Create Lab#7:RUN_instruction.md

Author: sangam14

beginners/dockerfile/Lab#7:RUN_instruction.md

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+# Lab #7: RUN instruction
+
+The `RUN` instruction execute command on top of the below layer and create a new layer. <br>
+RUN instruction can be wrote in two forms:
+- RUN <command> (shell form)
+- RUN ["executable", "param1", "param2"] (exec form)
+
+## Pre-requisite:
+
+## Tested Infrastructure
+
+<table class="tg">
+  <tr>
+    <th class="tg-yw4l"><b>Platform</b></th>
+    <th class="tg-yw4l"><b>Number of Instance</b></th>
+    <th class="tg-yw4l"><b>Reading Time</b></th>
+    
+  </tr>
+  <tr>
+    <td class="tg-yw4l"><b> Play with Docker</b></td>
+    <td class="tg-yw4l"><b>1</b></td>
+    <td class="tg-yw4l"><b>5 min</b></td>
+    
+  </tr>
+  
+</table>
+
+## Pre-requisite
+
+- Create an account with [DockerHub](https://hub.docker.com)
+- Open [PWD](https://labs.play-with-docker.com/) Platform on your browser 
+- Click on **Add New Instance** on the left side of the screen to bring up Alpine OS instance on the right side
+
+## Assignment:
+
+- Create an image with RUN instruction
+- Combining multiple RUN instruction to one
+
+### Create an image with RUN instruction
+```
+FROM alpine:3.9.3
+LABEL maintainer="Collabnix"
+RUN apk add --update 
+RUN apk add curl
+RUN rm -rf /var/cache/apk/
+```
+#### Building Docker image
+```
+$ docker image build -t run:v1 .
+```
+#### Checking layer of the image
+```
+$  docker image history run:v1 
+IMAGE               CREATED             CREATED BY                                      SIZE                
+NT
+5b09d7ba1736        19 seconds ago      /bin/sh -c rm -rf /var/cache/apk/               0B                  
+192115cc597a        21 seconds ago      /bin/sh -c apk add curl                         1.55MB              
+0518580850f1        43 seconds ago      /bin/sh -c apk add --update                     1.33MB              
+8590497d994e        45 seconds ago      /bin/sh -c #(nop)  LABEL maintainer=Collabnix   0B                  
+cdf98d1859c1        4 months ago        /bin/sh -c #(nop)  CMD ["/bin/sh"]              0B                  
+<missing>           4 months ago        /bin/sh -c #(nop) ADD file:2e3a37883f56a4a27…   5.53MB 
+```
+Number of layers 6
+
+#### Checking image size
+```
+$ docker image ls run:v1
+REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
+run                 v1                  5b09d7ba1736        4 minutes ago       8.42MB
+```
+Its 8.42MB
+
+### Combining multiple RUN instruction to one
+```
+FROM alpine:3.9.3
+LABEL maintainer="Collabnix"
+RUN apk add --update \ &&
+	apk add curl \ &&  
+	rm -rf /var/cache/apk/
+```
+#### Building Docker image
+```
+$ docker image build -t run:v2 .
+```
+#### Checking layer of the image
+```
+$ docker image history run:v2
+IMAGE               CREATED             CREATED BY                                      SIZE            
+NT
+784298155541        50 seconds ago      /bin/sh -c apk add --update  && apk add curl…   1.55MB              
+8590497d994e        8 minutes ago       /bin/sh -c #(nop)  LABEL maintainer=Collabnix   0B                  
+cdf98d1859c1        4 months ago        /bin/sh -c #(nop)  CMD ["/bin/sh"]              0B                  
+<missing>           4 months ago        /bin/sh -c #(nop) ADD file:2e3a37883f56a4a27…   5.53MB
+```
+Number of layers 4
+#### Checking image size
+```
+$ docker image ls run:v2
+REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
+run                 v2                  784298155541        3 minutes ago       7.08MB
+```
+its now 7.08MB 
+
+## Contributor
+[Savio Mathew](https://www.linkedin.com/in/saviovettoor)
+
+Next » [Lab #8: ARG instruction](https://dockerlabs.collabnix.com/beginners/dockerfile/arg.html)