/dev/chat

5:23 PM

don

@terdon Did you find unix.stackexchange.com/questions/235909/… was completely useless? I think it actually added some detail to the bland answer there which has 1 vote. Not really a nice welcome for a user answering the first time...

@Kamal Well, it was flagged as not an answer and I felt the flag was right. You weren't answering the question, really. That was more of a comment:

> I got a very similar host name yesterday while connected over Wi-Fi to a university campus network. Once disconnected, my Mac got his "normal" host name back. (Verified before and after disconnecting by running hostname on the command line).
It might be some commercial DHCP server that uses that as the default naming convention for hosts joining the network.

The only bit that could be an answer was the last sentence but without an explanation or even a suggestion on how to do anything about it, it didn't seem very useful.

Hmm. I admit I hadn't read the question as carefully as I should have. On second thought, I think you're right and it does offer some useful information. I still feel it isn't an answer though (ideally, an answer would be an explanation of what happened and why, as well as a solution to the problem). But it is relevant. So I'll just convert it into a comment.

Well the other answer only mentions it's host name (which is pretty obvious, but whatever). I said the same, plus explaining why it might have gotten that specific host name

@Kamal The other answer is pretty bad, yes. But we don't see that when dealing with flags. All we get is the text of the post that was flagged.

OK, fair enough. In absence of a way to know why certain host names might be assigned, that's better than nothing though

Thanks for converting the answer – as I cannot comment yet :)

5:29 PM

Yep, which is why I converted both into comments.

Now, I must say I really hope you're wrong here (I believe you, I just don't get it). I can't imagine why or how a DHCP server could affect your local hostname!

Then again, networking really isn't my strong suit, so I may be missing something very obvious. It does sounds like a pretty huge security hole to my non-expert ears.

@Kamal No problem. And feel free to ping a mod in chat or post a meta question if you disagree with any mod actions. We're only human, after all, and have been known to make mistakes :)

As long as you're civil about it, as you were just now, feel very free to ask about any mod action.

A: How to get the hostname from a DHCP server

In certain conditions, it's not unusual for a DHCP server to serve the host name together with the IP

You can get your hostname from your DHCP server - it is part of the DHCP specification. https://tools.ietf.org/html/rfc1533#section-3.14 "This option specifies the name of the client"

@terdon The DHCP server can reply to a request with a host name, and the host may take it and use it as an hostname (just as is done with router settings etc.). I can't say that I've seen this actually done (by default) on any of the machines I've been running though.

Ah, yes, that's different. If there something running on the client that sets the hostname based ion the DHCP information, that can make sense.

I guess you can disable it at the DHCP client level, if you don't want your host name to (temporarily) change

I think Mac OS X does that, if you haven't otherwise set a hostname.

5:35 PM

I was thinking that the DHCP server was somehow making changes in the client machine itself.

I think Network Manager probably does too...

Thanks again @terdon! Will certainly do. Have a great day everyone

@terdon No, it can't.

I know debian-installer does it, when installing

@Kamal See you :)

@Kusalananda Good

5:37 PM

(Personally, that seems like the start of a good answer—it needs a little cleanup, and it'd be nice if it included how to override it on the client)

I've had the opposite problem, where I've been wanting a client machine to use the name provided to it by a DHCP server. It was diskless clients. I believe I gave up on it.

@Kusalananda default dhclient config requests it, would be as simple as plopping a script in /etc/dhcp/dhclient-exit-hoks.d

... on Linux, yes.

@Kusalananda I'm sure xBSD has something similar, probably using the ISC DHCP client too...

@derobert I'm sure the one I'm using can be scripted somehow, but it's not something I'm interested in doing right now.

5:43 PM

Hmmm, I just checked: at least on Debian, if the hostname is (none), localhost, or blank, then it takes the DHCP host name. But I'm not sure if that's ISC DHCP client default, or a Debian-specific patch

@Kamal @terdon Anyway, I'd suggest that an answer mentioning how the prompt comes from PS1, and how \h in PS1 means host name—and then how that can be set by DHCP would answer that question. And of course if you know, how to turn off hostname set by DHCP on Mac OS X.

@derobert Sounds like a good start.

Edited my answer, if you guys want to have a look...

Don't think I can add more detail than that :)

@Kamal I'd vote to undelete, but that's apparently not possible on mod-deleted answers... so we need @terdon

Thanks, I'm done for the day ;) I'll leave the fate of that answer to the powers that be :D