I modified the mount directory in the docker-compose.yml file. Which command should I use to make the mounted directory effective?
should I use docker-compose restart?
In the past, I used the docker compose restart command.
Related
For automated testing we can't use a DB Docker container with a defined volume. Just wondering if there would be available an "offical" Postgres image with no mounted volume or volume definitions.
Or if someone has a Dockerfile that would create a container without any volume definitions, that would be very helpful to see or try to use one.
Or is there any way to override a defined volume mount and just use datafile inside of to be created Docker container with running DB.
I think you are mixing up volumes and bind mounts.
https://docs.docker.com/storage/
VOLUME Dockerfile command: A volume with the VOLUME command in a Dockerfile is created into the docker area on the host that is /var/lib/docker/volumes/.
I don't think it is possible to run docker without it having access to this directory or it would be not advisable to restrict permission of docker to these directories, these are dockers own directories after all.
So postgres dockerfile has this command in dockerfile, for example: https://github.com/docker-library/postgres/blob/master/15/bullseye/Dockerfile
line 186: VOLUME /var/lib/postgresql/data
This means that the /var/lib/postgresql/data directory that is inside the postgres container will be a VOLUME that will be stored on the host somewhere in /var/lib/docker/volumes/somerandomhashorguid..... in a directory with a random name.
You can also create a volume like this with docker run:
docker run --name mypostgres -e POSTGRES_PASSWORD=password -v /etc postgres:15.1
This way the /etc directory that is inside the container will be stored on the host in the /var/lib/docker/volumes/somerandomhashorguid.....
This volume solution is needed for containers that need extra IO, because the files of the containers (that are not in volumes) are stored in the writeable layer as per the docs: "Writing into a container’s writable layer requires a storage driver to manage the filesystem. The storage driver provides a union filesystem, using the Linux kernel. This extra abstraction reduces performance as compared to using data volumes, which write directly to the host filesystem."
So you could technically remove the VOLUME command from the postgres dockerfile and rebuild the image for yourself and use that image to create your postgres container but it would have lesser performance.
Bind mounts are the type of data storage solution that can be mounted to anywhere on the host filesystem. For example if you would run:
docker run --name mypostgres -e POSTGRES_PASSWORD=password -v /tmp/mypostgresdata:/var/lib/postgresql/data postgres:15.1
(Take not of the -v flag here, there is a colon between the host and the container directory while previously in the volume version of this flag there was no host directory and no colon either.)
then you would have a directory created on your docker host machine /tmp/mypostgresdata and the directory of the container of /var/lib/postgresql/data would be mapped here instead of the docker volumes internal directory /var/lib/docker/volumes/somerandomhashorguid.....
My general rule of thumb would be to use volumes - as in /var/lib/docker/volumes/ - whenever you can and deviate only if really necessary. Bind mounts are not flexible enough to make an image/container portable and the writable container layer has less performance than docker volumes.
You can list docker volumes with docker volume ls but you will not see bind mounted directories here. For that you will need to do docker inspect containername
"You could just copy one of the dockerfiles used by the postgres project, and remove the VOLUME statement. github.com/docker-library/postgres/blob/… –
Nick ODell
Nov 26, 2022 at 18:05"
answered Nick abow.
And that edited Dockerfile would build "almost" Docker Official Image.
I have a running postgreSQL docker container and need to add a volume mount.
I followed the steps from How can I add a volume to an existing Docker container?, (ran docker commit on the container to save it as an image, and spun up another container based on that image with a named volume mounted in). All the data files from the first container are present in /var/lib/postgres/data of the second container.
However, when I try to query this second postgres database, I cannot see any tables that are in the first container. Been trying to fix this for a few days with no luck, am I missing something here (does mounting a volume obscure the existing data in /var/lib/postres/data)?
Commit will not work as there is the volume defined in the Dockerfile.
Volumes are useful in many cases, for example, for running
database-storage. However, since volumes are not 'part' of a
container, it makes containers no longer portable - which seems in
direct conflict with the slogan "Build once... Run anywhere.."
docker commit data container with VOLUME
One option that you can try is copying data folder to host from an existing container and then launch the container with mount path.
docker cp my_db_cotainer:/var/lib/postgresql/data db_data
then start a new container with this path so it will contain the same data as the previous one
docker run -d --name some-postgres -v $PWD/db_data/:/var/lib/postgresql/data postgres
same for mysql
docker cp some-mysql-old:/var/lib/mysql db_backup
docker run --rm --name some-mysql-new -v $PWD/db_backup:/var/lib/mysql -it mysql
I am trying to read a file from server in spark cluster mode using kubernetes, so i put my file on all workers and i mount driver volume using
val conf = new SparkConf().setAppName("sparksetuptest")
.set("spark.kubernetes.driver.volumes.hostPath.host.mount.path", "/file-directory")
Everything works fine here but when i execute it shows that file not found at specific location.
So i mount directory to executor with .set("spark.kubernetes.executor.volumes.hostPath.host.mount.path", "/file-directory")
But now i am not able to execute program it stuck in a never ending process while fetching data.
Please suggest something, so that i can mount my directory with executor and read that file.
this is an example from nfs-example
spark.kubernetes.driver.volumes.nfs.images.options.server=example.com
spark.kubernetes.driver.volumes.nfs.images.options.path=/data
I think you need to declare the path that you want to mount under options.path and the spark.kubernetes.driver.volumes.[VolumeType].[VolumeName].mount.path is the mount path in your container
For example:
If I want to mount /home/lemon/data on the node of k8s to the path /data the docker container with VolumeName exepv, then
conf.set("spark.kubernetes.executor.volumes.hostPath.exepv.mount.path","/data")
conf.set("spark.kubernetes.executor.volumes.hostPath.exepv.options.path", "/home/lemon/data")
after this, you can access the path /data in your executor container
If I have a docker-compose file like:
version: "3"
services:
postgres:
image: postgres:9.4
volumes:
- db-data:/var/lib/db
volumes:
db-data:
... then doing docker-compose up creates a named volume for db-data. Is there a way to remove this volume via docker-compose? If it were an anonymous volume, then docker-compose rm -v postgres would do the trick. But as it stands, I don't know how to remove the db-data volume without reverting to docker commands. It feels like this should be possible from within the docker-compose CLI. Am I missing something?
docker-compose down -v
removes all volumes attached. See the docs
There's no way to target the removal of a specific named volume with the docker-compose cli. Instead this can be achieved using the docker cli. See the docs.
Use docker volume ls to find the name of specific volume.
Remove the volume using docker volume rm VOLUME_NAME. You will need to have stopped and removed containers using the volume.
An example approach:
# Stop and remove container's using the target volume
docker-compose stop NAME_OF_CONTAINER
# We need the force flag, "-f", as the container is still bound to the volume
docker-compose rm -f NAME_OF_CONTAINER
# Next find your volume name in the following list
docker volume ls
# Finally remove the volume
docker volume rm VOLUME_NAME
Jan, 2022 Update:
This removes all the containers, networks, volumes and images defined in the docker-compose.
docker-compose down -v --rmi all
"-v" is for all the volumes
"--rmi all" is for all the images
I had the same issue as you, excepting I wanted to discard the working state of my grafana container while leaving the other containers running, which are running detached (ie. sudo docker-compose up -d). Here's the procedure I've come up with:
sudo docker-compose ps
sudo docker-compose stop grafana
sudo docker-compose rm --force grafana
sudo docker volume rm metricsmonitoring_grafana_data
sudo docker-compose up --force-recreate -d grafana
I don't know (without playing further) how best to determine the name of the docker volume to remove.
This is on docker-compose version 1.18.0
I'm using docker-compose in one of my projects. During development i mount my source directory to a volume in one of my docker services for easy development. At the same time, I have a db service (psql) that mounts a named volume for persistent data storage.
I start by solution and everything is working fine
$ docker-compose up -d
When I check my volumes I see the named and "unnamed" (source volume).
$ docker volume ls
DRIVER VOLUME NAME
local 226ba7af9689c511cb5e6c06ceb36e6c26a75dd9d619360882a1012cdcd25b72
local myproject_data
The problem I experience is that, when I do
$ docker-compose down
...
$ docker volume ls
DRIVER VOLUME NAME
local 226ba7af9689c511cb5e6c06ceb36e6c26a75dd9d619360882a1012cdcd25b72
local myproject_data
both volumes remain. Every time I run
$ docker-compose down
$ docker-compose up -d
a new volume is created for my source mount
$ docker volume ls
DRIVER VOLUME NAME
local 19181286b19c0c3f5b67d7d1f0e3f237c83317816acbdf4223328fdf46046518
local 226ba7af9689c511cb5e6c06ceb36e6c26a75dd9d619360882a1012cdcd25b72
local myproject_data
I know that this will not happen on my deployment server, since it will not mount the source, but is there a way to not make the mounted source persistent?
You can use the --rm option in docker run. To use it with docker-compose you can use
docker-compose rm -v after stopping your containers with docker-compose stop
If you go through the docs about Data volumes , its mentioned that
Data volumes persist even if the container itself is deleted.
So that means, stopping a container will not remove the volumes it created, whether named or anonymous.
Now if you read further down to Removing volumes
A Docker data volume persists after a container is deleted. You can
create named or anonymous volumes. Named volumes have a specific
source form outside the container, for example awesome:/bar. Anonymous
volumes have no specific source. When the container is deleted, you
should instruct the Docker Engine daemon to clean up anonymous
volumes. To do this, use the --rm option, for example:
$ docker run --rm -v /foo -v awesome:/bar busybox top
This command creates an anonymous /foo volume. When the container is
removed, the Docker Engine removes the /foo volume but not the awesome
volume.
Just remove volumes with the down command:
docker-compose down -v