"DHCP set the hostname"

host-name is optional, right?

I am sure I know the answer, but can't find support for it.

This is for a olpc bugreport that goes like this:

cjb: doesn't DHCP set the hostname, though?
CarlFK: it can, but from what I have seen dhcp doesn't
always happen
CarlFK: and it isn't guaranteed

cjb: if dhcp doesn't happen, we're not on a network and
don't care that we don't 
have a unique hostname.

Carl K

A read of the manual page for dhcp-option(5) and
dhclient-script(5) is 
useful.  An excerpt from the man page says:
       option host-name string;

          This option specifies the name of the client.  The
name may  
or  may
          not be qualified with the local domain name (it is
preferable 
to use
          the domain-name option to specify the domain
name).   See  
RFC  1035
          for  character  set  restrictions.   This  option
is only 
honored by
          dhclient-script(8) if the hostname for the  client
 machine  
is  not
          set.

The use of the host-name specified is optional and depends
upon how the 
client is configured.  Now the next logical question, is how
does this 
work in Winderz?


Carl Karsten wrote:
> host-name is optional, right?
>
> I am sure I know the answer, but can't find support for
it.
>
> This is for a olpc bugreport that goes like this:
>
> cjb: doesn't DHCP set the hostname, though?
> CarlFK: it can, but from what I have seen dhcp doesn't
always happen
> CarlFK: and it isn't guaranteed
>
> cjb: if dhcp doesn't happen, we're not on a network and
don't care that we don't 
> have a unique hostname.
>
> Carl K
>   

Thanks.  Not quite as definitive as I had hoped for, but
good enough.

Next Q: what are the implications of multiple machines with
the same hostname? 
In other words: does it matter if they are all left set to
localhost.localdomain?

Carl K

Tim Peiffer wrote:
> A read of the manual page for dhcp-option(5) and
dhclient-script(5) is 
> useful.  An excerpt from the man page says:
>        option host-name string;
> 
>           This option specifies the name of the client.
 The name may  
> or  may
>           not be qualified with the local domain name
(it is preferable 
> to use
>           the domain-name option to specify the domain
name).   See  
> RFC  1035
>           for  character  set  restrictions.   This 
option is only 
> honored by
>           dhclient-script(8) if the hostname for the 
client  machine  
> is  not
>           set.
> 
> The use of the host-name specified is optional and
depends upon how the 
> client is configured.  Now the next logical question,
is how does this 
> work in Winderz?
> 
> 
> Carl Karsten wrote:
>> host-name is optional, right?
>>
>> I am sure I know the answer, but can't find support
for it.
>>
>> This is for a olpc bugreport that goes like this:
>>
>> cjb: doesn't DHCP set the hostname, though?
>> CarlFK: it can, but from what I have seen dhcp
doesn't always happen
>> CarlFK: and it isn't guaranteed
>>
>> cjb: if dhcp doesn't happen, we're not on a network
and don't care that we don't 
>> have a unique hostname.
>>
>> Carl K
>>   
> 
> 
> 

Carl Karsten wrote:

>Next Q: what are the implications of multiple machines
with the same hostname?
>In other words: does it matter if they are all left set
to 
>localhost.localdomain?

A: It depends !


If the client is not providing any service used by another
system 
then I would expect there to be little problem. However,
most clients 
now do things like file sharing, zeroconf (aka Rendevous),
register 
with servers etc and so it does become important - though I
assume 
zeroconf must have a mechanism for dealing with this.

It matters only in 2 cases.  In the netbios context, a
duplicate name is 
as bad as a duplicate IP address.  In the DHCP informs
Dynamic DNS, I 
think that only the last update will win the duplicate name
issue.  In 
the long run, if a name doesn't leak out of the box, then
the name is 
private..  think RFC1918 private IP space. If there is
multiple use of 
an IP, it is ok as long as the address is not leaked into
the public space.

With use of DDNS and the large predominance of the use of
SRV records to 
promote services, I can see the name leaking out fairly
easily albeit in 
error.  How many people really turn off services they don't
need, like 
file sharing, or print sharing?
I can see it easy on the LAN for situations to arise where
someone 
broadcasts for printer service resolution, and his neighbor
says sure..  
a printer is located at 'joes printer'localhost.localdomain.

I do have approximately 80,000 devices that are maintained
by people 
whose qualifications to do so span the spectrum.  That 
said, I have not 
really seen any of the above in the last 10 years.

Tim

Carl Karsten wrote:
> Thanks.  Not quite as definitive as I had hoped for,
but good enough.
>
> Next Q: what are the implications of multiple machines
with the same hostname? 
> In other words: does it matter if they are all left set
to localhost.localdomain?
>
> Carl K
>
> Tim Peiffer wrote:
>   
>> A read of the manual page for dhcp-option(5) and
dhclient-script(5) is 
>> useful.  An excerpt from the man page says:
>>        option host-name string;
>>
>>           This option specifies the name of the
client.  The name may  
>> or  may
>>           not be qualified with the local domain
name (it is preferable 
>> to use
>>           the domain-name option to specify the
domain name).   See  
>> RFC  1035
>>           for  character  set  restrictions.   This
 option is only 
>> honored by
>>           dhclient-script(8) if the hostname for
the  client  machine  
>> is  not
>>           set.
>>
>> The use of the host-name specified is optional and
depends upon how the 
>> client is configured.  Now the next logical
question, is how does this 
>> work in Winderz?
>>
>>
>> Carl Karsten wrote:
>>     
>>> host-name is optional, right?
>>>
>>> I am sure I know the answer, but can't find
support for it.
>>>
>>> This is for a olpc bugreport that goes like
this:
>>>
>>> cjb: doesn't DHCP set the hostname, though?
>>> CarlFK: it can, but from what I have seen dhcp
doesn't always happen
>>> CarlFK: and it isn't guaranteed
>>>
>>> cjb: if dhcp doesn't happen, we're not on a
network and don't care that we don't 
>>> have a unique hostname.
>>>
>>> Carl K
>>>   
>>>       
>>
>>