Re: Domain name to use on home networks

[Pocket <pocket@columbus.rr.com>]

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On Oct 27, 2023, at 10:00 AM, Andrew M.A. Cater <amacater@einval.com> wrote:

On Fri, Oct 27, 2023 at 09:30:09AM -0400, Pocket wrote:

Sent from my iPad

On Oct 27, 2023, at 9:05 AM, Greg Wooledge <greg@wooledge.org> wrote:

On Fri, Oct 27, 2023 at 07:59:00AM -0400, Pocket wrote:

On 10/27/23 07:50, Greg Wooledge wrote:

On Fri, Oct 27, 2023 at 07:29:20AM -0400, Pocket wrote:

/etc/hosts

If you're using short-form hostnames like this:

unicorn:~$ hostname

unicorn

then yeah, that's all you need.  If you're using long-form hostnames

(with dots in them), then you also need to configure /etc/hostname.

hostnamectl set-hostname is the command to do it - and will survive a reboot.

Andy

From the man page

THE FQDN

The FQDN (Fully Qualified Domain Name) of the system is the name that the resolver(3) returns for the host name, such as, ursula.example.com. It is usually the hostname followed by the DNS domain name (the part after the first dot). You can check the FQDN using hostname --fqdn or the domain name using dnsdomainname.

You cannot change the FQDN with hostname or dnsdomainname.

The recommended method of setting the FQDN is to make the hostname be an alias for the fully qualified name using /etc/hosts, DNS, or NIS. For example, if the hostname was "ursula", one might have a line in /etc/hosts which reads

127.0.1.1 ursula.example.com ursula

Technically: The FQDN is the name getaddrinfo(3) returns for the host name returned bygethostname(2). The DNS domain name is the part after the first dot.

Therefore it depends on the configuration of the resolver (usually in /etc/host.conf) how you can change it. Usually the hosts file is parsed before DNS or NIS, so it is most common to change the FQDN in /etc/hosts.

If a machine has multiple network interfaces/addresses or is used in a mobile environment, then it may either have multiple FQDNs/domain names or none at all. Therefore avoid usinghostname --fqdn, hostname --domain and dnsdomainname. hostname --ip-address is subject to the same limitations so it should be avoided as well.