[Linux] apt-get update PUBKEY 에러 (he following signatures couldn't be verified because the public key is not available: NO_PUBKEY FEEA9169307EA071 NO_PUBKEY 8B57C5C2836F4BEB)

apt-get update 시 아래와 같이 NO_PUBKEY 에러가 발생 했을 시 

$ apt-get update
Get:1 https://download.docker.com/linux/ubuntu xenial InRelease [66.2 kB]
Hit:2 http://security.ubuntu.com/ubuntu xenial-security InRelease
Hit:3 http://kr.archive.ubuntu.com/ubuntu xenial InRelease
Hit:4 http://kr.archive.ubuntu.com/ubuntu xenial-updates InRelease
Err:5 https://apt.kubernetes.io kubernetes-xenial InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FEEA9169307EA071  NO_PUBKEY 8B57C5C2836F4BEB

각 repository의 PUBKEY를 내려받아 업데이트 진행 하면 해당 에러를 해결 할 수 있다.

아래 명령어를 이용해서 PUBKEY가 없는것들을 업데이트 진행

$ apt-key adv --keyserver keyserver.ubuntu.com --recv-keys FEEA9169307EA071 8B57C5C2836F4BEB

Executing: /tmp/tmp.FDbTelwgVX/gpg.1.sh --keyserver
keyserver.ubuntu.com
--recv-keys
FEEA9169307EA071
8B57C5C2836F4BEB

이후 다시 apt-get update를 통해 정상동작하는것을 확인

$ sudo apt-get update
Get:1 https://download.docker.com/linux/ubuntu xenial InRelease [66.2 kB]
Hit:2 http://security.ubuntu.com/ubuntu xenial-security InRelease
Hit:3 http://kr.archive.ubuntu.com/ubuntu xenial InRelease
Hit:4 http://kr.archive.ubuntu.com/ubuntu xenial-updates InRelease
Get:5 https://apt.kubernetes.io kubernetes-xenial InRelease [154 B]
Hit:6 http://kr.archive.ubuntu.com/ubuntu xenial-backports InRelease
Get:7 https://apt.kubernetes.io kubernetes-xenial/main amd64 Packages [52.6 kB]