A
D
ockerfile
is a
text
document
that contains a set of instructions.
The Docker image will be
built
from the set of
instructions
written
in the
dockerfile
.
Dockerhub
is the place where you will find many officials as well as
images
developed by developers/open source contributors.
But why a user needs to create a
Dockerfile
if there are already many images available?
The simplest
answer
is in most cases the user needs to create a
dockerfile
if existing images
do not fulfil
your current requirement.
The general syntax of
Dockerfile
follows the below pattern
# Comment
INSTRUCTION arguments
INSTRUCTION
represents a keyword in the dockerfile. Instructions perform specific tasks based on the order in which it appears in the
Dockerfile
.
Some of the most widely used
INSTRUCTIONS
are:
FROM COPY ADD ENV LABEL
Below is the sample dockerfile
FROM alpine MAINTAINER naiveskill ENTRYPOINT ["/bin/head"] CMD ["/etc/pam.d"]
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