Docker : Use Dockerfile2022/07/29

	Use Dockerfile and create Docker images automatically. It is also useful for configuration management.
[1]	For example, Create a Dockerfile that Apache httpd is installed and started.

[root@dlp ~]#

vi Dockerfile

# create new

FROM quay.io/centos/centos:stream9
MAINTAINER ServerWorld <admin@srv.world>

RUN dnf -y install httpd
RUN echo "Dockerfile Test on Aapche httpd" > /var/www/html/index.html

EXPOSE 80
CMD ["-D", "FOREGROUND"]
ENTRYPOINT ["/usr/sbin/httpd"]

# build image ⇒ docker build -t [image name]:[tag] .

[root@dlp ~]#

docker build -t srv.world/centos-httpd:latest ./

Sending build context to Docker daemon   21.5kB
Step 1/7 : FROM quay.io/centos/centos:stream9
 ---> 61674c24ebbf
Step 2/7 : MAINTAINER ServerWorld <admin@srv.world>
 ---> Running in e126c7956669
Removing intermediate container e126c7956669
 ---> 441ed9ada006
Step 3/7 : RUN dnf -y install httpd
 ---> Running in 68d9a9ea50fb
 
.....
.....

Successfully built db5fee1dd895
Successfully tagged srv.world/centos-httpd:latest

[root@dlp ~]#

docker images

REPOSITORY               TAG       IMAGE ID       CREATED              SIZE
srv.world/centos-httpd   latest    db5fee1dd895   About a minute ago   257MB
srv.world/centos-nginx   latest    7fd90c511873   7 minutes ago        251MB
quay.io/centos/centos    stream9   61674c24ebbf   30 hours ago         152MB

# run container

[root@dlp ~]#

docker run -d -p 8081:80 srv.world/centos-httpd

40b410e2dd655ff89b25842c613133c38729fe4be6d3b3066ed765b2b3d16b88

[root@dlp ~]#

docker ps

CONTAINER ID   IMAGE                    COMMAND                  CREATED          STATUS          PORTS                                   NAMES
40b410e2dd65   srv.world/centos-httpd   "/usr/sbin/httpd -D …"   16 seconds ago   Up 16 seconds   0.0.0.0:8081->80/tcp, :::8081->80/tcp   dreamy_morse

# verify accesses

[root@dlp ~]#

curl localhost:8081

Dockerfile Test on Aapche httpd

The format of Dockerfile is [INSTRUCTION arguments] .
Refer to the following description for INSTRUCTION.

INSTRUCTION	Description
FROM	It sets the Base Image for subsequent instructions.
MAINTAINER	It sets the Author field of the generated images.
RUN	It will execute any commands when Docker image will be created.
CMD	It will execute any commands when Docker container will be executed.
ENTRYPOINT	It will execute any commands when Docker container will be executed.
LABEL	It adds metadata to an image.
EXPOSE	It informs Docker that the container will listen on the specified network ports at runtime.
ENV	It sets the environment variable.
ADD	It copies new files, directories or remote file URLs.
COPY	It copies new files or directories. The differences of [ADD] are that it's impossible to specify remote URL and also it will not extract archive files automatically.
VOLUME	It creates a mount point with the specified name and marks it as holding externally mounted volumes from native host or other containers.
USER	It sets the user name or UID.
WORKDIR	It sets the working directory.

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