今天在維護一台 EasyEngine VPS 時，做 apt-get update 升級指令時，發生 PGP keys are expired 的錯誤，Linux 為 Ubuntu 16.04 LTS 系統。

錯誤回應為：

Err:10 http://download.opensuse.org/repositories/home:/rtCamp:/EasyEngine/xUbuntu_16.04  Release.gpg
  The following signatures were invalid: KEYEXPIRED 1501595774
Fetched 1,498 B in 1s (1,446 B/s)
Reading package lists... Done
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://download.opensuse.org/repositories/home:/rtCamp:/EasyEngine/xUbuntu_16.04  Release: The following signatures were invalid: KEYEXPIRED 1501595774
W: Failed to fetch http://download.opensuse.org/repositories/home:/rtCamp:/EasyEngine/xUbuntu_16.04/Release.gpg  The following signatures were invalid: KEYEXPIRED 1501595774
W: Some index files failed to download. They have been ignored, or old ones used instead.

修正的方法

先檢查你的防火牆，有沒有封鎖 11371 / TCP port，有的話，請打開這個端口。

運行下面的指令

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv 3050AC3CD2AE6F03

回應

Executing: /tmp/tmp.CmN7tDjbK0/gpg.1.sh --keyserver
keyserver.ubuntu.com
--recv
3050AC3CD2AE6F03
gpg: requesting key D2AE6F03 from hkp server keyserver.ubuntu.com
gpg: key D2AE6F03: "home:rtCamp OBS Project <home:rtCamp@build.opensuse.org>" 1 new signature
gpg: Total number processed: 1
gpg:         new signatures: 1

PGP keys 的有效期已經延長，apt-get update 就可以繼續更新了。

參考資料：

Repo Key Expired Error for EasyEngine on Ubuntu 16.04

http://community.rtcamp.com/t/repo-key-expired-error-for-easyengine-on-ubuntu-16-04/9227

Your PGP keys are expired for custom nginx build (16.04)

https://github.com/EasyEngine/easyengine/issues/893