Docker Cheat Sheet

Docker
==========================================
Process ID 1 of any container is very critical. If we stop that process, container will stop

1. To search docker image in repository
# docker search container-name

2. To check downloaded images
# docker images

3. To check running docker containers
# docker ps

4. To check all docker containers on system
# docker ps -a

5. To check container configuration like IP, gateway etc.
# docker inspect docker-name

6. To run a container
# docker run -it --name fedora-web -d fedora /bin/bash
# docker run -it --net my_network ubuntu:14.04
# docker run -it -p 8080:80 --name apache2-web apache2:1.1   
docker run -it --name ubutnu-mem -m 500M -d ubuntu /bin/bash
-d -- to run container in backgroud
-p -- to map host ports with container port
-i -- Keep STDIN open even if not attached
-m -- to set memory limit

7. To build image using running container
# docker commit -m "ubuntu-db image" ubuntu-db umeshso/ubuntu-db:1.0

8. To create our own network
# docker network create my_network
# docker network ls

9. To remove container
# docker rm container-ID/container-name

10. To remove container image
# docker rmi container-ID

11. To build docker from Dockerfile
# docker build -t apache2:1.1 .        --- -t is used to tag the image

12. To execute command in docker
# docker exec -it ubuntu-db mysqladmin status
#  docker exec -it ubuntu-web service apache2 status

13. To login into container
# docker attach ubuntu-db

14. To start and stop container
# docker start container-name/ID
# docker stop container-name/ID

15. To download and upload image from repo
# docker pull image-name
# docker push image-name

16. To check stats
# docker stats --all

CONTAINER           CPU %               MEM USAGE / LIMIT      MEM %               NET I/O             BLOCK I/O           PIDS
6c5485af8267        0.03%               336 MiB / 1.953 GiB    16.80%              1.11 MB / 1.97 MB   383 MB / 144 MB     34
c05ba59feed4        0.00%               78.1 MiB / 1.953 GiB   3.90%               96.1 MB / 12.7 MB   147 MB / 204 MB     12

17. To monitor container
# docker logs container-ID
# docker top container-ID

18. To check docker info
# docker info

19. Enable swappiness 
# add below line /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="cgroup_enable=memory swapaccount=1"
# update-grub

20. To update resources
docker update --cpuset-cpus "1" --memory "1g" docker-id

21. Build parameters
FROM: - Base image to be used 
RUN: - allows you to install your application and packages required for it.
CMD: - the command the container executes by default when you launch the built image. Dockerfile have only one CMD.
COPY: - copy files from main host to container
WORKDIR: - Set the current working directory
EXPOSE: - Ports to open 
ENV: - to update the PATH environment variable for the software your container installs
USER - to add user and group into container
ENTRYPOINT: - should be defined when using the container as an executable.
CMD is the default argument to container. Without entrypoint, default argument is command that is executed. With entrypoint, cmd is passed to entrypoint as argument.
The ENTRYPOINT specifies a command that will always be executed when the container starts. The CMD specifies arguments that will be fed to the ENTRYPOINT.

Example: -----------------------------------------------------------------------------------------------------------------
FROM ubuntu
MAINTAINER umesh.bhatia@ucsf.edu
EXPOSE 80 443
RUN mkdir /data
WORKDIR /data
RUN apt-get update && apt-get install -y apache2
RUN service apache2 start
COPY 000-default.conf /etc/apache2/sites-enabled/000-default.conf
CMD [ "/bin/bash" ]

22. Swarm
To initialize: - 
# docker swarm init --advertise-addr 192.168.56.101
To check swarm configuration: - 
# docker info
To join worker in cluster: -
# docker swarm join-token worker
To join manager in cluster: - 
# docker swarm join-token manager
To create service in cluster: - 
# docker service create -p 8080:80 --name webserver nginx
To create replicas for services: - 
# docker service create --name replicated_service --replicas 3 nginx
To create service globally on all nodes: - 
# docker service create --name global_service --mode global nginx
To list services running on cluster: -
# docker service ls
To check nodes for services: - 
# docker service ps global_service
To increase replicas: - 
# docker service scale replicated_service=5
To check info of services running on cluster: - 
# docker service inspect --pretty replicated_service
To remove services: -
# docker service rm webserver