[Bug 837385] [NEW] hostname from dhcp STILL not set, despite multiple ubuntu fixes and bug reports

[perpetualrabbit]

Public bug reported:

Despite multiple bug reports and attempts at fixes, ubuntu versions
maverick and natty do NOT set their hostname from dhcp. See: #537978,
#482313, #90388, #476491

Releases: 
---------------
   maverick: lsb_release -rd
        Description:	Ubuntu 10.10
        Release:	10.10
   natty: lsb_release -rd
        Description:     Ubuntu 11.04
        Release:  11.04

Versions of dhcp and hostname packages:
-------------------------------------------------------------------
    maverick:dpkg -l | grep -E dhcp\|hostname
       ii  dhcp3-client                    3.1.3-2ubuntu6.3                                  DHCP client
       ii  dhcp3-common                    3.1.3-2ubuntu6.3                                  common files used by all the dhcp3* packages
       ii  hostname                        3.04ubuntu1                                       utility to set/show the host name or domain name

    natty: dpkg -l | grep -E dhcp\|hostname
       ii  hostname                                 3.05ubuntu1                                utility to set/show the host name or domain name
       ii  isc-dhcp-client                          4.1.1-P1-15ubuntu9.1                       ISC DHCP client
       ii  isc-dhcp-common                          4.1.1-P1-15ubuntu9.1                       common files used by all the isc-dhcp* packages

What I expect to happen:
---------------------------------------
     With client configured with empty /etc/hostname, and main network interface configured for dhcp, I expect the hostname to be set during boot.

What happened instead:
---------------------------------------
    With empty /etc/hostname, the machine comes up with (none) as hostname, with /etc/hostname missing entirily, the hostname is set to `localhost´

Elaboration:
-------------------
In networks with lots (dozens or hundreds) of linux workstations I keep the /etc/hostname on each of them empty. They get the hostname from dhcp at boot-time and set it. Managing lots of clients or a HPC cluster becomes impractical if I have to set all hostnames on them by hand. Installation in such a situation typically happens from an imaging host, where one or maybe a few images is used to install on hundreds of clients.
So there must be NO host-specific configuration in these images. Hostnames are set by the dhcp client with information provided by the dhcp server. UUID's are NOT used in /etc/fstab, /boot/grub/grub.cfg, /etc/grub.d/*, or within the initrd.img file. Instead device files are used: /dev/sda for instance. The kernel commandline
root=UUID=db662660-94f7-4e94-8ed4-785fa9938ad0 ro quiet may be correct for the _image_ but not for the client it is copied to! Yes, I could figure out with blkid and script it so that the UUID for the client will be correct in various places, but that is not what I want, it is too error-prone.

I want to be able to configure in /etc/default/dhclient that I want to
set the hostname as provided by the dhcp server, and in
/etc/default/grub that I want to use device files, not UUIDs.

Unfortunately Canonical gives me no such configuration options at this
time, and this is not good for sysadmins like me who need tools to
administrate lots of workstations.

Also note that dhcp clients can push a client side provided hostname to
a dhcp or dns server, which is useful if you have a laptop that the user
has root-access to. My situation is the other way around: the users have
NO root-access on the workstations or the HPC cluster, and hostnames are
centrally pushed to the clients.

For this latest dhcp host-setting regression I suspect two reasons.
I suspect two reasons:
    1) upstart sets the hostname in recent ubuntu distros, and it simply  does:
        exec hostname -b -F /etc/hostname
        This will not work if /etc/hostname is empty!
    2) dhclient does not set the hostname despite being so configured in /etc/dhcp3/dhclient.conf
        Apparantly it is possible to write an exit hook script that sets the hostname like this:
# ===== /etc/dhcp/dhclient-exit-hooks.d/hostname ======
if [[ -n $new_host_name ]]
then
    echo "$new_host_name" > /etc/hostname
    /bin/hostname $new_host_name
fi

Apparantly $new_host_name is the internal variable that dhclient uses for the hostname info that it got from the dhcp server.
 
The correctly configured dhcp server has stanzas for the clients like this:

  host maris007 {
    fixed-address 10.0.0.7;
    hardware ethernet 00:30:48:58:df:14;
    option host-name "maris007";}

** Affects: dhcp3 (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/837385

Title:
  hostname from dhcp STILL not set, despite multiple ubuntu fixes and
  bug reports

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