環境
- Debian 9 (stretch) on GCE
GCE の Debian で運用してたときに apt update
したら cloud-sdk まわりでエラーがでた。
Err:6 http://packages.cloud.google.com/apt cloud-sdk-stretch InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6A030B21BA07F4FB
Err:8 http://packages.cloud.google.com/apt google-compute-engine-stretch-stable InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6A030B21BA07F4FB
Err:9 http://packages.cloud.google.com/apt google-cloud-packages-archive-keyring-stretch InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6A030B21BA07F4FB
なんかの key が無効になったらしいので改めて追加
$ curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -