I am using a machine with os ubuntu-18.05 in arm platform. It has some space issue and I want to work with docker images.
Usually, when I work on this machine I mount a directory and perform memory expensive operations there.
Is there any way I can pull image in host machine and make it work?
Example: I have mounted directory /home/test-mount, now instead of storing docker image and it's graph in location mentioned here Where are Docker images stored on the host machine? I want to efficiently pull, store and use image at path /home/test-mount, such that it can be easily switched to actual path.
Stop docker and make sure the following can be found in in /etc/docker/daemon.json:
{
"data-root": "/home/test-mount"
}
Now restart docker
Related
I am very new to docker so please pardon if anything stupid :P
I have docker running on my cloud server and was facing issue of running out of space because of docker overlay files. So I mounted 100GB of storage to the server at
/home/<user>/data
and in daemon.json configured the docker root directory to this newly mounted storage and copied all the old files but after that also when I check
df -h
overlay file shows size 36G. Am I doing something wrong
How can I increase this overlay to completely utilize the storage ?
PS: Also when it starts filling up it doesn't increase space it just fills up and all the apps stop working
Docker stores images, containers, and volumes under /var/lib/docker by default. If you haven't mounted another filesystem there, you are likely looking at the free space on your root filesystem.
When mounting another filesystem in this location, you likely want to move the current directory aside so you can copy it into the new filesystem. If you do restore the content, be sure to use a command that preserves ownership, permissions, and symlinks (I believe cp -a and tar both do this).
Also, make sure the docker engine is not running when you replace this directory, and be sure the filesystem type matches your current root filesystem type, or is compatible with your graph driver.
I had docker 18 when I pulled some docker images. Then I upgraded docker to docker 20, but it seems there are no images left (docker images) list nothing. Can I somehow retrieve them or I should pull them again?
A Docker container consists of network settings, volumes, and images. The location of Docker files depends on your operating system. Here is an overview for the most used operating systems:
Linux: /var/lib/docker/
Windows: C:\ProgramData\DockerDesktop
MacOS: ~/Library/Containers/com.docker.docker/Data/vms/0/
If you use the default storage driver in overlay2, Linux, then your Docker images are stored in /var/lib/docker/overlay2. There, you can find different files that represent read-only layers of a Docker image and a layer on top of it that contains your changes.
If the update overwrote the folder .... you'll have to pull again.
I'd like to keep some less used images on an external disk.
Is that possible?
Or should I move all images to an external disk changing some base path?
All of the Docker images are stored in an opaque, backend-specific format inside the /var/lib/docker directory. You can't move some of the images to a different location, only the entire Docker storage tree. See for example How to change the docker image installation directory?.
If you have images you only rarely use, you can docker rmi them for now and then docker pull them again from Docker Hub or another repository when you need them.
I am running windows 10 and the most recent version of docker. I am trying to run a docker image and transfer files to and from the image.
I have tried using the "docker cp" command, but from what I've seen online, this does not appear to work for docker images. It only works for containers.
When searching for info on this topic, I have only seen responses dealing with containers, not for images.
A docker image is basically a template used for containers. If you add something to the image it will show up in all of the containers. So if you just want to share a single set of files that don't change you can add the copy command to your docker file, and then run the new image and you'll find the container.
Another option is to use shared volumes. Shared volumes are basically folders that exist on both the host machine and the running docker container. If you move a file on the host system into that folder it will be available on the container (and if you put something from the container into the folder on the container side you can access it from the host side).
I was reading Project Atomic's guidance for images which states that the 2 main use cases for using a volume are:-
sharing data between containers
when writing large files to disk
I have neither of these use cases in my example using an Nginx image. I intended to mount a host directory as a volume in the path of the Nginx docroot in the container. This is so that I can push changes to a website's contents into the host rather then addressing the container. I feel it is easier to use this approach since I can - for example - just add my ssh key once to the host.
My question is, is this an appropriate use of a data volume and if not can anyone suggest an alternative approach to updating data inside a container?
One of the primary reasons for using Docker is to isolate your app from the server. This means you can run your container anywhere and get the same result. This is my main use case for it.
If you look at it from that point of view, having your container depend on files on the host machine for a deployed environment is counterproductive- running the same container on a different machine may result in different output.
If you do NOT care about that, and are just using docker to simplify the installation of nginx, then yes you can just use a volume from the host system.
Think about this though...
#Dockerfile
FROM nginx
ADD . /myfiles
#docker-compose.yml
web:
build: .
You could then use docker-machine to connect to your remote server and deploy a new version of your software with easy commands
docker-compose build
docker-compose up -d
even better, you could do
docker build -t me/myapp .
docker push me/myapp
and then deploy with
docker pull
docker run
There's a number of ways to achieve updating data in containers. Host volumes are a valid approach and probably the simplest way to achieve making your data available.
You can also copy files into and out of a container from the host. You may need to commit afterwards if you are stopping and removing the running web host container at all.
docker cp /src/www webserver:/www
You can copy files into a docker image build from your Dockerfile, which is the same process as above (copy and commit). Then restart the webserver container from the new image.
COPY /src/www /www
But I think the host volume is a good choice.
docker run -v /src/www:/www webserver command
Docker data containers are also an option for mounted volumes but they don't solve your immediate problem of copying data into your data container.
If you ever find yourself thinking "I need to ssh into this container", you are probably doing it wrong.
Not sure if I fully understand your request. But why you need do that to push files into Nginx container.
Manage volume in separate docker container, that's my suggestion and recommend by Docker.io
Data volumes
A data volume is a specially-designated directory within one or more containers that bypasses the Union File System. Data volumes provide several useful features for persistent or shared data:
Volumes are initialized when a container is created. If the container’s base image contains data at the specified mount point, that existing data is copied into the new volume upon volume initialization.
Data volumes can be shared and reused among containers.
Changes to a data volume are made directly.
Changes to a data volume will not be included when you update an image.
Data volumes persist even if the container itself is deleted.
refer: Manage data in containers
As said, one of the main reasons to use docker is to achieve always the same result. A best practice is to use a data only container.
With docker inspect <container_name> you can know the path of the volume on the host and update data manually, but this is not recommended;
or you can retrieve data from an external source, like a git repository