Fedora 27
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Docker : Use Dockerfile
2017/12/21
 
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
 ---> 422dc563ca32
Step 2/10 : MAINTAINER ServerWorld <admin@srv.world>
 ---> Running in 100120441df0
 ---> 7b4c1c1e90a9
.....
.....
Removing intermediate container ecbaf116453d
Successfully built 95184ed89cc4

[root@dlp ~]#
docker images

REPOSITORY               TAG         IMAGE ID            CREATED             SIZE
web_server               latest      95184ed89cc4        12 seconds ago      473 MB
srv.world/fedora_httpd   latest      32918df26202        9 minutes ago       564 MB
docker.io/fedora         latest      422dc563ca32        5 weeks ago         252 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                                 ...
bbff4c5ce065  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@bbff4c5ce065 ~]#
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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