How to Update Kali Linux

If you try to update Kali with

apt-get update

and you see these errors:

W: GPG error: http:// http. kali. org kali Release: The following

 signatures were invalid: KEYEXPIRED 1425567400 KEYEXPIRED 1425567400 

KEYEXPIRED 1425567400 

W: GPG error: http://security. kali. org kali/updates Release: The 

following signatures were invalid: KEYEXPIRED 1425567400 KEYEXPIRED 

1425567400 KEYEXPIRED 1425567400

This is the solution:

rm -rf /var/lib/apt/lists apt-get update
apt-get install kali-archive-keyring apt-get update

Source

http://superuser.com/questions/890383/kali-linux-update-fails