I want to put some local machines with fixed IP addresses into /etc/hosts.

This is on a Raspberry Pi running Raspbian (Debian) Trixie.

In the default /etc/hosts I find a message suggesting that I should make
my changes in /etc/cloud/templates/hosts.debian.tmpl instead, or to
disable the management of /etc/hosts by cloud-config.

Now, I'm not doing anything that requires cloud-config, so disabling it
would be fine -- but it seems a little drastic -- so bear with me.

In /etc/cloud/templates/hosts.debian.templ there is a line that reads

127.0.0.1 {{fqdn}} {{hostname}}

The idea is that {{fqdn}} will get replaced by myhostname.mydomain and {{hostname}} will be replaced by myhostname (from /etc/hostname, I guess).

The trouble is, at boot time when /etc/hosts is generated from this
template the system doesn't know my domain name, so the resultin line in /etc/hosts reads:

127.0.0.1 myhostname myhostname

which is not what I want to see!

The suggestion I get from extensive searching online is that the domain
name should come from /etc/resolv.conf ... but when I look into /etc/resolv.conf I see

# Generated by NetworkManager

which is a fair warning that NetworkManager may rewrite that file
without warning, and without preserving any changes I may have made.

More extensive reading with $SEARCH_ENGINE leads me to understand that NetworkManager gets the domain name that it uses from .... (you guessed
it) /etc/hosts

The whole thing runs round in circles ...

There is some suggestion that one can put a FQDN instead of a simple
server name into /etc/hostname, but this suggestion is roundly condemned
by almost everyone.

So ... how do I tell cloud-config (or whatever it is that is rewriting
my /etc/hosts at every boot) what my domain name is?

As I said: This is not a dynamically-generated VM or a cloud server
instance, it's a Raspberry Pi sitting on my desk. It's configuration
isn't going to change with the direction of the wind. It's not the sort
of installation for which cloud-config was conceived, and I'm slightly surprised that package is part of the installation (it isn't on my x64
desktop machine running Debian Trixie). For my own purposes disabling
the update of /etc/hosts or hard-coding the domain in the template will suffice ... but what's the *right* answer.


--
Cheers,
Daniel.


--- MBSE BBS v1.1.7 (Linux-x86_64)
* Origin: Daniel James (2:250/1@fidonet)

Daniel James <daniel@me.invalid> writes:

I want to put some local machines with fixed IP addresses into /etc/hosts.

[...]

As I said: This is not a dynamically-generated VM or a cloud server
instance, it's a Raspberry Pi sitting on my desk. It's configuration
isn't going to change with the direction of the wind. It's not the
sort of installation for which cloud-config was conceived, and I'm
slightly surprised that package is part of the installation (it isn't
on my x64 desktop machine running Debian Trixie). For my own purposes disabling the update of /etc/hosts or hard-coding the domain in the
template will suffice ... but what's the *right* answer.

AFAICT the right answer in your use case is to remove cloud-init.

--
https://www.greenend.org.uk/rjk/

--- MBSE BBS v1.1.7 (Linux-x86_64)
* Origin: terraraq NNTP server (2:250/1@fidonet)

On 08/02/2026 17:47, Richard Kettlewell wrote:

AFAICT the right answer in your use case is to remove cloud-init.

Yes, that would seem about right. I'm not quite sure what /else/ might
be removed if I apt remove it, but I'm sure I'll find out.

Thanks.

--
Cheers,
Daniel.

--- MBSE BBS v1.1.7 (Linux-x86_64)
* Origin: Daniel James (2:250/1@fidonet)