Cannot set Device name (hostname) under Details section in System Settings on 12.04

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Thank you for your bug report, I think it has been reported before but I don't find it now, but a summary:
- changing hostname is not something user frequently do
- it can create issue, especially for the running session (that breaks xorg authentification tokens)
- the g-c-c interface required hostnamed from systemd which we don't use

I'd also like to see this fixed. It is occasionally required, and is one of the issues that makes Ubuntu seem less complete and mature. I assume that the only way to do it at the moment is to edit /etc/hostname and /etc/hosts. Anyone know otherwise? Also, I've seen rumours of minor issues when this is done (can't remember exactly but someone said they saw theold hostname hanging about somewhere). Anyone aware of anything else which needs changing?

As I recall, this is possible when booting from a live CD (or USB). Why is it possible when booting live but not otherwise?

That should be all you need to do Andy. You shouldn't have problems if you set those there unless you have a DNS server, in which case you should update those records too. Checks your /etc/nsswitch.conf file for the "hosts" line and check it has "files" and "dns" in that order, then your machine will use its /etc/hosts file before looking it up using DNS.

This bug was fixed in the package gnome-control-center - 1:3.6.3-0ubuntu20

---------------
gnome-control-center (1:3.6.3-0ubuntu20) raring; urgency=low

  * debian/gnome-control-center.pkla, gnome-control-center-data.install:
    - Install a .pkla to allow admins to set the hostname. This can be dropped
      when Ubuntu includes policykit >=0.106 since gnome-control-center
      ships the updated rules already (LP: #962369)
  * debian/control.in:
    - Recommend libnss-myhostname (LP: #1162475, #1162478)
  * debian/patches/62_update_translations_template.patch: Refreshed
 -- Jeremy Bicha <email address hidden> Wed, 10 Apr 2013 16:15:36 -0400

Re-opening this bug since bug 1162478 was rejected for fixing for Ubuntu 13.04 so this fix was also reverted because it was incomplete.

Appending the content of Bug #1190048 here, ignore me if its not useful
1. I expected there's a pre-installed GUI utility in Ubuntu to change hostname.
2. I expected it appears in GNOME Control Center(a.k.a. System Settings) -> Details -> "Device name" textbox
    * In fact there's really a "textbox" at the location but is not editable and there's no "Unlock" button at that view.
3. I expected if I run GNOME Control Center as root (gksudo gnome-control-center) I can change my hostname
    * In fact when GNOME Control Center run as root, the "textbox" really turn's into editable, but edit the content still won't apply to the system temporarily nor permanently.
4. I supposed there's many user having the same conclusion like me, so please help ;)

This is working in Ubuntu GNOME 16.04 LTS