How to create a self signed or official ssl tls certificate without questions asked (non-interactive) on the command line interface


  • create a x509 server certificate for use in TLS (ssl)
  • self signed (not official, not trusted by default)
  • includes multiple alternative (alias) DNS hostnames (virtual hosts)
  • includes administrative email contact
  • create new or reuse a host's private key
  • non interactive (no questions asked)
  • no passphrases for private key
  • works on UBUNTU 20.04 LTS and similar

Generate self signed server certificate incl. new private key

To create a new private key + self signed certificate use:

openssl req \
  -x509 \
  -sha256 \
  -nodes  \
  -days 3650 \
  -newkey rsa:4096 \
  -keyout youtHostnameHere.key \
  -out youtHostnameHere.SELFSIGNED.$(date +%F).crt \
  -subj "/C=CountryCode/ST=StateCode/L=LocationCity/O=yourOrganisationOrFqdn/OU=yourOrganisationalUnitOrFqdn/" \
  -addext \
  -addext 'subjectAltName=DNS:*' \

To read/show a certificate in human readable format use:

openssl x509 -text -noout -in yourNewCertificateFileToDisplay | more

Generate (unprotected) private key only:

openssl genrsa -out yourFqdnHostname.key 2048

To view/show private key in a more human readable format use:

openssl rsa -text -in ourFqdnHostname.key  | more

Request official server certificate using existing private key (csr)

openssl req \
  -new \
  -key yourKeyFile.key \
  -out youtHostnameHere.SELFSIGNED.$(date +%F).crt \
  -subj "/C=CountryCode/ST=StateCode/L=LocationCity/O=yourOrganisationOrFqdn/OU=yourOrganisationalUnitOrFqdn/" \
  -addext \
  -addext 'subjectAltName=DNS:*' \

To view/show CSR in human readable format use:

openssl req -text -noout -in yourCsrFileHere.csr | more

Self sign a given csr

:!: WARNING: This does NOT pass through the alternative DNS hostnames to the certificate!!! Also the -addext option is not available within x509 context. So this section is mostly useless atm. For better control set up a full blown CA and use the openssl ca context instead.

openssl x509 \
  -days 3650 
  -in yourCsrFileHere.csr
  -signkey yourKeyFile.key
  -out youtHostnameHere.SELFSIGNED.$(date +%F).crt 

it-artikel/linux/how-to-create-a-self-signed-or-official-ssl-tls-certificate-without-questions-asked-non-interactive-on-the-command-line-interface.txt · Last modified: 2021-04-01 19:43 by