Restart the docker service: service docker restart
This works for me with Ubuntu 18.04.1 and Docker 18.09.0
Jérôme Petazzoni has a pretty interesting blog post on how to Attach a volume to a container while it is running. This isn't something that's built into Docker out of the box, but possible to accomplish.
As he also points out
This will not work on filesystems which are not based on block devices.
It will only work if /proc/mounts correctly lists the block device node (which, as we saw above, is not necessarily true).
Also, I only tested this on my local environment; I didn’t even try on a cloud instance or anything like that
YMMV
Unfortunately the switch option to mount a volume is only found in the run command.
docker run --help
-v, --volume list Bind mount a volume (default [])
There is a way you can work around this though so you won't have to reinstall the applications you've already set up on your container.
Export your container
docker container export -o ./myimage.docker mycontainer
Import as an image
docker import ./myimage.docker myimage
Then docker run -i -t -v /somedir --name mycontainer myimage /bin/bash
A note for using Docker Windows containers after I had to look for this problem for a long time!
Condiditions:
Windows 10
Docker Desktop (latest version)
using Docker Windows Container for image microsoft/mssql-server-windows-developer
Problem:
I wanted to mount a host dictionary into my windows container.
Solution as partially discripted here:
create docker container
docker run -d -p 1433:1433 -e sa_password=<STRONG_PASSWORD> -e ACCEPT_EULA=Y microsoft/mssql-server-windows-developer
go to command shell in container
docker exec -it <CONTAINERID> cmd.exe
create DIR
mkdir DirForMount
stop container
docker container stop <CONTAINERID>
commit container
docker commit <CONTAINERID> <NEWIMAGENAME>
delete old container
docker container rm <CONTAINERID>
create new container with new image and volume mounting
docker run -d -p 1433:1433 -e sa_password=<STRONG_PASSWORD> -e ACCEPT_EULA=Y -v C:\DirToMount:C:\DirForMount <NEWIMAGENAME>
After this i solved this problem on docker windows containers.
My answer will be little different. You can stop your container, add the volume and restart it. How to do it, follow the steps.
docker volume create ubuntu-volume
docker stop <container-name>
sudo docker run -i -t --mount source=ubuntu-volume,target=<target-path-in-container> ubuntu /bin/bash
You can stop and remove the container, append the existing volume in a startup script, and restart from the image. If the already existing existing partitions do keep the data, you shouldn't experience any loss of information. This should also work the same way with Dockerfile and Docker composer.
eg (solr image).
(initial script)
#!/bin/sh
docker pull solr:8.5
docker stop my_solr
docker rm solr:8.5
docker create \
--name my_solr \
-v "/XXXX/docker/solr/solrdata":/var/solr \
-p 8983:8983 \
--restart unless-stopped \
--user 1000:1000 \
-e SOLR_HEAP=1g \
--log-opt max-size=10m \
--log-opt max-file=3 \
solr:8.5
docker cp /home/XXXX/docker/solr/XXXXXXXX.jar my_solr:/opt/solr/contrib/dataimporthandler-extras/lib
docker start my_solr
file with the second volume
#!/bin/sh
docker pull solr:8.5
docker stop my_solr
docker rm solr:8.5
docker create \
--name my_solr \
-v "/XXXX/docker/solr/solrdata":/var/solr \
-v "/XXXX/backups/solr_snapshot_folder":/var/solr_snapshots \
-p 8983:8983 \
--restart unless-stopped \
--user 1000:1000 \
-e SOLR_HEAP=1g \
--log-opt max-size=10m \
--log-opt max-file=3 \
solr:8.5
docker cp /home/XXXX/docker/solr/XXXXXXXX.jar my_solr:/opt/solr/contrib/dataimporthandler-extras/lib
docker start my_solr
Use symlink to the already mounted drive:
ln -s Source_path targer_path_which_is_already_mounted_on_the_running_docker
The best way is to copy all the files and folders inside a directory on your local file system by: docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH
SRC_PATH is on container
DEST_PATH is on localhost
Then do docker-compose down attach a volume to the same DEST_PATH and run Docker containers by using docker-compose up -d
Add volume by following in docker-compose.yml
volumes:
- DEST_PATH:SRC_PATH
Related
Is it possible to rename a docker volume? I want to change the volume names of the existing container. I see that config.json and hostconfig.json has the volume details in it.
docker run -di -p 8083:443 -v app_main_db_test_1:/var/lib/pgsql/data -v app_main_conf_test_1:/var/www/ ubuntu
I want to change app_main_db_test_1 to app_main_db and app_main_conf_test_1 to app_main_conf
as far as i know there are no ways of renaming docker volume so far. There is an open github issue, which indicates there is no solution to the topic yet.
But there are a few useful ways how to do so. Since you are saying you use Docker Desktop you could check this comment:
docker volume create --name <new_volume>
docker run --rm -it -v <old_volume>:/from -v <new_volume>:/to alpine ash -c "cd /from ; cp -av . /to"
docker volume rm <old_volume>
Which should do exactly what you are planning to do.
Figured it out. Thanks to this github post.
# Create new Volume for DB and copy files from old volume
docker volume create --name app_main_db
docker run --rm -it -v app_main_db_test_1:/from -v app_main_db:/to alpine ash -c "cd /from ; cp -av . /to"
# Create new Volume for conf and copy files from old volume
docker volume create --name app_main_conf
docker run --rm -it -v app_main_conf_test_1:/from -v app_main_conf:/to alpine ash -c "cd /from ; cp -av . /to"
# Start the container using new volumes
docker run -di -p 8083:443 -v app_main_db:/var/lib/pgsql/data -v app_main_conf:/var/www/ ubuntu
# Delete old volumes
docker volume rm app_main_db_test_1
docker volume rm app_main_conf_test_1
I mounted my secret file secret.json at runtime to a local docker, and while it works, I don't seems to find this volume anywhere.
My docker file looks like this and has no reference to secret:
RUN mkdir ./app
ADD src/python ./app/src/python
ENTRYPOINT ["python"]
Then I ran
docker build -t {MY_IMAGE_NAME} .
docker run -t -v $PATH_TO_SECRET_FILE/:/secrets/secret.json \
-e MY_CREDENTIALS=/secrets/secret.json \
{MY_IMAGE_NAME} ./app/src/python/runner.py
This runs successfully locally but when I do
docker run --entrypoint "ls" {MY_IMAGE_NAME}
I don't see the volume secrets.
Also, if I run
docker volume ls
it doesn't have anything that looks like secrets.
Without environment variable MY_CREDENTIALS the script won't run. So I am sure the secret file is mounted somewhere, but can't figure out where it is. Any idea?
You are actually creating two separate containers with the commands you are running. The first docker run command creates a container from the image you have built with the volume mounted and then the second command creates a new container from the same image but without any volumes (as you don't define any in your command)
I'd suggest you give your container a name like so
docker run -t -v $PATH_TO_SECRET_FILE/:/secrets/secret.json \
-e MY_CREDENTIALS=/secrets/secret.json \
--name my_container {MY_IMAGE_NAME} ./app/src/python/runner.py
and then run exec on that container
docker exec -it my_container sh
I'm trying to backup my volume as described here in the docker documentation: https://docs.docker.com/storage/volumes/#backup-restore-or-migrate-data-volumes
I'm running the command with the path to the volume:
docker run --rm --volumes-from MYCONTAINER -v $(pwd):/backup ubuntu tar cvf /backup/backup.tar /var/lib/docker/volumes/MYCONTAINER_VOLUME
... and also trying with just the name of my volume
docker run --rm --volumes-from MYCONTAINER -v $(pwd):/backup ubuntu tar cvf /backup/backup.tar MYCONTAINER_VOLUME
but no matter what I get an error like: tar: MYCONTAINER_VOLUME: Cannot stat: No such file or directory
This volume was created and linked to the container with docker-compose and its using a local driver for the volume.
When I run docker volume ls I get:
DRIVER VOLUME NAME
local MYCONTAINER_VOLUME
Can someone please tell me what i'm doing wrong with this?
I figured out what the issue was -
The last part of the command should be the path of the volume mounted in the CONTAINER, not the path of the volume on the HOST.
So basically, the formula for this command should be:
docker run --rm --volumes-from MYCONTAINER -v $(pwd):/backup ubuntu tar cvf /backup/MY_BACKUP.tar /PATH/INSIDE/CONTAINER/TO/VOLUME/data
... and this will create MY_BACKUP.tar in the current directory of the HOST.
also, make sure to STOP the container before archiving the volume if its something like postgres like in my case.
Then, to restore the volume if you're using docker-compose (since I had trouble with this too because the documentation isn't specific to preexisting containers / volumes created this way)
1) STOP the container
2) Make sure MY_BACKUP.tar is in the root project directory of the HOST
3) run
docker run --rm --volumes-from MYCONTAINER -v $(pwd):/backup ubuntu bash -c "cd / && tar xvf /backup/MY_BACKUP.tar
4) restart container
Hope this helps someone and I'm certainly open to any ideas to streamline this.
The documentation assume your container does have a volume associated to your container.
Meaning: your container was started with a volume.
Example:
$ docker run -d \
--name devtest \
--mount source=myvol2,target=/app \
nginx:latest
Check at the very least if you do have volumes created with:
docker volume ls
When running Docker, you can mount files and directories using the --volume option. E.g.:
docker run --volume /remote ./local myimage
I'm running a docker image that defines VOLUMESs in the Dockerfile. I need to access a config file that happens to be inside one of the defined volumes. I'd like to have that file "synced" on the host so that I can edit it. I know I could run docker exec ..., but I hope to circumvent that overhead for only editing one file. I found out that the volumes created by the VOLUMES line are stored in /var/lib/docker/volumes/<HASH>/_data.
Using docker inspect I was able to find the directory that is mounted:
docker inspect gitlab-runner | grep -B 1 '"Destination": "/etc/gitlab-runner"' | head -n 1 | cut -d '"' -f 4
Output:
/var/lib/docker/volumes/9c233c085c36380c6c33035222c16e5d061368c5060cc81dda2a9a713a2b2b3b/_data
So the question is:
Is there a way to re-mount volumes defined in an image? OR to somehow get the directory easier than my oneliner above?
EDIT after comments by zeppelin I've tried rebinding the volume with no success:
$ mkdir etc
$ docker run -d --name test1 gitlab/gitlab-runner
$ docker run -d --name test2 -v ~/etc:/etc/gitlab-runner gitlab/gitlab-runner
$ docker exec test1 ls /etc/gitlab-runner/
certs
config.toml
$ docker exec test2 ls /etc/gitlab-runner/
# empty. no files
$ ls etc
# also empty
docker inspect shows correctly that the volume is bound to ~/etc, but the files inside the container at /etc/gitlab-runner/ seem lost.
$ docker run -d --name test1 gitlab/gitlab-runner
$ docker run -d --name test2 -v ~/etc:/etc/gitlab-runner gitlab/gitlab-runner
You've got two different volume types there. One I call an anonymous volume (a very long uuid visible when you run docker volume ls). The second is a host volume or bind mount that maps a directory on the host directly into the container. So each container you spun up is looking at different places.
Anonymous volumes and named volumes (docker run -d -v mydata:/etc/gitlab-runner gitlab/gitlab-runner) get initialized to the contents of the image at that directory location. This initialization only happens when the volume is empty and is mounted into a new container. Host volumes, as you've seen, only get the contents of the host filesystem, even if it's empty at that location.
With that background, the short answer to your question is no, you cannot mount a file inside the container back out to your host. But you can copy the file out with several methods, assuming you don't overlay the source of the file with a host volume mount. With a running container, there's the docker cp command. Personally, I like:
docker run --rm -v ~/etc:/target gitlab/gitlab-runner \
cp -av /etc/gitlab-runner/. /target/.
If you have a named volume with data you want to copy in or out, you can use any image with the tools you need to do the copy:
docker run --rm -v mydata:/source -v ~/etc:/target busybox \
cp -av /source/. /target/.
Try to avoid modifying data inside a container from the host directly, much nicer is when you wrap your task into another container that you then start with "--volumes-from" option when possible in your case.
Not sure I understood your problem, anyway, as for the documentation you mention,
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. [...] The docker run command initializes the newly
created volume with any data that exists at the specified location
within the base image.
So, following the example Dockerfile , after having built the image
docker build -t mytest .
and having the container running
docker run -d -ti --name mytestcontainer mytest /bin/bash
you can access it from the container itself, e.g.
docker exec -ti mytestcontainer ls -l /myvol/greeting
docker exec -ti mytestcontainer cat /myvol/greeting
Hope it helps.
I would like someone to assist me in reading below docker run command
docker run --rm \
--volumes-from myredis \
-v $PWD/backup:/backup \
debian \
cp /data/dump.rdb /backup/
I know it dumps redis, and attaching volume from container myredis into cwd backup. As for the rest of the command I am having trouble interpreting it.
Thanks.
this command is to create a redis's backup you are coping the dump.rdb into the /backup dir on your host.
--rm means remove the container after run, usually it's a good way to clean your env because you can not reuse this container when it finish its work.
debian is the name of the image that you are using.
"cp /data/dump.rdb /backup/" is the command that you are doing inside your container