Lab #7: Create an image with RUN instruction

The RUN instruction execute command on top of the below layer and create a new layer.
RUN instruction can be wrote in two forms:

  • RUN (shell form)
  • RUN [“executable”, “param1”, “param2”] (exec form)

Pre-requisite:

Tested Infrastructure

Platform Number of Instance Reading Time
Play with Docker 1 5 min

Pre-requisite

  • Create an account with DockerHub
  • Open PWD 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

Next » Create an image with ARG instruction