Docker : Use Dockerfile2020/12/14

	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 centos
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  11.78kB
Step 1/7 : FROM centos
 ---> 300e315adb2f
Step 2/7 : MAINTAINER ServerWorld <admin@srv.world>
 ---> Running in 56eed3200cd2
Removing intermediate container 56eed3200cd2
 ---> bcfcafa6508d
Step 3/7 : RUN dnf -y install httpd
 ---> Running in 4890062e6ec4
.....
.....
Successfully built fed1671fb260
Successfully tagged srv.world/centos-httpd:latest

[root@dlp ~]#

docker images

REPOSITORY               TAG       IMAGE ID       CREATED          SIZE
srv.world/centos-httpd   latest    fed1671fb260   21 seconds ago   250MB
srv.world/centos-nginx   latest    a51947547c71   17 minutes ago   285MB
centos                   latest    300e315adb2f   3 days ago       209MB

# run container

[root@dlp ~]#

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

d6012508a5ac2b9562e3905786cb7e70ed5a2fc2f3a925c5a22f4bd5413a7f0c

[root@dlp ~]#

docker ps

CONTAINER ID   IMAGE                    COMMAND                  CREATED         STATUS         PORTS                  NAMES
d6012508a5ac   srv.world/centos-httpd   "/usr/sbin/httpd -D …"   9 seconds ago   Up 8 seconds   0.0.0.0:8081->80/tcp   confident_sinoussi

# 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	iIt 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 remore 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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