Docker

Docker Image is basically a snapshot of file system at specific time can be used to create containers

1. Docker Installation:
   Install EPEL repositories to install docker
   yum install epel-release
   start docker service (service docker start)
   verify docker installed properly as below
   #docker version
   #docker info
   #ps faux

2. Creation of Docker Image:
   Create a script (Docker file) to create an image.
   We can get it from https://github.com/docker/docker/tree/master/contrib
   modify yum repo based on version we are trying to create docker image
   save the docker image using below command.
   docker save <id> > /tmp/centos65base.tar


  docker load < /root/centos65base.tar

3. Verification of image which we created
   #docker images
   #docker ps -all

[root@localhost ~]# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
<none>              <none>              ed49ce70a44d        21 minutes ago      272.4 MB

[root@localhost ~]# docker tag ed49ce70a44d centos7base:7

[root@localhost ~]# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
centos7base         7                   ed49ce70a44d        21 minutes ago      272.4 MB

4. Start the container from docker image as below. we can start from same machine or from other machine
#docker run -i -t ed49ce70a44d /bin/bash

In case if you exit from docker container
we need to below to get into container to re-connect.

docker start <container id>
docker attach <Container id>

do not exit from container, instead use  "ctrl +p and ctrl +q" to come to HOST system.

5. Commiting the changes that we made in container, when we commit new image gets created as below.
   [root@localhost ~]# docker commit 6d1b4d04bd5a centos7base-commit
   cea4e70c4bf833605ed06bb9fc60c722bf9870423633a93e5f0c030c7f7d4b8b

#docker images
REPOSITORY           TAG                 IMAGE ID            CREATED              VIRTUAL SIZE
centos7base-commit   latest              cea4e70c4bf8        About a minute ago   272.9 MB
centos7base          7                   ed49ce70a44d        54 minutes ago       272.4 MB



[root@HOST ~]# docker run --device=/dev/sdb --net='host' --privileged=true -it ed49ce70a44d /bin/bash

[root@container /]# fdisk -l

Disk /dev/sdb: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes




$ DOCKER_NVIDIA_DEVICES="--device /dev/nvidia0:/dev/nvidia0 --device /dev/nvidiactl:/dev/nvidiactl --device /dev/nvidia-uvm:/dev/nvidia-uvm"
$ sudo docker run -ti $DOCKER_NVIDIA_DEVICES tleyden5iwx/ubuntu-cuda /bin/bash


PRIVILIZED CONTAINER:
=====================
has access to all the devices, instead of being restricted to a small, sane set of devices;
retains all the capabilities of the host. It means that this container will be able to mknod, mount, etc.