NetworkManager

[Erik Christiansen]

On Wed, Oct 08, 2008 at 12:20:15PM -0300, Derek Broughton wrote:
> Erik Christiansen wrote:
> > On Tue, Oct 07, 2008 at 11:58:45AM -0300, Derek Broughton wrote:
> >> 
> >> LOL.  You didn't get a thing out of this thread, did you?  Network
> >> Manager NEVER writes to /etc/resolv.conf.
> > 
> > Derek, your advice is very frequently useful and generally more
> > knowledgeable than my efforts. However, it is a mistake to assume to be
> > omniscient.
> 
> Not omniscient, but I do understand how NM works.

In general, doubtless. But in this specific case, the accumulating
evidence must eventually result in expanded understanding replacing
certitude, I hope. 

> > It was only when network-manager was removed, that the file overwrites
> > ceased. Since it did the same on 2 or 3 reboots before I was
> > sufficiently annoyed to slit its throat, the crime was sufficiently
> > proven.
> 
> And when everytime the guard dog barks, you find something's been stolen, do
> you believe the dog is the thief?  Network manager triggers dhclient, and
> dhcdbd, but that doesn't mean that it's the culprit.

Hmmm, when repeated experiments have the same outcome, with 100%
repeatability, and the culprit explicitly puts its fangmarks on the
file, then it's time to do the inverse test, by removing the mongrel.
Since that led to /etc/resolv.conf being unmolested 100% of the time,
it was sufficiently proven that NM was the cause.

It matters not a jot whether NM caused the problem partly by
subcontracting. It initiated the harm, and left its fangmarks at the
scene of the crime.

> > There was however, more than circumstantial evidence. Here is 
> > one line in the file that I left for posterity:
> > 
> > $ head -1 /etc/resolv.conf
> > # generated by NetworkManager, do not edit!
> 
> That's the best evidence - except I can find no sign that Network manager
> actually wrote that, and it's an absolute certainty that dhclient IS
> writing that file.

It might have been possible that dhclient was writing
"# generated by NetworkManager, do not edit!", except for:

$ strings /sbin/dhclient | grep -i manager
x-display-manager

I no longer have NetworkManager to snoop on, but others have now also
confirmed the overwriting of /etc/resolv.conf, presumably with later
versions, since the inserted comments differ.

Erik

-- 
The ultimate barrier is one's viewpoint.
      - Terry Pratchett, _The Dark Side of the Sun_