Changing hostname disturbs the system and DE’s like KDE, Gnome, etc… What can I do to allow it anyway

hostnamekde

Long time ago I started to develop some kind of stealthmode-demon in c++.
Part of this is to be only run as root and another part of it is, to change the hostname to a randomn generated one.
I experienced, that any change to my hostname ( either via virtual terminal or via my stealthdemon or via a dhcp-feature ) somehow disturbs the system.
One example is, that suddenly all KDE-apps cannot start, neither by shortcut nor by click. If I reset my hostname to the original one, then all seems to work perfect.

My questions are:

What else is invoked, when issuing hostname via bash ?
What else is invoked, when issuing hostname in a c/c++ code ?
What is the reason for the strange behaviour? ( Although I guess,
it can be,that either xorg or kde itself was somehow linked to the old
hostname, but after the change they are not linked anymore )
What can be done, to keep the system stable but still allowing
to change a hostname , either by shell or by code ?

Thx in advance.

Best Answer

X auth file (~/.Xauthority, /tmp/xauth-*, etc.) contains the system hostname. If it differs from the actual hostname (as shown by hostname(1)), an X application won’t start.

In my case, it prints “No protocol specified Could not connect to display :0”. But changing hostname in the X auth file to the actual value fixes the problem. (I used a hex editor to test that; well, there should be a better way to change it)

Related Solutions

Linux – Can we switch desktop ( GNOME, KDE, etc ) within linux

Yes you can, for example you can run following command for installing KDE desktop:

sudo apt-get install kde-standard

Or for full set of package/applications (it may take a lot of tim) you can run:

sudo apt-get install kde-full

after next login select KDE from "session" on the Login Prompt to start enjoying the Kool Desktop Environment (KDE).

I recommend if you want to try new desktop, install a fresh one of an specific derivative (e.g. Kubuntu or Mint KDE).

The difference between hostname, hostname –fqdn, and hostname -A

hostname returns the configured hostname or nodename. In practice, it can either be a short name (in most configurations) or a long name (normally the FQDN in this case). The short name is given by hostname --short.

hostname --fqdn returns the FQDN, which is gethostbyname on the nodename (as returned by the uname system call, see uname(2) man page).

hostname -A is something obscure and non-intuitive. In particular, despite its name and description ("all FQDNs"), it doesn't give the standard FQDN, by design. Thus I would say: do not use it. One reason is that it misses valid IP addresses of the machine, such as 127.0.1.1, with which the FQDN may be associated in the /etc/hosts file (this is currently the default under Debian and Ubuntu, for instance). Another issue with the hostname -A method is that the reverse resolution of an IP address doesn't necessarily give a FQDN; it can just be a short name.

Concerning your problem with python, it may be a bug there. I don't know. I suggest that you try the following Perl script:

#!/usr/bin/env perl

use strict;
use POSIX;

my $nodename = (POSIX::uname)[1];
print "Nodename: $nodename\n";

my @ghbn = gethostbyname $nodename;
print "FQDN: $ghbn[0]\n";

$ghbn[0] !~ /\./ && $ghbn[1] =~ /(\S+\.\S+)/
  and print "Fixed FQDN from aliases: $1\n";

Best Answer

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Linux – Can we switch desktop ( GNOME, KDE, etc ) within linux

The difference between hostname, hostname –fqdn, and hostname -A

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