this command adding 50G to existing container or it's create container?
vzctl set 111 --diskspace 50G:50G --save
your command is setting the soft- and hard- diskspacelimit of the existing container: 111 to 50G.
For creating a container use vzctl create or prlctl create.
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.
If there is a running docker-compose stack, is it possible to find out what location (aka workdir) was used to launch the containers?
Let's assume the docker-compose.yml was moved or deleted afterward so find isn't reliable.
For context, here's what happens when running docker-compose up -d with the same file from a different location:
Creating redis ...
Creating solr ...
Creating mysql ...
ERROR: for redis-db Cannot create container for service redis-db: Conflict. The container name "/redis" is already in use by container "48b96cac70369b24a31435c34ba34a34306fd395c6412fc71b4f64f79d708b39". You have to remove (or rename) that container to be able to reuse that name.
ERROR: for mysql-db Cannot create container for service mysql-db: Conflict. The container name "/mysql" is already in use by container "cb32c60caed4b225f082a4ddb22f527e815c94a59c5ced32a1b9bb7234aa96cb". You have to remove (or rename) that container to be able to reuse that name.
ERROR: for solr-server Cannot create container for service solr-server: Conflict. The container name "/solr" is already in use by container "91fe8d364f4f42e00d89d69be46ae01315a0753d81dfd9288ee6caa308b4ebf9". You have to remove (or rename) that container to be able to reuse that name.
Encountered errors while bringing up the project.
I'm very new to using docker and I've created a postgres container using
docker run --name mytrainingdb -e POSTGRES_PASSWORD=mysecretpassword -d postgres. Then I connected to it with docker exec -it <container-id> bash and then psql.
Then I stop the container.
My query is, what do I do reconnect to the same database? I tried to run same docker run command, but it says the name 'mytrainingdb' is used, which means it is trying to create it afresh, which is not what I want. Hope my expectation is right, as in when I restart my laptop or resume work I can just restart the same container and my data/config would be preserved?
The documentation also mentions that we can link a host directory to volume of pg container to have the stored data accessible to us, but I'm ok with docker managing my storage for that database.
You will have error when you try to re-run the same command, because docker is trying to create a new container with same name as the previous one "mytrainingdb". If you close docker and reopen it you will still find your container , but its not running , you can start it again with docker start mytrainingdb or you can remove it with docker rm mytrainingdb .
However , dont restart docker because you want to create a new container with the same name! If you want to start a new container with the same name and your container is still running you can first stop it with docker stop mytrainingdb and docker rm mytrainingdb or you can just do docker rm -f mytrainingdb (this will remove you running container with force ) and then create a new container..
As for the volumes ,you just created one by default which is named is kind of hash , and its found at volumes/var/lib/docker/volumes/ .Because generally containers such PostgreSQL, or databases in general persists volumes. The volume gets created when running the container and is handy to save persistent data, whether you start the container with -v or not.
The volume you talked about in your question , is called mounted volume , is when you basically just bind a certain directory or file from the host (outside) to inside the container
docker run -v /hostdir:/containerdir in your case docker run -v /hostdir:/var/lib/postgresql/data
If you restart docker or your computer running containers won't be automatically restarted. You can start your container again with docker start mytrainingdb (related question), then connect with your docker exec command.
(one tip: instead of running bash, then psql, you can directly run psql, e.g. docker exec -it mytrainingdb psql --user postgres)
Your understanding of data persistence is correct, docker will manage the data and it will still be around.
From the postgres image documentation
There are several ways to store data used by applications that run in Docker containers. We encourage users of the postgres images to familiarize themselves with the options available, including:
Let Docker manage the storage of your database data by writing the database files to disk on the host system using its own internal volume management. This is the default and is easy and fairly transparent to the user. The downside is that the files may be hard to locate for tools and applications that run directly on the host system, i.e. outside containers.
You can add --rm argument so that whenever you stop the container manually, or container stops for any reasons (his task is done or it fails), it will remove that container.
In your case, you can use this:
docker run --name mytrainingdb --rm -e POSTGRES_PASSWORD=mysecretpassword -d postgres
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 have a container called "postgres", build with plain docker command, that has a configured PostgreSQL inside it. Also, I have a docker-compose setup with two services - "api" and "nginx".
How to add the "postgres" container to my existing docker-compose setup as a service, without rebuilding? The PostgreSQL database is configured manually, and filled with data, so rebuilding is a really, really bad option.
I went through the docker-compose documentation, but found no way to do this without a re-build, sadly.
Unfortunately this is not possible.
You don't refer containers on docker-compose, you use images.
You need to create a volume and/or bind mount it to keep your database data.
This is because containers do not save data, if you have filled it with data and did not make a bind mount or a volume to it, you will lose everything on using docker container stop.
Recommendation:
docker cp
Docker cp will copy the contents from container to host. https://docs.docker.com/engine/reference/commandline/container_cp/
Create a folder to save all your PostgreSQL data (ex: /home/user/postgre_data/)
Save the contents of your PostgreSQL container data to this folder (docker hub postgres page for further reference: ;
Run a new PostgreSQL (same version) container with a bind mount poiting to the new folder;
This will maintain all your data and you will be able to volume or bind mount it to use on docker-compose.
Reference of docker-compose volumes: https://docs.docker.com/compose/compose-file/#volumes
Reference of postgres docker image: https://hub.docker.com/_/postgres/
Reference of volumes and bind mounts: https://docs.docker.com/storage/bind-mounts/#choosing-the--v-or---mount-flag
You can save this container in a new image using docker container commit and use that newly created image in your docker-compose
docker container commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]
I however prefer creating images with the use of Dockerfiles and scripts to fill my data etc.