Notes

List of assigned IPs in subnet

EC2: List of assigned IPs in subnet

aws ec2 describe-network-interfaces
    --filters "Name=subnet-id,Values=<subnet-id>"
    --query 'NetworkInterfaces[*].PrivateIpAddress'

How to make EC2 user data script run again on startup?

rm /var/lib/cloud/instances/*/sem/config_scripts_user
rm /var/lib/cloud/instance/sem/config_scripts_user

Docker clean up

docker system prune --all --volumes --force

docker volume rm $(docker volume ls -qf dangling=true)

docker rm -vf $(docker ps -aq)
docker rmi -f $(docker images -aq)
docker volume prune -f

Stop all containers

docker stop $(docker ps -qa)

Remove containers

docker rm $(docker ps -qa)

Remove all images

docker images -q  |xargs docker rmi
docker rmi -f $(docker images | grep "<none>" | awk "{print \$3}")

Docker network change default

systemctl stop docker
iptables -t nat -F POSTROUTING
ip link set dev docker0 down
ip addr del 172.17.0.1/16 dev docker0 # delete old route
ip addr add 172.18.32.1/24 dev docker0 # add new one
ip link set dev docker0 up

Permanent options : /etc/default/docker

DOCKER_OPTS : /etc/docker/daemon.json

--bip=172.18.32.1/24 --default-gateway=172.18.32.1

{
 "default-address-pools": [
   {"base":"172.80.0.0/16","size":24},
   {"base":"172.90.0.0/16","size":24}
  ]
}

Export DB dump of a particular database to your machine

$ kubectl exec {{podName}} -n {{namespace}} -- mysqldump -u {{dbUser}} -p{{password}} {{DatabaseName}} > <scriptName>.sql

# Example :
$ kubectl exec mysql-58 -n sql -- mysqldump -u root -proot USERS > dump.sql

Find all images inside containers

kubectl get pods --all-namespaces -o jsonpath="{.items[*].spec.containers[*].image}" |\
tr -s '[[:space:]]' '\n' |\
sort |\
uniq -c

Get Limit Requests for all containers

kubectl get pod --all-namespaces --sort-by='.metadata.name' -o json | \
jq -r '[.items[] | {pod_name: .metadata.name, containers: .spec.containers[] | \
[ {container_name: .name, memory_requested: .resources.requests.memory, cpu_requested: .resources.requests.cpu} ] }]' | \
jq  'sort_by(.containers[0].cpu_requested)'

K8S list all container's image from a cluster

Kube (K8S) list all container’s image from a cluster

kubectl get pods --all-namespaces -o jsonpath="{.items[*].spec.containers[*].image}" |\
tr -s '[[:space:]]' '\n' |\
sort |\
uniq -c

kubectl check secrets certificates

kubectl get secret CERTNAME -o "jsonpath={.data['tls\.crt']}" | base64 -D | openssl x509 -enddate -noout

kubectl basic commands

# connect on Pods
kubectl exec -it --namespace=develop my-pod-id -- /bin/ash
# Show pod network on cluster
kubectl get nodes -o jsonpath='{.items[*].spec.podCIDR}'
# Show Pods by <node>
kubectl get pods --all-namespaces -o wide --field-selector spec.nodeName=<node>
# sorting pods
kubectl get pods -o wide --sort-by="{.spec.nodeName}"

kubernetes volume protected

This happens when persistent volume is protected. You should be able to cross verify this:

Command:

kubectl describe pvc PVC_NAME | grep Finalizers

Output:
Finalizers:    [kubernetes.io/pvc-protection]

You can fix this by setting finalizers to null using kubectl patch:

kubectl patch pvc PVC_NAME -p '{"metadata":{"finalizers": []}}' --type=merge

EKS CPUthrotting

docker run --cpus CPUS -it python python -m timeit -s 'import hashlib' -n 10000 -v 'haslib.sha512().update(b"foo")'

Syntax of IP linux command

ip OBJECT COMMAND
ip [options] OBJECT COMMAND
ip OBJECT help

Understanding ip command OBJECTS syntax OBJECTS can be any one of the following and may be written in full or abbreviated form:

(image)[/posts/introduction/hero.svg]


You can select between IPv4 and IPv6 using the following syntax:

```shell
### Only show TCP/IP IPv4  ##
ip -4 a

### Only show TCP/IP IPv6  ###
ip -6 a

It is also possible to specify and list particular interface TCP/IP details:

### Only show eth0 interface ###
ip a show eth0
ip a list eth0
ip a show dev eth0

### Only show running interfaces ###
ip link show up