CentOS Stream 8
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Podman : Use Dockerfile
2021/03/22
 
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
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 ⇒ docker build -t [image name]:[tag] .

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

STEP 1: FROM centos
STEP 2: MAINTAINER ServerWorld <admin@srv.world>
--> ebbbd7990da
STEP 3: RUN dnf -y install nginx

.....
.....

STEP 6: CMD ["/usr/sbin/nginx", "-g", "daemon off;"]
STEP 7: COMMIT srv.world/centos-nginx:latest
--> 857fd2f5a02
857fd2f5a02678346c1d2da28f11b25c396679d0fafc621b6bb2800e9a7b5d48

[root@dlp ~]#
podman images

REPOSITORY                  TAG     IMAGE ID      CREATED             SIZE
srv.world/centos-nginx      latest  857fd2f5a026  About a minute ago  298 MB
srv.world/centos-httpd      latest  6a4b6e2cae37  17 minutes ago      322 MB
registry.centos.org/centos  latest  2f3766df23b6  3 months ago        217 MB

# run container

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

bb1f145aa93b8f65a8e88c04ddefe5a215876b03f365d40499cff28d7e620740

[root@dlp ~]#
podman ps

CONTAINER ID  IMAGE                   COMMAND               CREATED         STATUS             PORTS               NAMES
bb1f145aa93b  srv.world/centos-nginx  /usr/sbin/nginx -...  11 seconds ago  Up 11 seconds ago  0.0.0.0:80->80/tcp  nervous_shirley

# 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": "10.88.0.17",
                    "IPAddress": "10.88.0.17",
[root@dlp ~]#
curl 10.88.0.17

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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