How long can hostname be

Add a comment. Active Oldest Votes. Maximum name length 15 characters. DNS computer names : Minimum name length 2 characters. Maximum name length 63 characters. Improve this answer. You might however create host headers for a web site hosted on a computer and that is then subject to this recommendation. This seems to have changed. I just set up Windows Server and it would allow me to enter a name with a length greater than 15, but it does warn that the hostname will then differ from the NetBIOS name.

I'm not going to risk that complication, but it seems like I'd be allowed to. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. In addition is there any defined variable that can be used in Unix programming to call that number? In addition, you can generally include limits. While the POSIX standard says it is guaranteed not to exceed bytes, that does not necessarily mean that each implementation will adhere to that.

Code should deal with hostnames up to bytes long; administrators should keep hostname length excluding domain within 19 bytes, and domain name length excluding hostnames within 23 bytes.

There are other limits that come into play when you are using hostnames that will be used in DNS, as hostnames in SSL certificates or e-mail addresses. A label consists of a length octet followed by that number of octets representing the name itself".

With these length prefixes including the one for the final length zero label , the actual limit for a fully qualified domain name is bytes. Appendix A. If a hostname will be used in e-mail addresses for OpenSSL-generated certificates, the and username will also need to fit within 40 bytes the "less than" in the error should really be "no more than" , which for a maximum username length of 8 bytes, implies a maximum hostname FQDN length of 31 bytes.

If the maximum username length is longer than 8 bytes, the maximum hostname length is decreased accordingly - the modern Linux limit of 32 would give a maximum FQDN length of 7 that is impractical, even for URL shortening services like bit.

There is a separate upper bound ub-emailaddress-length of bytes in RFC , increased to bytes in RFC ; this is actually for another, legacy embedding of e-mail addresses in X.

Taking the minimum of all these maximums and a median. According to RFC the length of a FQDN is limited to characters, and each label node delimited by a dot in the hostname is limited to 63 characters, so in effect the limit you're after is Hostnames are generally limited to bytes. Git 2. See commit a9a 18 Apr by David Turner csusbdt. Merged by David Turner -- csusbdt -- in commit a9a , 19 Apr Export the fallback definition from daemon. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

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