Gentoo Archives: gentoo-user

From: Alan McKinnon <alan.mckinnon@×××××.com>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] /etc/hosts include file?
Date: Fri, 08 Mar 2013 08:34:46
In Reply to: Re: [gentoo-user] /etc/hosts include file? by Michael Mol
1 On 08/03/2013 02:29, Michael Mol wrote:
2 > On 03/07/2013 05:24 PM, Alan McKinnon wrote:
3 >> Anyone know if there's a way to get /etc/hosts to support the notion of
4 >> an include file? I did my homework and found nothing, maybe someone else
5 >> knows more.
6 >>
7 >> I really do need this, I have an app that discovers things on the
8 >> network and knows their address. This makes it's automated way into DNS
9 >> but takes a few days, and another app needs to use the fqdn right now.
10 >> So /etc/hosts is the way to go for the interim three days.
11 >>
12 >> I've worked around it by creating /etc/hosts.d/ containing a header and
13 >> a data file. cat the two and redirect to /etc/hosts.d/hosts and the real
14 >> hosts file is a symlink to that. It's a sub-directory as none of these
15 >> apps run as root and only root can modiy the real hosts file.
16 >>
17 >> This works well enough, but a supported include mechanism would make
18 >> life so much simpler, not to mention easier for my colleagues to
19 >> understand what the blazes I set up :-)
20 >
21 > No, there's not an "include" directive.
22 >
23 > There are, however, two other ways to get hostnames recognized.
24 >
25 > The first is /etc/resolv.conf . You can point your host at a local DNS
26 > server which is aware of the discovered hosts, and which forwards the
27 > rest of the queries. (This is how Samba 4's internal DNS server
28 > operates; anything it knows, it responds to. Everything else, it forwards.)
29 >
30 > Read the manpage for resolv.conf...there's a lot of stuff in there
31 > you'll want to know as you start coping with IPv6. (And some useful
32 > stuff if you want to favor a particular IP range...)
34 And the day started off so well. Then you had to come along and mention
35 IPv6.... :-)
37 IPv6 is wonderfully easy to use client-side and reasonably easy to plug
38 into an existing network (the routers mostly know what to do already).
39 The fun starts when you need to write an app that tracks and does range
40 allocations at ISP scale, all while keeping the PTRs in line too. Sadly
41 for me, my team works in that area and such a magic app is one of our
42 deliverables
44 One day when I've climbed down off the walls and my fingernails have
45 grown back, I might be up to relating what it is taking to get that
46 done.... :-)
48 >
49 > The second is /etc/nsswitch.conf . nsswitch.conf is how you inject
50 > samba-discovered, NIS-offered -- or whatever provider you care to inject
51 > -- hostname databases into the system resolver. You could have it query
52 > your provided database first, moving on to other sources if your
53 > provided database doesn't have what you're looking for. (I'm actually
54 > kinda surprised avahi doesn't come with an nss plugin...)
56 One day I should read nsswitch's man page completely. I never needed to
57 know more than "dns files" for the hosts directives and that shadow does
58 user. All those other lookup schemes are things I never use.
63 --
64 Alan McKinnon
65 alan.mckinnon@×××××.com


Subject Author
Re: [gentoo-user] /etc/hosts include file? Michael Mol <mikemol@×××××.com>