NFS help

[Greg Julius]

> On 8/27/05, brad.mugleston at comcast.net <brad.mugleston at comcast.net> wrote:
> > I don't follow what your saying - I'm trying to set up an NFS
> > system using DHPC - it sounds like your suggesting I use DHCP
> > (which I am) but how do I set up my /etc/fstab to mount the files
> > on different machines using hostnames with IP's that can change
> > under DHCP?
> 
> Brad,
> 
> I think you are misunderstanding me. I understood that you wanted to
> use DHCP for the machine you are using as an NFS server and I
> suggested having the DHCP server assign your NFS server a fixed
> address based on its MAC.
> 
> In dhcp.conf you would have something like the following to do that ...
> 
> host nfs-1 {
>   hardware ethernet XX:XX:XX:XX:XX:XX;
>>   fixed-address YYY.YYY.YYY.YYY;
>> }
>> 
>> where XX:XX:XX:XX:XX:XX is the MAC address of your NFS server and
>> YYY.YYY.YYY.YYY is the IP you want to always assign to it.
>> 
>> You can then have your DNS server get updates from your DHCP server or
>> you can just set up your DNS server to resolve the name and IP
>> correctly.
>> 
>> Either way, if you aren't running your own DNS and DHCP servers, then
>> perhaps this isn't what you really want to do.
>> 
>> I think you are going to just have problems if the IP of your NFS
>> server keeps changing. I don't know how to configure /etc/fstab to
>> accommodate that. It expects an IP or a name that resolves to the
>> correct IP. But you can configure DHCP to not change the IP of your
>> NFS server. That is what I was suggesting.
>> 
>> John
>> 
>This may sound a little callous, but the first thing I think you should do
>is read up on NFS, DNS, DHCP.

Yeah, callous was probably the correct word.  But you are right, boning up
on 
these facilities is the thing to do.

In support of Brad, however, sometimes a bit of plain old-fashioned help 
navigating the waters is pricelss.

>Cause you are trying to do something you have
>no idea how to do.  The reason I am saying this is that you need to know
how
>a name is resolved in order to see how to mount the resource.  Tha
>assignment of the IP is irrelevant to what you are doing, what you should
be
>worried about is how everyone resolves the name you assign the resource and
>that will be done thru the DNS.  So if everyone is looking for resource A
>then when DHCP assigns a IP to resource A and that resource is reported to
>the DMS server then everyone can mount the resource cause they know who and
>what it is cause the DNS is going to report its current ip address and if
it
>changes it will report the new one so everyone will always be happy.  So
>forget the assignment of a fixed IP and worry about resolving the name with
>the DNS.  Hopefully you will go out on the net and search for the facts you
>need and see what you need to do.  It might make it easier in your mind to
>assign a fixed IP but it in no way a necessary requirement for what you are
>wanting to do.  Good Luck!!!!!!!!!1

Brad, As I understand it, you want to be able to use a name in the NFS
mount.

A name is a good thing for it's value as a handle.  It's much the same
reason
we use domain names instead of IP quads to navigate the web.  Names are just
easier and if necessary the underlying address can change without everyone
having to update their URLs.

Having said that, the point was made that having the IP address dance around
would not be a terribly good idea.

One of the replies was to the point you can prevent the IP from changing 
until you want it to by using some DHCP parameters to have DHCP reserve the
desired IP for that server's use by keying on the MAC address.  However,
unless the DNS has the same IP address assignment, nothing else is going to
know what that IP is.

To do what you want to do, that is give a name to a device/server/host that
is centrally managed (meaning you don't want to update every hosts file on
your network), then you need to have both DHCP and DNS running on your
network.  And you must be able to administer them.  I strongly suggest that
DNS and DHCP services DO run on the same server.  At a minimum, your DHCP
server is going to require an assigned (by you) IP address.

You can set up DHCP to update the DNS - called Dynamic DNS (DDNS) - when IP
assignments are made.  OR, more simply, you can just have DHCP 'stick' the
address based upon the MAC address and at the same time manually update your
DNS to associate the name with the same IP.  After all, you are
administering
both of them.  That makes it just two places to update should you want to
change the address.

This latter is the first thing I would do.  Break your training project into
pieces.  1) Make sure the NFS stuff is working by using an IP you have in
mind.  2) Set up DHCP to 'stick' the IP to the desired machine by the MAC
address.  3) Update the DNS by manually assigning the name to the IP.  
4) Make sure you can reach the machine by name (use ping for example).
5) Change the NFS mount to use the Name and make sure it works that way.
6) If you are still up to it, then play with getting DHCP to update the DNS.

I hope that's useful to you.  There is some good material out on the web
for setting up stuff such as this.  I've had good luck getting assistance
from the folks who frequent this list.

Blessings,
-g