Lab #7: 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

Contributor

Savio Mathew

Next » Lab #8: ARG instruction