debian apt-get update：public key 错误修复
apt-get update 出现 这种错误 Reading package lists… Done W: There is no public key available for the following key IDs: 7638D0442B90D010 W: There is no public key available for the following key IDs: 7638D0442B90D010 W: There is no public key available for the following key IDs: 9D6D8F6BC857C906 解决方法 apt-get install debian-keyring debian-archive-keyring apt-get update