What is docker?
Docker is an environment with its own OS+ user space (related packages & modules) that resides on a bare-metal system and uses system HW/Kernel resources to serve a different purpose.
We must understand 3 environments (Bare metal, Docker, virtualization)
·
Bare
metal is one kind of environment where we test our GPUs directly
·
Docker
is one kind of environment that is separated from Bare metal.
Virtualization is software, that makes computing environments independent of physical infrastructure. In contrast, cloud computing is a service that delivers shared computing resources (software and/or data) on demand via the Internet.
· If you launch Docker, it has its own user space with all dependent packages and its own OS.
The beauty of the docker concept :
Docker is platform-independent and can run on any machine regardless of the operating system present.
Docker
is controlled by a kernel space.
·
Kernel
sitting very close to the hardware.
·
If
Kernel space/Firmware is broken/crashed, we can’t do anything.
· Both Bare-metal and Docker have the packages, Except Docker does not have kernel space. Docker will use kernel space which is available on the bare metal.
Docker architecture components & How does docker work?
Docker architecture comprises 3 main components
1. Docker Client: This is the interface through which users interact. It communicates with the docker daemon.
2. Docker Host: Here, Docker daemon listens for docker API requests and manages various docker objects, including images, containers, networks, and volumes
3. Docker Registry: This is where Docker images are stored. Docker hub, for instance, is a widely used public registry
For operations related to Docker on your machines or servers, such as Docker building, pulling, or running containers, the Docker daemon must be active & running.
Note: Based on OS, you can install & activate the Docker daemon by using the steps below
Ubuntu 18.04/20.04/22.04/24.04
sudo apt-get -y install apt-transport-https ca-certificates curl
curl -fsSL https://get.docker.com/ | sh
sudo systemctl start docker → start the Docker daemon:
sudo systemctl status docker → verify it's running or not [ Active: active (running)]
sudo systemctl enable docker → make sure it starts at every server reboot
Docker & container related commands
sudo docker pull <docker_name_based_on_OS> cmd will pull the specific Docker image into the machine
sudo docker images ==> cmd will list the available dockers in the present machine
sudo docker rmi -f docker_id ==> cmd will delete a single specific docker in the present machine
sudo docker rmi -f docker_id_1 docker_id_2 docker_id_3 ==> Will delete multiple dockers
sudo docker ps -a ==> cmd will list the available containers on the present server
sudo docker rm container_id ==> cmd will delete a single specific container present in the machine
sudo docker rm container_id_1 container_id_2 container_id_3 ==> will delete multiple containers
docker system prune -a ==> It will clear space on your device by doing the following tasks
This command will remove:
- all stopped containers
- all networks not used by at least one container
- all images without at least one container associated with them
- all build cache
Ø sudo
dmesg: dmesg contains
all kernel-related information (loading /unloading, module loading, firmware
loading, etc. lot of information).
Ø sudo dmesg | grep -i error if you search like this, it will
give kernel/firmware-related error messages
Ø Any kernel-related error & other information you want
to see, then you must run sudo dmesg from the home directory,
su sudo dmesg -C --> It will clear all kernel error messages
Ø
cd
/var/log/ èin this folder, the dmesg log file
& other kernel log files are present.
èFirmware not loaded/ kernel crashed. All information you can use the command sudo dmesg | grep -i error to see the error messages.
