ubuntu执行apt-get upgrade报错/usr/bin/mandb: can't remove /var/cache/man/ko/CACHEDIR.TAG: Permission denied

解决办法：为/var/cache/man目录设置所有者、所属组以及添加GUID位

$ sudo chown man:root /var/cache/man -R
$ sudo chmod g+s /var/cache/man -R