Given a CA certificate file certificate.crt, follow these steps to install it on Ubuntu:

1. Create a directory for extra CA certificates in /usr/share/ca-certificates:

   sudo mkdir /usr/share/ca-certificates/extra
   

2. Copy the CA .crt file to this directory:

   sudo cp certificate.crt /usr/share/ca-certificates/extra/certificate.crt
   

3. Let Ubuntu add the .crt file’s path relative to /usr/share/ca-certificates to /etc/ca-certificates.conf:

   sudo dpkg-reconfigure ca-certificates
   

In case of a .pem file on Ubuntu, it must first be converted to a .crt file:

openssl x509 -in certificate.pem -inform PEM -out certificate.crt

For Citrix Reciever:

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