A CSR (Certificate Signing Request) is a block of encoded text sent to a Certificate Authority (CA) when ordering an SSL. It contains a cryptographic public key and your organization’s details. To generate a CSR on a Linux server using OpenSSL: ```bash openssl req -new -newkey rsa:2048 -nodes -keyout example.com.key -out example.com.csr ``` The command will prompt you to enter details: Country Name, State, Locality, Organization Name, Organizational Unit, Common Name (e.g., example.com), Email Address, etc. Upon completion, example.com.key is your private key and example.com.csr is the request file you submit to the CA. Keep your private key secure and never share it.