Get the CA for curl

curl.sh

# 1 get the cert
echo quit | openssl s_client -showcerts -servername server -connect example.com:443 > example.com.pem
# 2 use it in curl command to test it
curl --cacert example.com.pem https://example.com
# 3 add it to your certificates store (Debian)
sudo mv example.com.pem /usr/share/ca-certificates/example.com.crt
# 4 update the store
sudo dpkg-reconfigure ca-certificates
# 4 bis
sudo update-ca-certificates --fresh