Create a self-signed certificate in one line

$ openssl req -nodes -x509 -newkey rsa:4096 -sha512 -days 365 -keyout cert.key -out cert.pem

Let’s analyze this command:

• req: request a new PKCS#10 certificate;
• -nodes: do not encrypt the private key (no password);
• -x509: output a self-signed certificate instead of a certificate request;
• -newkey rsa:4096: create a new certificate request and a new 4096 bits RSA key;
• -sha512: sign the request with a SHA-512 message digest;
• -days 365: the certificate will be valid for 365 days;
• -keyout cert.key: private key filename;
• -out cert.pem: output filename.