The absolute path of your resources refers to an absolute path within the build context, not an absolute path on the host. So all the resources must be copied into the directory where you run the docker build and then provide the path of those resources within your Dockerfiles before building the image. (This refers to the location where you run your Dockerfile)

There is a closed [**issue**][1] for this as well. 


  [1]: https://github.com/moby/moby/issues/4592

You can&#39;t. You have to copy/hardlink the files/folders inside the directory where you build the docker image.

C# 7.2 introduces two new types: `Span&lt;T&gt;` and `Memory&lt;T&gt;` that have better performance over earlier C# types like `string[]`.

Question: What is the difference between `Span&lt;T&gt;` and `Memory&lt;T&gt;`? Why would I use one over the other?

What is the difference between Span&lt;T&gt; and Memory&lt;T&gt; in C# 7.2?

**How can I call SignalR Core Hub method from Controller?**  
I am using  ASP.NET Core 2.0 with Microsoft.AspNetCore.SignalR (1.0.0-alpha2-final).

I have windows service which communicate with Excel, SolidEdge ... When operation is complete it post request to my controller in ASP.NET Core application. Now I need to inform all clients connected to server with SignalR that external program completed some task.  
I can not change the way window service works. (Can not connect to SignalR from window service).  
I found plenty solution for old SignalR (`GlobalHost.ConnectionManager.GetHubContext`), but much has changed and those solutions are not working anymore.

My controller:

    [Route(&quot;API/vardesigncomm&quot;)]
    public class VarDesignCommController : Controller
    {
        [HttpPut(&quot;ProcessVarDesignCommResponse/{id}&quot;)]
        public async Task&lt;IActionResult&gt; ProcessVarDesignCommResponse(int id)
        {
            //call method TaskCompleted in Hub !!!! How?
     
            return new JsonResult(true);
        }
    }

My hub:

    public class VarDesignHub : Hub
    {
        public async Task TaskCompleted(int id)
        {
            await Clients.All.InvokeAsync(&quot;Completed&quot;, id);
        }
    }




Call SignalR Core Hub method from Controller

I have following line in my dockerfile

    COPY /root/url.net/volumes/persistent/url/root /usr/share/nginx/html

When I try to build the image with docker-compose I get

&gt; Service &#39;frontend&#39; failed to build: lstat
&gt; /root/url.net/volumes/persistent/url/root: no such file or
&gt; directory

I can cd from anywhere to `/root/url.net/volumes/persistent/url/root` with no problem on my machine.

How can I specify the absolute path of the folder in the dockerfile?




Docker COPY from ubuntu absolute path

I have following line in my dockerfile
<pre><code class="hljs language-bash">COPY /root/url.net/volumes/persistent/url/root /usr/share/nginx/html
</code></pre>
When I try to build the image with docker-compose I get
> Service 'frontend' failed to build: lstat
> /root/url.net/volumes/persistent/url/root: no such file or
> directory
I can cd from anywhere to <code>/root/url.net/volumes/persistent/url/root</code> with no problem on my machine.
How can I specify the absolute path of the folder in the dockerfile?

The [documentation](https://docs.docker.com/engine/userguide/eng-image/dockerfile_best-practices/) doesn&#39;t elaborate on the topic a lot. It says:


&gt;  Minimize the number of layers 
&gt;
&gt; Prior to Docker 17.05, and even more, prior to
&gt; Docker 1.10, it was important to minimize the number of layers in your
&gt; image. The following improvements have mitigated this need:
&gt; 
&gt; In Docker 1.10 and higher, only RUN, COPY, and ADD instructions create
&gt; layers. Other instructions create temporary intermediate images, and
&gt; no longer directly increase the size of the build.
&gt; 
&gt; Docker 17.05 and higher add support for multi-stage builds, which
&gt; allow you to copy only the artifacts you need into the final image.
&gt; This allows you to include tools and debug information in your
&gt; intermediate build stages without increasing the size of the final
&gt; image.

It looks like the latest Docker versions don&#39;t solve the problem of handling many layers. They rather strive to reduce their number in the final image. Most importantly, the docs don&#39;t tell **why** many layers are bad.

I&#39;m aware of the [AUFS limit](https://stackoverflow.com/a/39383801/2116625) of 42 layers. It makes sense to keep the number of layers small for widely used images because it helps other images built on top of them fit the restriction. However, there are another storage drivers and images for other purposes.

It is also good to keep images small for an obvious reason - they take up disk space and network bandwidth. However, I don&#39;t think that [chaining RUN statements](https://stackoverflow.com/questions/39223249/multiple-run-vs-single-chained-run-in-dockerfile-what-is-better) and thus squashing many layers into one helps in general. In case different RUNs update different parts of the filesystem one layer and many layers together should be approximately the same in size.

On the other hand, many layers allow to make use of cache and rebuild images faster. They are also pulled in parallel.

I work in a small team with a private Docker registry. We won&#39;t ever meet the 42 layers restriction and care mostly about performance and development speed. 

If so, should I minimize the number of docker layers?


Should I minimize the number of docker layers?

I am using `Docker version 17.09.0-ce`, and I see that containers are marked as unhealthy. Is there an option to get the container restart instead of keeping the container as unhealthy?

Restarting an unhealthy docker container based on healthcheck

[asp.net core 2.0 and docker for linux]

I am completely new to docker and trying to figure out how to use docker in a case where i have a solution with 2 projects. All tutorials i&#39;ve seen show with single project.

So, if someone could show step by step solution i would really appreciate it.

i have a solution structure like:

    Solution.sln
    |______WebAPIProject.csproj
    |______ClassLibraryProject.csproj

In Visual studio, i&#39;ve added docker support to solution and got these files:

Under WebAPIProject, it created this **Docker file**:

    FROM microsoft/aspnetcore:2.0
    ARG source
    WORKDIR /app
    EXPOSE 80
    COPY ${source:-obj/Docker/publish} .
    ENTRYPOINT [&quot;dotnet&quot;, &quot;WebAPIProject.dll&quot;]

then, under separate docker-compose &#39;project&#39; i&#39;ve got:

**docker-compose.ci.build.yml**

    version: &#39;3&#39;
    
    services:
      ci-build:
        image: microsoft/aspnetcore-build:1.0-2.0
        volumes:
          - .:/src
        working_dir: /src
        command: /bin/bash -c &quot;dotnet restore ./Solution.sln &amp;&amp; dotnet publish ./Solution.sln -c Release -o ./obj/Docker/publish&quot;

and **docker.compose.yml** file

    version: &#39;3&#39;
    
    services:
      WebAPIProject:
        image: WebAPIProject
        build:
          context: ./WebAPIProject
          dockerfile: Dockerfile

I am sure its something trivial with paths but i am just pretty lost with it all so if someone could shed a bit of a light on it?

asp.net core 2.0 - multiple projects solution docker file

I want to know why we have two different options to do the same thing, What are the differences between the two.

What Is The Difference Between Binding Mounts And Volumes While Handling Persistent Data In Docker Containers?

How are [Packer](https://packer.io) and [Docker](https://docker.com) different? Which one is easier/quickest to provision/maintain and why? What is the pros and cons of having a `dockerfile`?

How are Packer and Docker different? Which one should I prefer when provisioning images?

`docker-compose run` has a flag `--rm` that auto removes the container after run. I am wondering if theres an equivalent config with docker-compose.yml for a specific service, as one of which services i got in yml is a one off build process which should just output the compile file and disappear itself. 

Auto remove container with docker-compose.yml

**Issue**: Can not stop docker containers, whenever I try to stop containers I get the following Error message,

    ERROR: for yattyadocker_web_1  cannot stop container: 1f04148910c5bac38983e6beb3f6da4c8be3f46ceeccdc8d7de0da9d2d76edd8: Cannot kill container 1f04148910c5bac38983e6beb3f6da4c8be3f46ceeccdc8d7de0da9d2d76edd8: rpc error: code = PermissionDenied desc = permission denied

**OS Version/build:** Ubuntu 16.04 | Docker Version 17.09.0-ce, build afdb6d4 | Docker Compose version 1.17.1, build 6d101fb

**Steps to reproduce:**

- Created a rails project with Dockerfile and docker-compose.yml. docker-compose.yml is of version 3.
- Image is built successfully with either `docker build -t &lt;project name&gt; . ` or `docker-compose up --build`
- Containers boots up and runs successfully.
- Try to stop docker compose with docker-compose down.

**What I tried:**: 

- I have to run `sudo service docker restart` and then the containers can be removed.
- Uninstalled docker, removed docker directory and then re installed everything. Still facing same issue. 

**Note**: This configuration was working correctly earlier, but somehow file permissions might have changed and I am seeing this error. I have to run `sudo service docker restart` and then the containers can be removed. But this is highly inconvenient and I don&#39;t know how to troubleshoot this.


**Reference Files:**

    # docker-compose.yml
    version: &#39;3&#39;
    volumes:
      db-data:
        driver: local
      redis-data:
        driver: local  
    services:
      db:
        image: postgres:9.4.1
        volumes:
          - db-data:/var/lib/postgresql/data
        ports:
          - &quot;5432:5432&quot;
        env_file: local_envs.env
      web:
        image: yattya_docker:latest
        command: bundle exec puma -C config/puma.rb
        tty: true
        stdin_open: true
        ports:
          - &quot;3000:3000&quot;
        links:
          - db
          - redis
          - memcached
        depends_on:
          - db
          - redis
          - memcached
        env_file: local_envs.env
      redis:
        image: redis:3.2.4-alpine
        ports:
          # We&#39;ll bind our host&#39;s port 6379 to redis&#39;s port 6379, so we can use
          # Redis Desktop Manager (or other tools) with it:
          - 6379:6379
        volumes:
          # We&#39;ll mount the &#39;redis-data&#39; volume into the location redis stores it&#39;s data:
          - redis-data:/var/lib/redis
        command: redis-server --appendonly yes
      memcached:
        image: memcached:1.5-alpine
        ports:
          - &quot;11211:11211&quot;
      clock:
        image: yattya_docker:latest
        command: bundle exec clockwork lib/clock.rb
        links:
          - db
        depends_on:
          - db
        env_file: local_envs.env
      worker:
        image: yattya_docker:latest
        command: bundle exec rake jobs:work
        links: 
          - db
        depends_on: 
          - db
        env_file: local_envs.env

And Dockerfile:

    # Dockerfile
    FROM ruby:2.4.1
    
    RUN apt-get update &amp;&amp; apt-get install -y nodejs --no-install-recommends &amp;&amp; rm -rf /var/lib/apt/lists/*
    
    ENV APP_HOME /app
    RUN mkdir -p $APP_HOME
    WORKDIR $APP_HOME
    
    ADD Gemfile* $APP_HOME/
    RUN bundle install
    
    ADD . $APP_HOME
    
    RUN mkdir -p ${APP_HOME}/log
    RUN cat /dev/null &gt; &quot;$APP_HOME/log/development.log&quot;
    
    RUN mkdir -p ${APP_HOME}/tmp/cache \
        &amp;&amp; mkdir -p ${APP_HOME}/tmp/pids \
        &amp;&amp; mkdir -p ${APP_HOME}/tmp/sockets
    
    EXPOSE 3000



Docker Containers can not be stopped or removed - permission denied Error

While diving into Docker, Google Cloud and Kubernetes, and without clearly understanding all three of them yet, it seems to me these products are overlapping, yet they&#39;re not compatible.

For example, a `docker-compose.yml` file needs to be re-written so an app can be deployed to Kubernetes.

Could someone provide a high-level, rough description of where Docker, Docker Compose, Docker Cloud, and Kubernetes overlap and where one is dependent on the other?


What&#39;s the difference between Docker Compose and Kubernetes?

I am currently trying out this tutorial for `node express` with `mongodb`
https://medium.com/@sunnykay/docker-development-workflow-node-express-mongo-4bb3b1f7eb1e

the first part works fine where to build the `docker-compose.yml`
it works totally fine building it locally so I tried to tag it and push into my `dockerhub` to learn and try more.

this is originally what&#39;s in the `yml` file followed by the tutorial

    version: &quot;2&quot;
    services:
      web:
        build: .
        volumes:
          - ./:/app
        ports:
          - &quot;3000:3000&quot;

this works like a charm when I use `docker-compose build` and `docker-compose up`

so I tried to push it to my dockerhub and I also tag it as `node-test`

I then changed the `yml` file into

    version: &quot;2&quot;
    services:
      web:
        image: &quot;et4891/node-test&quot;
        volumes:
          - ./:/app
        ports:
          - &quot;3000:3000&quot;

then I removed all images I have previously to make sure this also works...but when I run `docker-compose build`  I see this message `error: web uses an image, skipping` and nothing happens.

I tried googling the error but nothing much I can find.

Can someone please give me a hand?

Thanks in advance

Docker: Uses an image, skipping (docker-compose)

I have a service that I am bringing up through Rancher via docker-compose. The issue I am running into is that I need to set a password after the container has been deployed.

The way rancher secrets work, is that I set my secret in and rancher will mount a volume on my container with a file containing my secret. I was hoping to be able to execute a script to grab that secret, and set it as a password on my config file.

I don&#39;t believe I have a way to get that secret in through the Dockerfile as I don&#39;t want the secret to be in git, so I&#39;m left looking at doing it via docker-compose.

Does anyone know if this is possible?

docker-compose, run a script after container has started?

How do I write Dockerfile commands to install the following in alpine docker image:

 1. software-properties-common
 2. openjdk-8-jdk
 3.  python3
 4. nltk 
 5. Flask



Install packages in Alpine docker

I was doing some complex stuff with docker, but as turn out I don&#39;t know what `-it` flag means.
Recently I&#39;ve come across on some example of `docker run` command which has confused me a little. 

    docker run -itd ubuntu:xenial /bin/bash 

My question is what is sense to write `-it` flag here, if container during instantiation run `bin/bash`

In documentation we have an example

    docker run --name test -it debian

with explanation 

&gt; The -it instructs Docker to allocate a pseudo-TTY connected to the
&gt; container’s stdin; creating an interactive bash shell in the
&gt; container.

and explanation for -t flag from help page

&gt;   -t, --tty                     Allocate a pseudo-TTY

if I delete -it flag during 

    docker run -d ubuntu:xenial /bin/bash

my newly created container doesn&#39;t live so much

in `docker ps -a` 

it is designated as exited

Sorry, if my question quite stupid, I can&#39;t find explanation on the Internet (I have significant misunderstanding of that point).




Content Type	Original Author	Original Content on Stackoverflow
Question	isADon	View Question on Stackoverflow
Solution 1 - Docker	Ravindu Nirmal Fernando	View Answer on Stackoverflow
Solution 2 - Docker	Stefano	View Answer on Stackoverflow

Docker COPY from ubuntu absolute path

Docker Problem Overview

Docker Solutions

Solution 1 - Docker

Solution 2 - Docker

Call SignalR Core Hub method from Controller

What is the difference between Span<T> and Memory<T> in C# 7.2?

Attributions