Anonymous_User Absent Member.
Absent Member.
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Clustering and DNS/BIND Services

The templates for both the DNS and DHCP services that are created when
clustering services in installed includes a number of definitions and
commands pertaining to mounting file systems.

#!/bin/bash
.. /opt/novell/ncs/lib/ncsfuncs

# define the IP address
RESOURCE_IP=a.b.c.d
# define the file system type
MOUNT_FS=reiserfs
# define the device
MOUNT_DEV=/dev/evms/dhcp
# define the mount point
MOUNT_POINT=/mnt/dhcp

# mount the file system
exit_on_error mount -t $MOUNT_FS $MOUNT_DEV $MOUNT_POINT

# add the IP address
exit_on_error add_secondary_ipaddress $RESOURCE_IP

# start dhcpd
exit_on_error /usr/sbin/dhcpd -cf $MOUNT_POINT/etc/dhcpd.conf -lf
$MOUNT_POINT/var/lib/dhcp/dhcpd.leases

# return status
exit 0

Is this necessary? I've been able to run a DNS cluster resource by only
defining and adding the secondary IP address and starting the DNS service
(rcnamed start). Am I losing some functionality by not mounting an
associated file system?

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3 Replies
Anonymous_User Absent Member.
Absent Member.

Re: Clustering and DNS/BIND Services

Hi Sean,

Using a cluster volume for the DHCP resource is important as the lease
table needs to be kept between nodes. Otherwise you can end up with
duplicate IP addresses on the network.

DNS is not so important if you're running secondaries on the cluster
that point back to a zone master. The worst that will happen here is
that they will perform a zone transfer as soon as the resource is
brought online. TBH, i usualy dont even cluster DNS - i just leave it
running on all nodes at all times!

Now, if your cluster is a primary server for a DNS zone, you will need
to cluster it - records added on one server must be available on
another server, and a shared volume is much better than keeping the
config files in sync by hand!

HTH

Cheers,

Steve

On Tue, 12 Jun 2007 19:59:24 GMT, bdkmcgl@budget.state.ny.us (Sean)
wrote:

>The templates for both the DNS and DHCP services that are created when
>clustering services in installed includes a number of definitions and
>commands pertaining to mounting file systems.
>
>#!/bin/bash
> /opt/novell/ncs/lib/ncsfuncs
>
># define the IP address
>RESOURCE_IP=a.b.c.d
># define the file system type
>MOUNT_FS=reiserfs
># define the device
>MOUNT_DEV=/dev/evms/dhcp
># define the mount point
>MOUNT_POINT=/mnt/dhcp
>
># mount the file system
>exit_on_error mount -t $MOUNT_FS $MOUNT_DEV $MOUNT_POINT
>
># add the IP address
>exit_on_error add_secondary_ipaddress $RESOURCE_IP
>
># start dhcpd
>exit_on_error /usr/sbin/dhcpd -cf $MOUNT_POINT/etc/dhcpd.conf -lf
>$MOUNT_POINT/var/lib/dhcp/dhcpd.leases
>
># return status
>exit 0
>
>Is this necessary? I've been able to run a DNS cluster resource by only
>defining and adding the secondary IP address and starting the DNS service
>(rcnamed start). Am I losing some functionality by not mounting an
>associated file system?


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Anonymous_User Absent Member.
Absent Member.

Re: Clustering and DNS/BIND Services

Steve,

Thank you for taking the time to reply.

So if I correctly understand how this will work, I will need to create a
cluster enabled pool and associated volume on a shared disk system (fibre
channel SAN in our case). Should the server running DHCP (or DNS or any
other similar service) become unavailable, the pool and volume will then
be made available to another server in the cluster on which the DHCP
service will then run?

Thanks again.

Sean

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Anonymous_User Absent Member.
Absent Member.

Re: Clustering and DNS/BIND Services

> Now, if your cluster is a primary server for a DNS zone, you will need
> to cluster it - records added on one server must be available on
> another server, and a shared volume is much better than keeping the
> config files in sync by hand!


Then another question, if I may.

If the cluster is a primary, and we want two DNS servers running at all
times, would we then have a master and a slave, and then a failover for
the master and a failover for the slave?

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