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Re: Can't find the DNS Servers




On Tuesday 26 September 2017 09:09:47 Greg Wooledge wrote:

> On Mon, Sep 25, 2017 at 02:12:07PM -0700, Don Armstrong wrote:
> > On Mon, 25 Sep 2017, Greg Wooledge wrote:
> > > On Mon, Sep 25, 2017 at 12:20:45PM -0700, Don Armstrong wrote:
> > > > as is documented in dhclient-script(8):
> > >
> > > Well now that's just EVIL. :-(
> >
> > It's much more powerful than a single variable because you can have
> > it do *anything*.
>
> No, you don't understand.  I had no idea that man page EXISTED!
> For years, I have been searching back and forth and up and down in
> dhclient(8) and dhclient.conf(5) and finding NOTHING.
>
> Turns out the REASON I couldn't find anything was because some bright
> spark decided to split the documentation into multiple man pages.
>
> > > Well now that's just EVIL. :-(
>
> So, apparently the only way to find anything is to open umpteen
> terminal windows, one man page in each terminal window.  Jump to the
> bottom of each man page, find the SEE ALSO section, open EVERY linked
> man page in another terminal window.  Recursively.  Then perform your
> searches in every single window in parallel until one of them hits.
>
> So let's see... I'll assume dhclient(8) is the root of the search
> tree.  This links to dhcpd(8), dhcrelay(8), dhclient-script(8),
> dhclient.conf(5), dhclient.leases(5), dhcp-eval(5).  So now I need
> to open 6 more windows, or 7 total.
>
> dhcpd(8) doesn't exist, because this isn't a server, so make it 6.
>
> dhcrelay(8) doesn't exist.  Don't even know what that is.  5.
>
> dhclient-script(8) links to dhclient(8), dhcpd(8), dhcrelay(8),
> dhclient.conf(5), dhclient.leases(5).  No new windows.
>
> dhclient.conf(5) links to dhcp-options(5), dhcp-eval(5),
> dhclient.leases(5), dhcpd(8), dhcpd.conf(5).  dhcpd.conf(5) doesn't
> exist, so just one new window, for dhcp-options(5).  I'm up to 6 open
> now.
>
> dhclient.leases(5) links to dhclient(8), dhcp-options(5),
> dhclient.conf(5), dhcpd(8), dhcpd.conf(5).  No new ones.
>
> dhcp-eval(5) links to dhcpd.conf(5), dhcpd.leases(5),
> dhclient.conf(5), dhcp-options(5), dhcpd(8), dhclient(8). 
> dhcpd.leases(5) doesn't exist, so no new ones.
>
> dhcp-options(5) links to dhcpd.conf(5), dhcpd.leases(5),
> dhclient.conf(5), dhcp-eval(5), dhcpd(8), dhclient(8).  No new ones.
>
> So I've got my 6 terminal windows open.  I've spent 10 minutes so far,
> and I haven't even READ a single bit of any of the pages.  Just the
> SEE ALSOs.
>
> Now I get to try to wrack my brain for keywords, and repeat my keyword
> searches 6 times, once in every window.
>
> Turns out "resolv" (my first keyword) pops up in window #2, which is
> dhclient-script(8), and also in window #6, dhcp-options(5).
>
> From there, you can guess what the next steps are, because apparently
> you were already aware of the existence of dhclient-script(8).  If I'm
> lucky, I'll focus on that page rather than dhcp-options(5) which is
> very confusing, and seems to be talking in abstractions.  It sure as
> hell doesn't clearly define what options go in what files, nor even
> which options are for the client and which are for the server.  Their
> only mentions of resolv.conf are in a DHCPV6 section.  What the hell
> is DHCPV6?  Does it have something to do with IPv6?  How would I know
> whether I'm using DHCPV6 or not?  Try searching for V6 in the other
> five windows... nothing at all!  And so on.
>
> All this grief and agony because they couldn't just put all the
> information that THE MOST COMMON USE CASES will need into a single
> document.
>
> What are the most common use cases?  An excellent question.  Here's
> my guess:
>
> 1) Client is plugged into the network without being configured. 
> Simply uses whatever the DHCP server spits out.  If that's wrong, too
> bad.
>
> 2) Client uses what the DHCP server spits out, but the administrator
>    of the client will try to work around whichever bits of the DHCP
>    server's responses are wrong.  In my experience, it's the
> nameservers that are most likely to need local adjustment.  That's why
> you have this thread.  And all the previous threads.  And all the web
> pages out there that advise people to use chattr +i.  And all the
> people who use chattr +i.  And all the self-proclaimed experts who say
> "No, you're doing it wrong!" but then don't offer a better way.
>
> 3) Client uses what the DHCP server spits out, but the administrator
>    of the client is also the administrator of the DHCP server, and can
>    correct things in the DHCP server to make all the clients happy.
>
> The first use case needs no documentation at all.
>
> The second use case needs some way for the admin of the client to be
> able to search for resolv.conf in the documentation and actually FIND
> IT. I searched in dhclient(8) and in dhclient.conf(5) and fid not find
> it. I honestly, truly believed that I had done my best.  That I had
> put in the required effort.  That I had been intelligent and diligent
> and resourceful.  That I had given the software the benefit of the
> doubt, but this feature was simply not present, or not documented
> anywhere.
>
> The third use case... well, that's not me right now.  In the past I
> have set up a DHCP server on an OpenBSD machine, and found things to
> be fairly straightforward.  I was able to find the options I needed,
> and what file to put them in, and so on.  It's really obvious and
> simple where you put the nameservers when you have control of the
> server.
>
> It's clear that the INTENDED way is for the configuration to be done
> on the server.
>
> But, you see, most people DO NOT HAVE CONTROL OF THE SERVER.
>
> So, my conclusion based on my experiences was that the only way to
> configure ISC's DHCP to end up with correct nameservers on the client
> was to have control of the server, or to subvert the client's
> execution environment in such a way that dhclient cannot modify
> resolv.conf at all (e.g. chattr +i).
>
> I believed this for YEARS.
>
> And then you said this:
> > > > as is documented in dhclient-script(8):
>
> Which, by the way, is NOT referenced from dhclient.conf(5)'s SEE ALSO
> section.  Because, why would the primary client configuration document
> make it easy to find the instructions for configuring the client?
>
> > > Well now that's just EVIL. :-(
>
> And then you didn't even understand my response.  Which just shows how
> completely out of touch with each other the various groups are.

+ at least 10,000. This nail has been beat completely thru a 12" thick 
marble wall, and this gentleman has defined the problem that exists with 
many of the man pages, not exclusive to dhcp related stuffs, its an 
endemic linux virus that makes it 100x more difficult for the user who 
can read (and there are some who can read but not grok) to take the 
advantages offered and use them to get his job done without half a 
megabyte of pleading with a mailing list for enlightenment.

I'll give you the ip man page as another perfect example. I've never read 
a more obtuse manpage in my life. I get the impression the manpage 
writer is charged 10 dollars a word for emmiting anything over 100 
words.

The whole man pages tree on the install I am currently doing is 13 
megabytes.  The sd card its on is 32 gigabytes, so we'll have at least 
10 gigabytes we could use for man pages without impacting its ability to 
store and use a 300 kilobyte package, if they were just written to teach 
us what to do.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>