running ssh workflow on group of servers

#generate sample servers

for i in {1..110}; do printf "myserver%05d\n" $i; done > myservers.txt

#group servers by 20
count=0
group=0
for line in $(cat  myservers.txt);
do
  printf "GROUP_%03d %s\n" $group $line
  ((count=$count + 1))
  if [ $count -eq 20 ]; then
    ((group=$group + 1))
    count=0
  fi
done >> grouped.txt

#print servers in given group
cat grouped.txt | grep GROUP_005 | awk -F' ' '{print $2}'


#put this in steps.sh

myserver=$1
step=$2


case $step in
  1)
    echo "hello, this is step 1 for server $myserver"
    ;;
  2)
    echo "ciao, this is step 2 for server $myserver"
    ;;
  3)
    echo "Gruezi, this is step 3 for server $myserver"
    ;;
  *)
    echo "ERROR invalid step $step"
esac

#execute given step for GROUP

THESTEP=3; cat grouped.txt | grep GROUP_005 | awk -vstep="$THESTEP" -F' ' '{print $2,step}' | xargs ./steps.sh

saltstack getting started

curl -L https://bootstrap.saltstack.com -o install_salt.sh

sudo sh install_salt.sh -M #install master and minion on same node

/etc/salt

/etc/salt/minion
master: localhost
id: myminion

sudo systemctl restart salt-minion
sudo systemctl restart salt-master
sudo salt-key
sudo salt-key -a myminion (then type Y)

sudo salt '*' test.ping

sudo salt-call sys.doc test.ping

sudo salt '*' cmd.run_all 'echo HELLO'

#list matcher
sudo salt -L 'myminion' test.ping

sudo salt '*' grains.item os

sudo salt '*' grains.items

sudo salt --grain 'os:CentOS' test.ping

#custom grains
cat /etc/salt/grains

#list all execution modules
sudo salt '*' sys.list_modules

sudo salt '*' pkg.install htop

sudo salt '*' state.sls apache




Ref:

Colton Meyes - Learning Saltstack (Packt Publishing), really direct and hands-on book.

(PS I had a quick look at "Mastering Saltstack" by Packt, it's waaay too abstract and blablaistic.

https://docs.saltstack.com/en/latest/

ports and pods

#start a pod with default parameters
kubectl run nginx --image=nginx --restart=Never

kubectl describe pod nginx

Node: node01/172.17.0.36
IP: 10.32.0.2

#we can reach nginx with the "IP" address
curl 10.32.0.2:80

but "curl 172.17.0.36:80" doesn't work!

kubectl describe nodes node01
InternalIP: 172.17.0.36


10.32.0.2 is the Pod's IP (=same IP for all containers running in that Pod):
kubectl exec -ti nginx bash
hostname -i
10.32.0.2

The Node IP cannot be used as such to reach the Pod/Container.

Setting the spec.container.ports.containerPort will not change neither the IP nor the POrt at which nginx is running: this parameter is purely "declarative" and is only useful when exposing the Pod/Deployment with a Service.

If you want to "expose" to an IP other than the Pod's IP:

kubectl expose pod nginx --port=8089 --target-port=80

kubectl describe service nginx
Type: ClusterIP
IP: 10.99.136.123
Port: 8089/TCP
TargetPort: 80/TCP
Endpoints: 10.32.0.2:80

NB this IP 10.99.136.123 is NOT the Node's IP nor the Pod's IP. It's a service-specific IP.

curl 10.99.136.123:8089

kubectl get service --all-namespaces

NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
default nginx ClusterIP 10.99.136.123 8089/TCP 16m



Ref:
https://kubernetes.io/docs/concepts/cluster-administration/networking/