docker-volumes1

in simple terms volume can be referred as  directory
inside the container


we can access the volume after stopping the container as well

volume will be created in one container and can be accessed
by other containers

you can define the volume to a container while you're
creating the container


a volume can be shared across any number of containers

when you create a image out of a running container, and when container is created out of it, the volume is avialble in newly created container


Benefits of volumes
---------------------

Decoupling container from storage

Share volumes among different containers

Attach volumes to containers

on deleting container volume doesnt get deleted


FROM ubuntu
VOLUME ["/myvolume"]

docker build -t imagename .

create container out of the image

docker run -it --name container2 --privileged=true --volumes-from container1 ubuntu /bin/bash


now after creating container2(new)
myvolume1 is visible whatever you
can do in volume

touch /myvolume1/samplefile

docker start container1

docker attach container1

ls /myvolume1
-------------------------------
while creating a container itself if you
want to attach the volume

docker run -it --name cont-name
-v /volume ubuntu /bin/bash
we are telling in the root directory
create a directory as volume2



docker run -it --name cont4
--priveledged=true --volumes-from cont-name
 ubuntu /bin/bash













Docker volumes
------------------------
anything  data that is put in volume, can be shared to other container
and by sharing the volume






The data is no longer available when the the container 
dies, using docker volumes we can persist data even after contianer
dies

with the volumes we can persist the data
even after the container dies

when the container dies, the volumes are untouched


* Normal Volumes

* Bind Volumes

* Anonymous volumes


all data created in temp layer is deleted 
why docker volumes are so important
-------------------------------------

docker run -d --name mysql -e "MYSQL_ROOT_PASSWORD=12345678"
mysql:8

docker ps

docker exec -it container-id bash


mysql -u root -p12345668

show databases;

create database prod_db;

show databases;

save/ persist data 

docker volumes ---->


------------------------------------------------------------------------------
--> a running container conent can be modified.

-->as storage of docker is ephermal by default, its lost
after restart

--> Any modifications are done to a running container are
written to read/writable filesystem layer by default that is
removed when the container is stopped.

R/W FILE system LAYER should not be used for persistent storage, as it doest perform well

-->Docker keeps ephermal storage for sometime after container is stopped
making it easier to troubleshoot based on information logs


persistent storage can be offered by using a host directory

the container will bind mount to this host directory to write and access 
persistent data

----------------------------------

mkdir -p /var/local/mysql
chown -R 27:27 /var/local/mysql
docker pull mariadb

docker run --name mariadb:latest -d -v /var/local/mysql:/var/lib/mysql
-e MYSQL_USER=user -e MYSQL_PASSWORD=password -e MYSQL_DATABASE=addresses -e MYSQL_ROOT_PASSWORD=password mariadb


ls -l /var/local/mysql


docker exec -it mariadb /bin/bash

ls -l /var/lib/mysql