root@srv:/var/www/html# apt-get update
Get:1 http://security.ubuntu.com trusty-security InRelease [83 B]
Err http://security.ubuntu.com trusty-security InReleasets/partial/security.ubuntu.com_ubuntu_dists_trusty-security_InRelease into data and signature failed

Fetched 83 B in 0s (817 B/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://security.ubuntu.com trusty-security InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/InRelease

W: Some index files failed to download. They have been ignored, or old ones used instead.
root@srv:/var/www/html#


root@srv:/var/www/html# cat /etc/apt/sources.list
deb http://security.ubuntu.com/ubuntu trusty-security main restricted
deb-src http://security.ubuntu.com/ubuntu trusty-security main restricted
deb http://security.ubuntu.com/ubuntu trusty-security universe
deb-src http://security.ubuntu.com/ubuntu trusty-security universe
deb http://security.ubuntu.com/ubuntu trusty-security multiverse
deb-src http://security.ubuntu.com/ubuntu trusty-security multiverse

root@srv:/var/www/html#