Re: Question to new network device names
On Thu 24 Aug 2017 at 20:58:18 (-0400), Gene Heskett wrote:
> On Thursday 24 August 2017 12:30:37 Dan Ritter wrote:
> > On Thu, Aug 24, 2017 at 10:43:56AM -0500, David Wright wrote:
> > > The history of computing is littered with statements like
> > > "virtually every computer has exactly one or two NICs".
> >
> > It used to be zero.
> >
> > We are currently in the phase of history where this statement is
> > true. NICs are both ubiquitous and cheap, yet devices tend to
> > come with one (only an ethernet port or only a wifi radio) or
> > two (one of each of those, or a wifi radio and a cell radio).
> >
> > Devices can add more, but they are always special cases: my
> > Debian-running firewall has 5 ethernet ports. I occasionally
> > add a USB ethernet frob in order to isolate a device that I want
> > to talk to directly. Special cases deserve special treatment.
> >
> > I expect the statement to remain true for the next ten years.
> >
> > Do you expect differently? If so, why?
> >
> > > This list is full of postings about the complex DNS system. But
> > > how long did /etc/hosts last? Some complexity is unavoidable,
> > > but if you try to avoid it, you pay for it later. Look at timezones.
> > > Ever allowing computers' internal clocks to run on local time
> > > was, with hindsight, a big mistake. Leap seconds might also
> > > be seen the same way (still under debate).
> >
> > /etc/hosts still acts the way it always did -- put in an entry,
> > it overrides DNS.
> >
> That depends entirely on who wrote your /etc/resolv.conf and whether or
> not your did a sudo chattr +i /etc/resolv.conf, immediately after
> verifying that it works. (and of course that implies it is a real file,
> not a softlink to something else. With N-M in the mix and active that
> is the only way to keep it from tearing down your network configuration
> and leaving you empty files, and no network, if it cannot find a dhcpd
> server)
(We've heard about your problems concerning /etc/resolv.conf
several times now.)
I think the file that affects the priority of /etc/hosts is
/etc/nsswitch.conf which typically contains a line like:
hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
But that misses the point I was making, which requires one to know
a fragment of Internet history. /etc/hosts started life as a file
containing the address of every host on the network (then ARPANET).
Simple, sufficient at the time, but obviously not going to stay
the course.
Similarly, /dev/sdX just about works well enough for simple, static
systems but not for more complex, dynamic ones; eth0 likewise is
showing its age for scaling and flexibility, particularly as the
newer scheme adds functionality without removing the legacy.
Cheers,
David.
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