Upgrade procedure

https://www.x-tee.ee/docs/live/xroad/ig-xlb_x-road_external_load_balancer_installation_guide.html#72-online-rolling-upgrade 
 Enable maintenance mode(run from security server) 
 curl http://localhost:5566/maintenance?targetState=true 
 Watch connections and wait until all requests are finished 
 watch -n1 ss -tn state established sport = :5500 or dport = :5500 
 Make snapshot of machine 
 Unhold xroad packages 
 apt-mark unhold xroad-* 
 Update package list 
 apt update 
 Upgrade xroad packages 
 apt install xroad-securityserver-ee 
 Hold xroad packages 
 apt-mark hold xroad-* 
 Disable maintanance mode(run from security server) 
 curl http://localhost:5566/maintenance?targetState=false