更新索引

1
更新索引会碰到如下错误，如果没有报错，可以跳过至下一步

W: GPG error: http://repo.mysql.com/apt/ubuntu xenial InRelease: The following signatures were invalid: KEYEXPIRED 1487236823 KEYEXPIRED 1487236823 KEYEXPIRED 1487236823
1
解决方法如下
1）先查看key，执行命令：apt-key list

/etc/apt/trusted.gpg
--------------------
pub 1024D/437D05B5 2004-09-12
uid Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>
sub 2048g/79164387 2004-09-12

pub 4096R/C0B21F32 2012-05-11
uid Ubuntu Archive Automatic Signing Key (http://www.amjmh.com) <ftpmaster@ubuntu.com>

pub 4096R/EFE21092 2012-05-11
uid Ubuntu CD Image Automatic Signing Key (2012) <cdimage@ubuntu.com>

pub 1024D/FBB75451 2004-12-30
uid Ubuntu CD Image Automatic Signing Key <cdimage@ubuntu.com>

pub 1024D/5072E1F5 2003-02-03 [expired: 2017-02-16]
uid MySQL Release Engineering <mysql-build@oss.oracle.com>