Why letsencrypt showing error?

问题

I am trying to install letsencrypt on ubuntu 14 on DigitalOcean Server but getting this issue.

I tried sudo to install but same error, also try to install libs but nothing happen.

apt-key update result :

gpg: key 437D05B5: "Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>" not changed
gpg: key FBB75451: "Ubuntu CD Image Automatic Signing Key <cdimage@ubuntu.com>" not changed
gpg: key C0B21F32: "Ubuntu Archive Automatic Signing Key (2012) <ftpmaster@ubuntu.com>" not changed
gpg: key EFE21092: "Ubuntu CD Image Automatic Signing Key (2012) <cdimage@ubuntu.com>" not changed
gpg: Total number processed: 4
gpg:              unchanged: 4

回答1:

You need to install (or update) the public key(s) used to verify the packages.

Do this:

apt-key update
apt-get update

回答2:

You can find answer here : https://askubuntu.com/questions/102153/untrusted-package-errors-after-installing-security-tools

But easy thing just use these commands :

apt-get autoclean
apt-get --purge autoremove
apt-get dist-upgrade

This may solve your issue or look into link.

来源：https://stackoverflow.com/questions/37156021/why-letsencrypt-showing-error