dhclient and dhcp update require restart?

[Dariusz J. Garbowski]

On 09/02/2009 02:33 PM, David Cantrell wrote:
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> On Wed, 2 Sep 2009, Dennis J. wrote:
>
>> On 08/27/2009 07:49 PM, David Cantrell wrote:
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>>> On Wed, 26 Aug 2009, Dariusz J. Garbowski wrote:
>>>
>>>> Hi, something that bothers me a bit... More and more system restart
>>>> requests with each update (even if one doesn't use the package at the
>>>> time).
>>>>
>>>> Is this necessary for dhclient and dhcp update packages to require
>>>> restart?
>>>> Wouldn't "service network restart" and "service dhcpd restart" in the
>>>> install/upgrade
>>>> scripts do the trick (after checking that the service is actually
>>>> running)?
>>>> Ssh used to do that since, well, as far as I remember.
>>>
>>> Yes, 'service dhcpd restart' will work fine for dhcpd. For dhclient, 
>>> it's
>>> not necessarily as simple as restarting the network service. If you are
>>> using
>>> the network service, that will work fine. If you are using 
>>> NetworkManager,
>>> you'll need to either restart NetworkManager or have it down the 
>>> connection
>>> you're using dhclient on and bring it back up.
>>
>> Why is a restart of NetworkManager necessary in this case? If 
>> dhclient reinitializes the interface and gets the old dhcp data then 
>> nothing really changes and NetworkManager shouldn't have to care. If 
>> e.g. der IP changes then NetworkManager should detect that and 
>> reinitialize the connection info on its end (after all the "new" 
>> interface might not be connected to anything and thus have to be 
>> marked as down anyway).
>
> It doesn't work that way.  dhclient isn't a service with an init.d 
> script.  If
> you are using NetworkManager, dhclient is a child process of 
> NetworkManager.
> You can't just restart dhclient since NetworkManager is controlling 
> it.  You
> have to either tell NetworkManager to down the interface, stop 
> dhclient, and
> bring it back up -- or restart NetworkManager.  Either way, the result 
> is the
> same.
>
> If you are using the network service, dhclient is run when the 
> interface is
> ifup'ed (so either restart the network service or ifup/ifdown the 
> interface in
> that case).

Yeah, dhclient works even if you don't use NetworkManager (I don't). So 
ifup/ifdown is necessary, which may or not be a good idea if something 
else running on the system relies on e.g. files open on NFS/SMB.

Yet, can something similar to sshd be done to dhcpd?

-- 
thufor




>
> - -- David Cantrell <dcantrell at redhat.com>
> Red Hat / Honolulu, HI
>
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