Fedora 26
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Docker : Use Dockerfile
2017/07/30
 
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 17.92 kB
Step 1/10 : FROM fedora
 ---> 7f17e6b4a386
Step 2/10 : MAINTAINER ServerWorld <admin@srv.world>
 ---> Running in d67b7462d08d
 ---> 3d33461d5d8f
.....
.....
Removing intermediate container e73ed57dd718
Successfully built 40244c18250d

[root@dlp ~]#
docker images

REPOSITORY                          TAG     IMAGE ID         CREATED             SIZE
web_server                          latest  40244c18250d     11 seconds ago      461 MB
srv.world/fedora_httpd              latest  441834eaabe4     3 hours ago         478 MB
registry.fedoraproject.org/fedora   latest  7f17e6b4a386     4 weeks ago         232 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                                        
2dac0079a358 web_server "/usr/bin/su..  5 seconds  Up 4 sec  0.0.0.0:2022->22/tcp, 0.0.0.0:8081->80/tcp

# verify accesses

[root@dlp ~]#
curl localhost:8081

Hello DockerFile World
[root@dlp ~]#
ssh -p 2022 localhost

[root@2dac0079a358 ~]#
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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