Docker : Use Dockerfile2018/05/30

	Use Dockerfile and create Docker images automatically. It is also useful for configuration management.
[1]	For example, Create a Dockerfile to install httpd and sshd and also install Supervisor to control multiple services on a Container.

[root@dlp ~]#

vi Dockerfile

# create new

FROM fedora
MAINTAINER ServerWorld <admin@srv.world>

RUN dnf -y install openssh-server httpd supervisor
RUN echo "Hello DockerFile World" > /var/www/html/index.html
RUN mkdir /root/.ssh; chown root. /root/.ssh; chmod 700 /root/.ssh
RUN ssh-keygen -A

ADD supervisord.conf /etc/supervisord.conf
ADD .ssh/id_rsa.pub /root/.ssh/authorized_keys

EXPOSE 22 80
CMD ["/usr/bin/supervisord"]

# create a Supervisor template

[root@dlp ~]#

vi supervisord.conf

[supervisord]
nodaemon=true

[program:sshd]
command=/usr/sbin/sshd -D
autostart=true
autorestart=true

[program:httpd]
command=/usr/sbin/httpd -D FOREGROUND
autostart=true
autorestart=true

# generate SSH key

[root@dlp ~]#

ssh-keygen -q -N "" -f /root/.ssh/id_rsa

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

[root@dlp ~]#

docker build -t web_server:latest .

Sending build context to Docker daemon 15.87 kB
Step 1/10 : FROM fedora
 ---> cc510acfcd70
Step 2/10 : MAINTAINER ServerWorld <admin@srv.world>
 ---> Running in 459517c445ff
 ---> 003b97476927
.....
.....
Removing intermediate container b99015ea2982
Successfully built e0fe7c3805c4

[root@dlp ~]#

docker images

REPOSITORY               TAG                 IMAGE ID            CREATED             SIZE
web_server               latest              e0fe7c3805c4        2 minutes ago       482 MB
srv.world/fedora_httpd   latest              f153182d83f9        9 minutes ago       525 MB
docker.io/fedora         latest              cc510acfcd70        3 weeks ago         253 MB

# run Container on background

[root@dlp ~]#

docker run -d -p 2022:22 -p 8081:80 web_server

[root@dlp ~]#

docker ps

CONTAINER ID  IMAGE      COMMAND       CREATED      STATUS       PORTS                                 ...
4419142668a9  web_server "/usr/bin...  14 secon...  Up 11 se...  0.0.0.0:2022->22/tcp, 0.0.0.0:8081->80...

# verify accesses

[root@dlp ~]#

curl localhost:8081

Hello DockerFile World
[root@dlp ~]#

ssh -p 2022 localhost

[root@4419142668a9 ~]#

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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