Certificate error when using Citrix Receiver.

By default, Citrix Receiver only trusts a few root CA certificates, which causes connections to many Citrix servers to fail with an SSL error.

The ca-certificates package (already installed on most Ubuntu systems) provides additional CA certificates in /usr/share/ca-certificates/mozilla/ that can be conveniently added to Citrix Receiver to avoid these errors:

sudo ln -s /usr/share/ca-certificates/mozilla/* /opt/Citrix/ICAClient/keystore/cacerts/ 
 
sudo c_rehash /opt/Citrix/ICAClient/keystore/cacerts/