networkmanager hostname woes

networkmanager hostname woes

[Thomas Danckaert]

Hi Guix,

since the change to networkmanager, I've been running into the 
following problem: when I connect to a wireless network using 
networkmanager, I can no longer start graphical applications 
(starting any program fails with “cannot open display :0.0” and 
similar messages).

AFAIU, the cause is that networkmanager changes my hostname (after 
DHCP?), in my case to “new-host2” or something similar, and this 
seems to break the X session.  When I manually restore the hostname 
with “sudo hostname <original-hostname>”, the problem is solved.  Is 
there anyway to disable this behaviour for networkmanager?

Thomas

Re: networkmanager hostname woes

[Christopher Baines]

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On Wed, 13 Sep 2017 12:05:29 +0200 (CEST)
Thomas Danckaert <thomas.danckaert@aeronomie.be> wrote:

> since the change to networkmanager, I've been running into the 
> following problem: when I connect to a wireless network using 
> networkmanager, I can no longer start graphical applications 
> (starting any program fails with “cannot open display :0.0” and 
> similar messages).
> 
> AFAIU, the cause is that networkmanager changes my hostname (after 
> DHCP?), in my case to “new-host2” or something similar, and this 
> seems to break the X session.  When I manually restore the hostname 
> with “sudo hostname <original-hostname>”, the problem is solved.  Is 
> there anyway to disable this behaviour for networkmanager?

I've had this too, it's very frustrating. Luckilly, I think I found a
workaround. I created /etc/hostname and put the machines hostname in
it, and I don't think I've had the issue since.

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Re: networkmanager hostname woes

[Arun Isaac]

Thomas Danckaert writes:

> Hi Guix,
>
> since the change to networkmanager, I've been running into the 
> following problem: when I connect to a wireless network using 
> networkmanager, I can no longer start graphical applications 
> (starting any program fails with “cannot open display :0.0” and 
> similar messages).
>
> AFAIU, the cause is that networkmanager changes my hostname (after 
> DHCP?), in my case to “new-host2” or something similar, and this 
> seems to break the X session.  When I manually restore the hostname 
> with “sudo hostname <original-hostname>”, the problem is solved.  Is 
> there anyway to disable this behaviour for networkmanager?

I have the exact same problem too. If somebody has a solution, I'd like
to hear about it.

Re: networkmanager hostname woes

[Christopher Baines]

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On Thu, 14 Sep 2017 04:57:05 +0530
Arun Isaac <arunisaac@systemreboot.net> wrote:

> Thomas Danckaert writes:
> 
> > Hi Guix,
> >
> > since the change to networkmanager, I've been running into the 
> > following problem: when I connect to a wireless network using 
> > networkmanager, I can no longer start graphical applications 
> > (starting any program fails with “cannot open display :0.0” and 
> > similar messages).
> >
> > AFAIU, the cause is that networkmanager changes my hostname (after 
> > DHCP?), in my case to “new-host2” or something similar, and this 
> > seems to break the X session.  When I manually restore the hostname 
> > with “sudo hostname <original-hostname>”, the problem is solved.
> > Is there anyway to disable this behaviour for networkmanager?  
> 
> I have the exact same problem too. If somebody has a solution, I'd
> like to hear about it.

I created /etc/hostname and put the machines hostname in it, and I
don't think I've had the issue since. Perhaps try that?

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Re: networkmanager hostname woes

[Thomas Danckaert]

From: Alex Sassmannshausen <alex.sassmannshausen@gmail.com>
Subject: Re: networkmanager hostname woes
Date: Wed, 13 Sep 2017 17:47:43 +0200

>> AFAIU, the cause is that networkmanager changes my hostname (after
>> DHCP?), in my case to “new-host2” or something similar, and this
>> seems to break the X session.  When I manually restore the hostname
>> with “sudo hostname <original-hostname>”, the problem is solved.  
>> Is
>> there anyway to disable this behaviour for networkmanager?
> [...]
> This makes me think that it might be a network configuration
> derived issue — but I have not been able to get to the bottom of 
> this
> yet…
>
> I see that you might be based in Belgium — I am too, and my home 
> network
> uses most of the defaults from Proximus' B-Box 2.  If this is the 
> case
> for you too, then perhaps it is a matter of the default settings in 
> that
> router?

Yes, I'm using the same router, and I can agree it's not 
“professional”-grade :-).  Still, I don't think a bad router 
configuration should be able to change my hostname.

Following Christopher Baines' suggestion, I created /etc/hostname by 
adding the following to my system configuration:

(define etc-hostname-service-type
   (service-type (name 'etc-hostname)
                 (extensions
                  (list (service-extension etc-service-type
                                           (lambda (hostname)
                                             (list `("hostname" 
,(plain-file "hostname" hostname)))))))))

and in the (operating-system (services ...)) list:

     (service etc-hostname-service-type host-name)

I don't know if this kind of extension should be added to an existing 
service (networkmanager itself, perhaps?).  Though I have the feeling 
a more proper solution should exist.

 From what I've read, it might also be a DHCP issue: some DHCP 
 clients are configured to take on the hostname offered by the 
 router, perhaps that could/should be changed?  I see that wicd has 
 its own settings for these things (/etc/wicd/wireless-settings.conf 
 contains things like usedhcphostname = 0).  I'm hoping someone with 
 more experience can give some advice here :)

Thomas

Re: networkmanager hostname woes

[Ludovic Courtès]

Hi Thomas,

Thomas Danckaert <thomas.danckaert@aeronomie.be> skribis:

> AFAIU, the cause is that networkmanager changes my hostname

I’ve never experienced this (even though I don’t have /etc/hostname),
but that looks like a serious bug we should fix.  Why would NM fiddle
with the host name?

I see that NM implements a “SetHostname” D-Bus RPC, and ‘nmtui’ has a
menu item to change the host name.

In NM, the ‘update_system_hostname’ function has this comment:

	/* Hostname precedence order:
	 *
	 * 1) a configured hostname (from settings)
	 * 2) automatic hostname from the default device's config (DHCP, VPN, etc)
	 * 3) the last hostname set outside NM
	 * 4) reverse-DNS of the best device's IPv4 address
	 *
	 */

Then nm-settings.c has code to deal with host names in all sort of
unpredictable ways.  To give you an idea:

--8<---------------cut here---------------start------------->8---
#define HOSTNAME_FILE_DEFAULT        "/etc/hostname"
#define HOSTNAME_FILE_UCASE_HOSTNAME "/etc/HOSTNAME"
#define HOSTNAME_FILE_GENTOO         "/etc/conf.d/hostname"

[...]

#if defined(HOSTNAME_PERSIST_SUSE)
#define HOSTNAME_FILE           HOSTNAME_FILE_UCASE_HOSTNAME
#elif defined(HOSTNAME_PERSIST_SLACKWARE)
#define HOSTNAME_FILE           HOSTNAME_FILE_UCASE_HOSTNAME
#elif defined(HOSTNAME_PERSIST_GENTOO)
#define HOSTNAME_FILE           HOSTNAME_FILE_GENTOO
#else
#define HOSTNAME_FILE           HOSTNAME_FILE_DEFAULT
#endif

[...]

static gchar *
read_hostname_gentoo (const char *path)
--8<---------------cut here---------------end--------------->8---

So, like Chris wrote, it honors /etc/hostname or /etc/HoSTNaM3 depending
on the phase of the moon.

I don’t understand the logic in there, but a quick fix would be to have
‘network-manager-service-type’ create /etc/hostname.

What do people think?

Ludo’.

Re: networkmanager hostname woes

[Thomas Danckaert]

From: ludo@gnu.org (Ludovic Courtès)
Subject: Re: networkmanager hostname woes
Date: Thu, 14 Sep 2017 10:17:08 +0200

> I don’t understand the logic in there, but a quick fix would be to have
> ‘network-manager-service-type’ create /etc/hostname.
> 
> What do people think?

I agree.  What is the best way to do that?

 - make network-manager-service extend etc-service?  I think in this
   case we'd need to pass the host-name to
   network-manager-service-type somehow?  It feels strange to make the
   system config's host-name a configuration parameter of
   network-manager-service-type just for this reason.

 - Create /etc/hosts in network-manager activation, using the result
   of ‘hostname’ at that point?

 - ...?

Thomas

Re: networkmanager hostname woes

[ng0]

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Arun Isaac transcribed 0.8K bytes:
> 
> Thomas Danckaert writes:
> 
> > Hi Guix,
> >
> > since the change to networkmanager, I've been running into the 
> > following problem: when I connect to a wireless network using 
> > networkmanager, I can no longer start graphical applications 
> > (starting any program fails with “cannot open display :0.0” and 
> > similar messages).
> >
> > AFAIU, the cause is that networkmanager changes my hostname (after 
> > DHCP?), in my case to “new-host2” or something similar, and this 
> > seems to break the X session.  When I manually restore the hostname 
> > with “sudo hostname <original-hostname>”, the problem is solved.  Is 
> > there anyway to disable this behaviour for networkmanager?
> 
> I have the exact same problem too. If somebody has a solution, I'd like
> to hear about it.

I don't understand your problem. This is public documented behavior of
NM.
Assuming that we build networkmanager with dhclient option/configure:

add to /etc/dhcp/dhclient.conf:

send host-name "yourhostname";


This always worked for me on Gentoo.
-- 
ng0
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Re: networkmanager hostname woes

[ng0]

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ng0 transcribed 2.3K bytes:
> Arun Isaac transcribed 0.8K bytes:
> > 
> > Thomas Danckaert writes:
> > 
> > > Hi Guix,
> > >
> > > since the change to networkmanager, I've been running into the 
> > > following problem: when I connect to a wireless network using 
> > > networkmanager, I can no longer start graphical applications 
> > > (starting any program fails with “cannot open display :0.0” and 
> > > similar messages).
> > >
> > > AFAIU, the cause is that networkmanager changes my hostname (after 
> > > DHCP?), in my case to “new-host2” or something similar, and this 
> > > seems to break the X session.  When I manually restore the hostname 
> > > with “sudo hostname <original-hostname>”, the problem is solved.  Is 
> > > there anyway to disable this behaviour for networkmanager?
> > 
> > I have the exact same problem too. If somebody has a solution, I'd like
> > to hear about it.
> 
> I don't understand your problem. This is public documented behavior of
> NM.
> Assuming that we build networkmanager with dhclient option/configure:
> 
> add to /etc/dhcp/dhclient.conf:
> 
> send host-name "yourhostname";
> 
> 
> This always worked for me on Gentoo.

I read the full thread again, our problem might be different
but providing this file might be a fix which could work.
-- 
ng0
GnuPG: A88C8ADD129828D7EAC02E52E22F9BBFEE348588
GnuPG: https://krosos.org/dist/keys/
https://www.infotropique.org https://www.krosos.org

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Re: networkmanager hostname woes

[Ludovic Courtès]

Thomas Danckaert <post@thomasdanckaert.be> skribis:

> From: ludo@gnu.org (Ludovic Courtès)
> Subject: Re: networkmanager hostname woes
> Date: Thu, 14 Sep 2017 10:17:08 +0200
>
>> I don’t understand the logic in there, but a quick fix would be to have
>> ‘network-manager-service-type’ create /etc/hostname.
>> 
>> What do people think?
>
> I agree.  What is the best way to do that?
>
>  - make network-manager-service extend etc-service?  I think in this
>    case we'd need to pass the host-name to
>    network-manager-service-type somehow?  It feels strange to make the
>    system config's host-name a configuration parameter of
>    network-manager-service-type just for this reason.
>
>  - Create /etc/hosts in network-manager activation, using the result
>    of ‘hostname’ at that point?
>
>  - ...?

Hmm, good points.  Maybe just create /etc/hostname unconditionally from
‘essential-services’?  It can’t hurt, right?

Ludo’.

Re: networkmanager hostname woes

[Thomas Danckaert]

From: ng0 <ng0@infotropique.org>
Subject: Re: networkmanager hostname woes
Date: Fri, 15 Sep 2017 12:14:49 +0000

> Arun Isaac transcribed 0.8K bytes:
>>
>> Thomas Danckaert writes:
>>
>> > AFAIU, the cause is that networkmanager changes my hostname 
>> (after
>> > DHCP?), in my case to “new-host2” or something similar, and this
>> > seems to break the X session.  When I manually restore the 
>> hostname
>> > with “sudo hostname <original-hostname>”, the problem is solved. 
>>  Is
>> > there anyway to disable this behaviour for networkmanager?
>>
>> I have the exact same problem too. If somebody has a solution, I'd 
>> like
>> to hear about it.
>
> I don't understand your problem.

The problem is that changing the hostname after starting an X 
session, breaks that session.

> This is public documented behavior of NM.

Can you point me to the networkmanager documentation?  Could help to 
find a proper way to configure this (adding some configuration 
options to our networkmanager service perhaps).  I couldn't 
immediately find anything helpful.

> Assuming that we build networkmanager with dhclient 
> option/configure:

seems like we do: the networkmanager package in in 
gnu/packages/gnome.scm has an option  (string-append 
"--with-dhclient=" dhclient)))

> add to /etc/dhcp/dhclient.conf:
>
> send host-name "yourhostname";

I think some people prefer not to send their own hostname to any 
router they connect to (assuming that's what “send host-name” does 
:-) ).  Do you think creating /etc/hostname instead is not a good 
solution?

Thanks!

Thomas

Re: networkmanager hostname woes

[ng0]

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Thomas Danckaert transcribed 2.2K bytes:
> From: ng0 <ng0@infotropique.org>
> Subject: Re: networkmanager hostname woes
> Date: Fri, 15 Sep 2017 12:14:49 +0000
> 
> > Arun Isaac transcribed 0.8K bytes:
> > > 
> > > Thomas Danckaert writes:
> > > 
> > > > AFAIU, the cause is that networkmanager changes my hostname (after
> > > > DHCP?), in my case to “new-host2” or something similar, and this
> > > > seems to break the X session.  When I manually restore the
> > > hostname
> > > > with “sudo hostname <original-hostname>”, the problem is solved.
> > > Is
> > > > there anyway to disable this behaviour for networkmanager?
> > > 
> > > I have the exact same problem too. If somebody has a solution, I'd
> > > like
> > > to hear about it.
> > 
> > I don't understand your problem.
> 
> The problem is that changing the hostname after starting an X session,
> breaks that session.
> 
> > This is public documented behavior of NM.
> 
> Can you point me to the networkmanager documentation?

Not documented as in documentation, but that this is known by
other systems. I've never read the documentation of NM in all
the years I've known this.

> Could help to find a
> proper way to configure this (adding some configuration options to our
> networkmanager service perhaps).  I couldn't immediately find anything
> helpful.
> 
> > Assuming that we build networkmanager with dhclient option/configure:
> 
> seems like we do: the networkmanager package in in gnu/packages/gnome.scm
> has an option  (string-append "--with-dhclient=" dhclient)))
> 
> > add to /etc/dhcp/dhclient.conf:
> > 
> > send host-name "yourhostname";
> 
> I think some people prefer not to send their own hostname to any router they
> connect to (assuming that's what “send host-name” does :-) ).  Do you think
> creating /etc/hostname instead is not a good solution?
> 
> Thanks!
> 
> Thomas

I don't have any opinion or further help, I just shared what I know
hoping that it could maybe help with further decisions.

How is not sharing your hostname with any router you connect to
a privacy option?
Assuming you don't share it with your local router, looking just
at email it still ends up (in the default case, if not set to forget
on the server) with computers inbetween you, me and gnu.org and
everyone and their email servers. You just have to be aware that the
net is insecure and broken.
Of course we can have a default hostname.
And if /etc/hostname helps to solve the initial problem, go for it.
-- 
ng0
GnuPG: A88C8ADD129828D7EAC02E52E22F9BBFEE348588
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Re: networkmanager hostname woes

[Thomas Danckaert]

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From: ludo@gnu.org (Ludovic Courtès)
Subject: Re: networkmanager hostname woes
Date: Fri, 15 Sep 2017 22:34:44 +0200

> Thomas Danckaert <post@thomasdanckaert.be> skribis:
>
>> From: ludo@gnu.org (Ludovic Courtès)
>> Subject: Re: networkmanager hostname woes
>> Date: Thu, 14 Sep 2017 10:17:08 +0200
>>
>>> I don’t understand the logic in there, but a quick fix would be 
>>> to have
>>> ‘network-manager-service-type’ create /etc/hostname.
>>>
>>> What do people think?
>>
>> I agree.  What is the best way to do that?
>>
>>  - make network-manager-service extend etc-service?  I think in 
>> this
>>    case we'd need to pass the host-name to
>>    network-manager-service-type somehow?  It feels strange to make 
>> the
>>    system config's host-name a configuration parameter of
>>    network-manager-service-type just for this reason.
>>
>>  - Create /etc/hosts in network-manager activation, using the 
>> result
>>    of ‘hostname’ at that point?
>>
>>  - ...?
>
> Hmm, good points.  Maybe just create /etc/hostname unconditionally 
> from
> ‘essential-services’?  It can’t hurt, right?

I don't think so, only for people committed to extreme minimalism.  
The attached patch fixes the issue on my system.  Will it do?

Thomas

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From 76a461ff1540807d8beb98c298a8ea0165a6aaa4 Mon Sep 17 00:00:00 2001
From: Thomas Danckaert <thomas.danckaert@gmail.com>
Date: Sat, 16 Sep 2017 13:54:40 +0200
Subject: [PATCH] system: Create "/etc/hostname".

* gnu/system.scm (operating-system-etc-service): Add a plain-file with the
  operating-system-host-name.
---
 gnu/system.scm | 1 +
 1 file changed, 1 insertion(+)

diff --git a/gnu/system.scm b/gnu/system.scm
index bb7e8531e..2ad4b3054 100644
--- a/gnu/system.scm
+++ b/gnu/system.scm
@@ -642,6 +642,7 @@ fi\n")))
        ("bashrc" ,#~#$bashrc)
        ("hosts" ,#~#$(or (operating-system-hosts-file os)
                          (default-/etc/hosts (operating-system-host-name os))))
+       ("hostname" ,(plain-file "hostname" (operating-system-host-name os)))
        ("localtime" ,(file-append tzdata "/share/zoneinfo/"
                                   (operating-system-timezone os)))
        ("sudoers" ,(operating-system-sudoers-file os))))))
-- 
2.14.1

Re: networkmanager hostname woes

[Ludovic Courtès]

Hi Thomas!

Thomas Danckaert <post@thomasdanckaert.be> skribis:

> From: ludo@gnu.org (Ludovic Courtès)
> Subject: Re: networkmanager hostname woes
> Date: Fri, 15 Sep 2017 22:34:44 +0200

[...]

>> Hmm, good points.  Maybe just create /etc/hostname unconditionally
>> from
>> ‘essential-services’?  It can’t hurt, right?
>
> I don't think so, only for people committed to extreme minimalism.
> The attached patch fixes the issue on my system.  Will it do?
>
> Thomas
>
> From 76a461ff1540807d8beb98c298a8ea0165a6aaa4 Mon Sep 17 00:00:00 2001
> From: Thomas Danckaert <thomas.danckaert@gmail.com>
> Date: Sat, 16 Sep 2017 13:54:40 +0200
> Subject: [PATCH] system: Create "/etc/hostname".
>
> * gnu/system.scm (operating-system-etc-service): Add a plain-file with the
>   operating-system-host-name.
> ---
>  gnu/system.scm | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/gnu/system.scm b/gnu/system.scm
> index bb7e8531e..2ad4b3054 100644
> --- a/gnu/system.scm
> +++ b/gnu/system.scm
> @@ -642,6 +642,7 @@ fi\n")))
>         ("bashrc" ,#~#$bashrc)
>         ("hosts" ,#~#$(or (operating-system-hosts-file os)
>                           (default-/etc/hosts (operating-system-host-name os))))
> +       ("hostname" ,(plain-file "hostname" (operating-system-host-name os)))

LGTM.  Maybe just add a comment pointing to this discussion, so we know
why this file matters.

Thank you!

Ludo’.