Ubuntu 18.04
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Docker : Use Dockerfile
2018/06/12
 
Use Dockerfile and create Docker images automatically.
It is also useful for configuration management.
[1] For example, Create a Dockerfile to install apache2 and sshd and also install Supervisor to control multiple services on a Container.
root@dlp:~#
vi Dockerfile
# create new

FROM ubuntu
MAINTAINER ServerWorld <admin@srv.world>

RUN apt-get update
RUN apt-get -y install openssh-server apache2 supervisor
RUN echo "Hello DockerFile World" > /var/www/html/index.html
RUN mkdir /var/run/sshd; chmod 755 /var/run/sshd
RUN mkdir /root/.ssh; chown root. /root/.ssh; chmod 700 /root/.ssh
RUN ssh-keygen -A

ADD supervisord.conf /etc/supervisor/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:apache2]
command=/usr/sbin/apachectl -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  30.72kB
Step 1/12 : FROM ubuntu
 ---> 113a43faa138
Step 2/12 : MAINTAINER ServerWorld <admin@srv.world>
 ---> Running in 0f01060ab8b6
Removing intermediate container 0f01060ab8b6
 ---> 6fdcd1fb1603
Step 3/12 : RUN apt-get update
 ---> Running in 25a345502a0d
.....
.....
Successfully built 46fdaf40a0fe
Successfully tagged web_server:latest

root@dlp:~#
docker images

REPOSITORY                 TAG                 IMAGE ID            CREATED             SIZE
web_server                 latest              46fdaf40a0fe        11 seconds ago      313MB
srv.world/ubuntu_apache2   latest              b2d00f9d9fb4        About an hour ago   218MB
ubuntu                     latest              113a43faa138        6 days ago          81.2MB

# run Container on background

root@dlp:~#
docker run -d -p 2022:22 -p 8081:80 web_server

16931dff49924273f06405958010120ea0e7aaf289acf9c1fc54704944c16290
root@dlp:~#
docker ps

CONTAINER ID  IMAGE       COMMAND                 CREATED        STATUS         PORTS                                        NAMES
16931dff4992  web_server  "/usr/bin/supervisord"  9 seconds ago  Up 8 seconds   0.0.0.0:2022->22/tcp, 0.0.0.0:8081->80/tcp   xenodochial_stonebraker

# verify accesses

root@dlp:~#
curl localhost:8081

Hello DockerFile World
root@dlp:~#
ssh -p 2022 localhost /bin/hostname

The authenticity of host '[localhost]:2022 ([::1]:2022)' can't be established.
ECDSA key fingerprint is SHA256:OgVxqKSJ1EtcnbQllocvs5dc++CPDzrBvpfh9AK1hds.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[localhost]:2022' (ECDSA) to the list of known hosts.
16931dff4992
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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