How to use the "prompt=yes" mode of the OpenSSL "req -new" command? I want to enter DN values at the command prompt.

You can use "prompt=yes" mode of the OpenSSL "req -new" command as shown below, if you set "prompt=yes" and provide DN (Distinguished Name) field prompts in the configuration file.

C:\Users\fyicenter>type test.cnf
# unnamed section of generic options
default_md = md5

# default section for "req" command options
[req]
input_password      = fyicenter
prompt              = yes
distinguished_name  = my_req_dn_prompt

[my_req_dn_prompt]
commonName             = Common Name
countryName            = Country Name
stateOrProvinceName    = State
localityName           = City
organizationName       = Organization
organizationalUnitName = Department
emailAddress           = Email

C:\Users\fyicenter>\local\openssl\openssl.exe

OpenSSL> req -new -key rsa_test.key -out test.csr -config test.cnf
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Common Name []:FYIcenter.com CA
Country Name []:US
State []:NY
City []:New York
Organization []:FYIcenter.com
Department []:IT
Email []:ca@fyicenter.com
   
OpenSSL> req -in test.csr -text -noout
Certificate Request:s
    Data:
        Version: 0 (0x0)
        Subject: CN=FYIcenter.com CA, C=US, ST=NY, L=New York, O=FYI Center, OU=IT
                 /emailAddress=ca@fyicenter.com
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (1024 bit)
...

As you can see from the output, the "req -new" command executed correctly in the "prompt=yes" mode. distinguished_name section options are used as DN field prompts.

⇒ OpenSSL "req" - "prompt=yes" Mode with DN Validations

⇐ OpenSSL "req" - "prompt=no" Mode

⇑ OpenSSL "req" Command

⇑⇑ OpenSSL Tutorials