kali更新时无法安全地用该源进行更新，所以默认禁用该源。
先附上各种源 （其实系统本身就自带了更新源，去掉其注释也是可以的，现在官方源的下载速度也还ok，下面的三选一亦可）
#kali官方源
deb http://http.kali.org/kali kali-rolling main non-free contrib
#中科大的源
deb http://mirrors.ustc.edu.cn/kali kali-rolling main non-free contrib
deb http://mirrors.ustc.edu.cn/kali kali-rolling main contrib non-free
deb-src http://mirrors.ustc.edu.cn/kali kali-rolling main contrib non-free
deb http://mirrors.ustc.edu.cn/kali-security kali-current/updates main contrib non-free
deb-src http://mirrors.ustc.edu.cn/kali-security kali-current/updates main contrib non-free
#阿里云源
deb http://mirrors.aliyun.com/kali kali-rolling main non-free contrib
deb http://mirrors.aliyun.com/kali-security/ kali-rolling main contrib non-free
deb-src http://mirrors.aliyun.com/kali-security/ kali-rolling main contrib non-free
apt-get update
apt-get upgrade
apt-get dist-upgrade
apt-get clean
或者apt-get clean && apt-get update -y （默认全y）
发现apt-get update的时候还是无法安全地用该源进行更新，所以默认禁用该源。
可能时/etc/apt/sources.list.d 下某个仓库出现了问题，删除掉就可以了