session-64.txt

init containers
ephemeral volumes
	emptyDir
	hostPath
Liveness probe
readiness probe

Init containers
--------------
1. Init containers run before the main containers run. It can be one or many
2. Init containers should be completed one by one.
3. If init containers fail main containers will not run.
Init containers always run to completion.
4. to wait until other applications are ready, to prepare some configuration for main container.

DB and backend both are started at a time. backend is ready before DB started successfully. backend is getting failed because no connection to DB.

we can have init container for backend. so before backend starts init container should be checking if DB is ready or not.

1. without root user
2. use volumes
3. use official images
4. use small images, dont keep unnecessary installations
5. use multi stage builds
6. use health checks
7. use custom network
8. reduce imaging layers
9. use autoscaling

readiness probe
-------------------
we can define when our container is ready.
for backend we can say when port 8080 opened, we can say
it is ready

liveness probe
-----------------
health check
once container is ready, then only we can do health check
auto healing

liveness proble will happen frequently, whenever it finds
something is wrong it will auto restart the container.

ephemeral volumes
	emptyDir
	hostPath

static provisioning and dynamic provisioning --> perm volumes

ephemeral volumes
--------------------
1. pod is running and generating log. does it generate log after terminated?
/var/log/nginx/access.log
/var/log/nginx/error.log

ephemeral volumes --> emptyDir

1. nginx --> main container
2. filebeat --> sidecar

you should somehow mount the volume/storage to both containers.

by default k8 considers volumes as emptyDir.


docker run -d -v /:/spam nginx

daemon set
------------------
daemonset will make sure a pod runs in every node. why this is useful?

we have to access underlying node logs and push them to elastic search for log monitoring. if we run deamonset in kubernetes, it make sure a pod is automatically created when new node is added.

zeal vora --> AWS security specialist