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Generate a private key and CSR for multiple domains

cautionSSL and certificatesalle

Caution: This command changes the system. Understand what it does before you run it.

Adjust the values, the command updates live
user@server
openssl req -new -newkey rsa:2048 -nodes -keyout example.com.key -out example.com.csr -subj "/CN=example.com" -addext "subjectAltName=DNS:example.com,DNS:www.example.com"

Creates an unencrypted 2048-bit RSA key and a CSR in the current directory, ready to submit to a certificate authority. -addext adds the domain and its www variant as Subject Alternative Names, which is mandatory today. Afterwards, store the key so that only root can read it.

Note: Existing files with the same name are overwritten without asking. -addext requires OpenSSL 1.1.1 or newer.

Also searched as

  • generate csr with subject alternative names
  • openssl create key and csr one command
  • create certificate signing request linux
  • csr with www and non-www

Related one-liners

All in SSL and certificates

Check the contents of a CSR before submitting it

$openssl req -in example.com.csr -noout -text -verify
harmlessSSL and certificates

Check whether a private key matches a certificate

#openssl x509 -noout -modulus -in /etc/ssl/certs/example.com.crt | openssl md5 && openssl rsa -noout -modulus -in /etc/ssl/private/example.com.key | openssl md5
harmlessSSL and certificates

Read all domains of a certificate (SAN)

$openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -ext subjectAltName
harmlessSSL and certificates

Check the SSL certificate expiration date of a website

$openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -dates
harmlessSSL and certificates

Check whether a certificate expires within the next days

#openssl x509 -in /etc/letsencrypt/live/example.com/cert.pem -noout -checkend $(( 30 * 86400 )) && echo "noch gültig" || echo "läuft bald ab"
harmlessSSL and certificates

Check whether a server supports TLS 1.3

$openssl s_client -connect example.com:443 -servername example.com -tls1_3 </dev/null 2>/dev/null | grep -E "^New,|Protocol *:"
harmlessSSL and certificates

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