CentOS Stream 9
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Podman : Use Dockerfile
2022/03/14
 
Use Dockerfile and create Container images automatically.
It is also useful for configuration management for Container images.
[1] For example, Create a Dockerfile that Nginx is installed and started.
[root@dlp ~]#
vi Dockerfile
# create new

FROM centos:stream9
MAINTAINER ServerWorld <admin@srv.world>

RUN dnf -y install nginx
RUN echo "Dockerfile Test on Nginx" > /usr/share/nginx/html/index.html

EXPOSE 80
CMD ["/usr/sbin/nginx", "-g", "daemon off;"]

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

[root@dlp ~]#
podman build -t srv.world/centos-nginx:latest .

STEP 1/6: FROM centos:stream9
STEP 2/6: MAINTAINER ServerWorld <admin@srv.world>
--> 10096b868a1
STEP 3/6: RUN dnf -y install nginx

.....
.....

STEP 5/6: EXPOSE 80
--> 6b26f04ed36
STEP 6/6: CMD ["/usr/sbin/nginx", "-g", "daemon off;"]
COMMIT srv.world/centos-nginx:latest
--> 762eb0a249a
Successfully tagged srv.world/centos-nginx:latest
762eb0a249a51c7e9fbc1c524207011bba773f7757e6140cdd4aa19eec8f83cf

[root@dlp ~]#
podman images

REPOSITORY              TAG         IMAGE ID      CREATED         SIZE
srv.world/centos-nginx  latest      762eb0a249a5  26 seconds ago  247 MB
srv.world/centos-httpd  latest      0c6c507d6e95  7 minutes ago   253 MB
quay.io/centos/centos   stream9     44ffcc4acee8  3 days ago      152 MB

# run container

[root@dlp ~]#
podman run -d -p 80:80 srv.world/centos-nginx

42707c810650c3b7f717226c3e827fdba913514341856993e746aaec698f3652

[root@dlp ~]#
podman ps

CONTAINER ID  IMAGE                          COMMAND               CREATED        STATUS            PORTS               NAMES
42707c810650  srv.world/centos-nginx:latest  /usr/sbin/nginx -...  7 seconds ago  Up 8 seconds ago  0.0.0.0:80->80/tcp  stoic_boyd

# verify accesses

[root@dlp ~]#
curl localhost

Dockerfile Test on Nginx
# also possible to access via container network

[root@dlp ~]#
podman inspect -l | grep \"IPAddress

               "IPAddress": "10.88.0.13",
                         "IPAddress": "10.88.0.13",

[root@dlp ~]#
curl 10.88.0.13

Dockerfile Test on Nginx
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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