今天在debian/ubuntu下运行apt update刷新更新源的时候却遇到 “There is no public key available for the following key IDs” 的问题，具体表现为以下错误提示：

W:There is no public key available for the following key IDs: 3B4FE6ACC0B21F32,
W:There is no public key available for the following key IDs: 3B4FE6ACC0B21F32,

直接简单的解决方案：

apt-get install debian-keyring debian-archive-keyring

apt-key update