why is apt-get update saying can't execute apt-key?

Question

Since upgrading to Ubuntu 16.04.01, every time I try apt-get update, I see:

W: GPG error: http://security.ubuntu.com/ubuntu xenial-security InRelease: Could not execute ‘apt-key’ to verify signature (is gnupg installed?)

With chattr +a /tmp and apt-get -o “Debug::Acquire::gpgv=true” update, I tried rerunning apt-key by hand with the same arguments, and it runs fine.

I created a new droplet with 14.04 and upgraded it to 16.04 and it works fine.

mlv · Accepted Answer

The real answer in my case was that my kernel was way out of date (although for the life of me I can’t understand why that would make any difference). It was failing in execve (returning EPERM). I hadn’t noticed that even though apt-get would install a new kernel, the droplet would never actually use the new kernel.

koaschten · Answer

Curiously I am getting the error right now for a droplet that is reporting it is on 16.04.2 LTS

uname -a

Linux 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

lsb_release -a

No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 16.04.2 LTS Release: 16.04 Codename: xenial

apt-get update

Hit:1 http://us.archive.ubuntu.com/ubuntu xenial InRelease Get:2 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease [102 kB] Err:1 http://us.archive.ubuntu.com/ubuntu xenial InRelease Could not execute ‘apt-key’ to verify signature (is gnupg installed?) Err:2 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease Could not execute ‘apt-key’ to verify signature (is gnupg installed?) Get:3 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB] Err:3 http://security.ubuntu.com/ubuntu xenial-security InRelease Could not execute ‘apt-key’ to verify signature (is gnupg installed?) Fetched 204 kB in 0s (404 kB/s) Reading package lists… Done W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://us.archive.ubuntu.com/ubuntu xenial InRelease: Could not execute ‘apt-key’ to verify signature (is gnupg installed?) W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease: Could not execute ‘apt-key’ to verify signature (is gnupg installed?) W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://security.ubuntu.com/ubuntu xenial-security InRelease: Could not execute ‘apt-key’ to verify signature (is gnupg installed?) W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial/InRelease Could not execute ‘apt-key’ to verify signature (is gnupg installed?) W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease Could not execute ‘apt-key’ to verify signature (is gnupg installed?) W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/InRelease Could not execute ‘apt-key’ to verify signature (is gnupg installed?) W: Some index files failed to download. They have been ignored, or old ones used instead.