Tengo un problema con la descarga de docker en el servidor ubuntu.

si pongo:

 curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

Yo obtengo :

 curl: (60) SSL certificate problem: unable to get local issuer certificate More details here: https://curl.haxx.se/docs/sslcerts.html curl failed to verify the legitimacy of the server and therefore could not establish a secure connection to it. To learn more about this situation and how to fix it, please visit the web page mentioned above.

Lo busco en Google y pruebo varios pensamientos como:

 sudo apt install apt-transport-https ca-certificates curl software-properties-common sudo apt-get install ca-certificates

pero nada ayuda,...

si lo hago

 cd /etc/ssl/certs/; wget https://curl.haxx.se/ca/cacert.pem.sha256; shasum -c cacert.pem.sha256; rm -f cacert.pem.sha256

Yo obtengo :

 --2019-06-03 12:19:31-- https://curl.haxx.se/ca/cacert.pem.sha256 Resolving curl.haxx.se (curl.haxx.se)... 151.101.194.49, 151.101.130.49, 151.101.66.49, ... Connecting to curl.haxx.se (curl.haxx.se)|151.101.194.49|:443... connected. ERROR: cannot verify curl.haxx.se's certificate, issued by 'emailAddress=our.email,...OU=..,L=..ST=,..NC=..,O=..C=..': Unable to locally verify the issuer's authority. To connect to curl.haxx.se insecurely, use `--no-check-certificate'.

¿Cómo resuelvo esto y cómo encuentro el certificado que fue firmado por nuestro correo electrónico,...