Help with proper FQDN naming

January 5, 2016 1.5k views
Linux Commands Ubuntu
tpdietz
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tpdietz

We have purchased an SSL certificate and need to provide the CSR. From reading earlier postings, I believe I have the correct command for doing that. However, I am confused as to what to use for the Common Name. It says "server FQDN or YOUR name". I don't know what they mean by YOUR name (if someone cares to explain, i'll be happy to read it), so I'll focus on the FQDN.

I am running Ubuntu 14.04. For this question, I will use mydomain.com as our domain name.

When I run hostname, I get "mydomain" as the response. the /etc/hostname file looks like:

127.0.0.1 localhost mydomain mydomain.com www.mydomain.com

When I enter 'hostname -f', I get 'localhost'. Should I set my FQDN to mydomain.com or mydomain.mydomain.com (or something else)?

Thanks.

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2 Answers
brass January 5, 2016

if you dns is setup correctly a host lookup for your domain name should come back with 

# host domain.com
domain.com has address of 192.168.1.1

IP address is just representative of your IP. If the dns is set up properly then put in your FQDN for the common name.

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azaraks January 6, 2016

I got no idea what is the 'earlier posting' you read.
But if your ssl certificate is for aaa.domain.com, then you will have to input aaa.domain.com.

  • No, you cannot use a cert for aaa.domain.com with bbb.domain.com.
  • Yes, a single cert can represent multiple DN. (subjectAltName)
  • Yes, there is a 'wild-card' cert, which can fit *.domain.com.
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