dhcp with /etc/network/interfaces

[David Henderson]

Just following up with this...

Thanks,
Dave


On 9/20/16, David Henderson <dhenderson at digital-pipe.com> wrote:
> Thanks for your help with this too Denys.  Answers are inline...
>
>
> On 9/20/16, Denys Vlasenko <vda.linux at googlemail.com> wrote:
>> On Tue, Sep 20, 2016 at 5:31 PM, David Henderson
>> <dhenderson at digital-pipe.com> wrote:
>>> Hey Martin, thanks again for your help!  So I had to bring back
>>> 'sneaker-net' to get strace on the machine via flash drive (after
>>> locating one), but it is now on the machine!  I could not see anything
>>> in the 'ps' output (and it is the GNU version) regarding what was
>>> being called for contacting a DHCP server for the adapter.  I also
>>> tried running the command that Peter suggested, but the command he
>>> listed has invalid syntax.
>>
>> An examlpe run works for me:
>>
>> $ strace -f -e execve sh -c /bin/pwd
>> execve("/usr/bin/sh", ["sh", "-c", "/bin/pwd"], [/* 52 vars */]) = 0
>> execve("/bin/pwd", ["/bin/pwd"], [/* 52 vars */]) = 0
>> /tmp
>> +++ exited with 0 +++
>>
>> You might have an old version of strace.
>
> Possibly, it chokes with the 'execve' parameter as it's not valid in
> my 'strace'.
>
>
>>> After a few more calls and a ton of goop
>>> from 'strace'
>>
>> We need the entire "ton of goop" from strace.
>> For example, the "strace -oLOG -f -tt -s99 COMMAND" is my favorite.
>>
>>
>>>, it appears that 'udhcpc' was being called as follows
>>> (at least on my dev machine):
>>>
>>> udhcpc -R -n -p /var/run/udhcpc.eth0.pid -i eth0
>>>
>>> (Just in case anyone else comes across this post)
>>>
>>> Now that I know what is being called, can anyone help with the other
>>> part of the original question?
>>
>> Ok, the question:
>>
>>> scripts that are run in the /etc/network/if-{,pre-,post-}{up,down}.d/
>>> directories.  Can/should I specify a script in the proper directory to
>>> execute the udhcpc binary (or another binary for that matter) with my
>>> own parameters for the interface without BB trying to use its own
>>> methods of obtaining an IP address automatically - effectively
>>> preventing the duplication of requests to the DHCP server for that
>>> interface?
>>
>> My personal opinion is that as soon as "simple" ifup/ifdown setup
>> is too primitive for your needs, e.g.:
>> - you need many IPs on one iface,
>> - you need dynamical ifaces (ppp, vpn), and you need to redefine
>>   routing/firewalling based on what's up and what isn't,
>> - you need additional things to be started/stopped
>>   (WPA supplicant, babysitter)
>>
>> at this point ifup becomes more PITA than help. It forces you
>> to do stuff in awkward ways.
>
> So can I perform my own methods via the scripts to prevent BB from
> attempting its own 'udhcpc' calls?  I don't want duplicate calls to
> the same DHCP server.
>
> Thanks,
> Dave
>