[Samba] Samba - Bind9 DNS - ISC-DHCP - obsolete DNS entries

Rowland Penny rpenny at samba.org
Wed Jan 2 11:51:54 UTC 2019

On Wed, 2 Jan 2019 12:16:47 +0100
Martin Krämer via samba <samba at lists.samba.org> wrote:

> Hi everyone,
> I have setup a Samba domain with BIND9 dns backend.
> Using ISC-DHCP-Server and procedure/script described in samba wiki I
> have configured dynamic dns updates.
> https://wiki.samba.org/index.php/Configure_DHCP_to_update_DNS_records_with_BIND9
> In my network I am using PXE to deploy new debian machines.
> Booting a nfsroot and then using chroot to install my new system, for
> each machine there are two dns entries
> "dhcp-<pxe>-<device>-<ip>-<address>" created,
> both having their own IP (I assume one for nfsroot and one for chroot
> environment).
> Furthermore during the setup process I change the hostname and use
> "dhclient -r && dhclient" to be able to resolve the hostname
> correctly. This is causing an additional dns entry for the correct
> hostname using the same IP as my chroot environment.
> After restarting my newly installed client this means I end up with
> three dns entries for the same machine, one correct and two incorrect.
> Even after a longer time schedule (I have waited up to 49 hours of the
> client being turned off) the wrong dns entries do not disappear.
> My question now is how can I make sure that the wrong dns entries are
> not created / get updated correctly / disappear after a short amount
> of time? I would like to end up with only one correct dns entry for
> one client (NIC).

This is something I never considered when I wrote the DHCP update
script (mainly because I do not use PXE), but it is a just a
bash script :-)

I think you will need to extend the script to check for the unwanted
dns entries and then delete them with nsupdate, failing this, use
another script to delete the unwanted entries at first boot.


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