DevOps Classroom notes 26/May/2026

USER

• In linux machines, root user has full permissions,
• By default when you build image the user is going to root.
• Example

FROM alpine:3
CMD ["sleep", "1d"]

• docker exec command can run a command in a running container

docker exec test whoami
docker exec -it test1 /bin/sh

• It is recommended to run you application as a normal user
• As part of your docker image building create a user and switch to that user
• Dockerfile

FROM alpine:3
RUN adduser -D -h /app appuser
USER appuser
CMD ["sleep", "1d"]

WORKDIR

• WORKDIR instruction make a particular folder your current working directory

FROM alpine:3
RUN adduser -D -h /app appuser
USER appuser
WORKDIR /app
CMD ["sleep", "1d"]

Running docker contianers

• Playing with docker commands
• Figure out aliases dont memorize

docker images
docker image ls
docker ps
docker container ls

• A container can be run in two modes
  • attached:
    • This is default
  • background (detached)
• To run a docker command all we need to do is

docker run <image>

• Detached mode

docker run -d <image>

• When we create a container, each container gets a
  • unique id
  • unique name (if the name is not provided, docker generates a name)
• To provide name

docker run -d --name <name> <image>

• Name conflicts apply, two containers having same name
• A container might have an application which is running on some port, we use portforwording for that

docker run -d  -p 18000:80 --name <name> <image>

• To ensure we have dynamic portforwarding (When we have EXPOSE instruction)

docker run -d  -P --name <name> <image>