title: I can't find the file I copied with the COPY command in dockerfile
body: <p>I'm learning Docker. I created a dockerfile like this.</p>
  
  <pre><code>FROM alpine:3.10.3
  
  WORKDIR /dev/mirai
  COPY mirai-console-wrapper-0.3.0.jar .
  
  </code></pre>
  
  <p>Then i build it with command</p>
  
  <pre><code>docker build -t mirai:0.0.1 .
  </code></pre>
  
  <p>It seems like I successfully built it.</p>
  
  <pre><code>Sending build context to Docker daemon  10.04MB
  Step 1/3 : FROM alpine:3.10.3
   ---&gt; 965ea09ff2eb
  Step 2/3 : WORKDIR /dev/mirai
   ---&gt; Using cache
   ---&gt; d3af4049af4a
  
  Step 3/3 : COPY mirai-console-wrapper-0.3.0.jar .
   ---&gt; Using cache
   ---&gt; 56df1145ecab
  Successfully built 56df1145ecab
  Successfully tagged mirai:0.0.1
  SECURITY WARNING: You are building a Docker image from Windows against a non-Windows Docker host. All files and directories added to build context will have
   '-rwxr-xr-x' permissions. It is recommended to double check and reset permissions for sensitive files and directories.
  </code></pre>
  
  <p>But when i run this image</p>
  
  <pre><code>docker run -it mirai:0.0.1
  </code></pre>
  
  <p>I can't find my copied file mirai-console-wrapper-0.3.0.jar</p>
  
  <pre><code>/dev/mirai # ls
  /dev/mirai #
  </code></pre>
  
  <p>There is nothing in the folder mirai.
  I just want to copy the file in my docker image.</p>