manually fixing IPs

[Dan Williams]

On Fri, 2011-04-01 at 05:20 +0200, Ralf Corsepius wrote:
> On 03/31/2011 07:28 PM, Dan Williams wrote:
> > On Sun, 2011-03-27 at 17:57 +0200, Ralf Corsepius wrote:
> >> On 03/27/2011 05:27 PM, Chuck Anderson wrote:
> >>> On Sun, Mar 27, 2011 at 03:58:06PM +0200, Ralf Ertzinger wrote:
> >>>> Hi.
> >>>>
> >>>> On Sun, 27 Mar 2011 15:48:14 +0200, Kevin Kofler wrote
> >>>>> NM supports static IPs these days. So I think that rather than
> >>>>> hacking around NM, you should just fix the IP inside NM's
> >>>>> configuration and have NM work FOR you rather than AGAINST you.
> >>>>
> >>>> I'm sorry, but by the time I have clicked through the GUI to do
> >>>> that I have configured the interface via ip, did what I wanted to
> >>>> do and unconfigured the interface again.
> >>>>
> >>>> I uncheck "Enable networking" in nm-applet before doing that,
> >>>> and for me that makes NM keep it's grubby paws off my manually
> >>>> configured interface, so I'm not complaining.
> >>>
> >>> You don't need to use the GUI.  Just edit
> >>> /etc/sysconfig/network-scripts/ifcfg-* with a static IP and NM will
> >>> pick it up right away and configure it.
> >>
> >> And how to tweak /etc/sysconfig/network-scripts/ifcfg-* (and/or
> >> /etc/sysconfig/network) for static IPs such that NM sets
> >> hostname/domainname correctly?
> >
> Let me try to provide more details:
> 
> Given a small (3 machines), wired (No WLAN, no VPN), static network 
> without dhcp and static IPs only, on a subnet of a larger network 
> (provides DNS), which is supposed to appear on a (private) domain of its 
> own (It's a lab's network).
> 
> When adding a Fedora machine,
> * with the "network" scripts it was possibile to assign the domainname 
> through /etc/sysconfig/network.
> - "hostname" returned "<machine>",
> - "hostname -f" returned "<machine>.<privatedomain>"

man hostname:

       The function gethostname(2) is used to  get  the  hostname.   When  the
       hostname  -a,  -d,  -f or -i is called will gethostbyname(3) be called.
       The difference in gethostname(2) and gethostbyname(3) is that  gethost‐
       byname(3)  is  network  aware,  so  it  consults /etc/nsswitch.conf and
       /etc/host.conf to decide whether to read  information  in  /etc/syscon‐
       fig/network or /etc/hosts

So here's what you do.  Set your hostname to "happy" by
modifying /etc/sysconfig/network:

HOSTNAME=happy

and update your /etc/hosts file to include this line:

127.0.0.1 happy.foobar.com happy localhost.localdomain localhost

Then, 'hostname' will return "happy", and "hostname -f" will return
happy.foobar.com as you desire.

But note that 'man hostname' also says:

       It is not possible to set the FQDN or the DNS domain name with the dns‐
       domainname command (see THE FQDN below).

and further:

       You can't change the FQDN (as returned by hostname --fqdn) or  the  DNS
       domain  name (as returned by dnsdomainname) with this command. The FQDN
       of the system is the name that the resolver(3)  returns  for  the  host
       name.

       Technically:  The  FQDN is the name getaddrinfo(3) returns for the host
       name returned by gethostname(2).  The DNS domain name is the part after
       the first dot.

       Therefore  it  depends on the configuration (usually in /etc/host.conf)
       how you can change it. Usually (if the hosts file is parsed before  DNS
       or NIS) you can change it in /etc/hosts.

       If  a machine has multiple network interfaces/addresses or is used in a
       mobile environment, then it may either have multiple FQDNs/domain names
       or  none  at  all.  Therefore  avoid  using  hostname  --fqdn, hostname
       --domain and dnsdomainname.  hostname --ip-address is  subject  to  the
       same limitations so it should be avoided as well.

So basically, if you don't have control over your DNS setup, you can't
control your FQDN (obviously).  If you have a small network, you
probably *do* want to set your machine hostname to the FQDN if you for
any reason need FQDNs at all.  Otherwise you get to keep /etc/hosts up
to date between all machines.

Dan

> * with NM, when
> - using a fqn as hostname in
> /etc/sysconf/networking-scripts/ifcfg*eth0 (rsp. nm-connection-editor), 
> both "hostname" and "hostname -f" always return the FQDN:
> "<machine>.<privatedomain>"
> - using "<machine>" as hostname in
> /etc/sysconf/networking-scripts/ifcfg*eth0 rsp. nm-connection-editor, 
> "hostname" returns "<machine", while "hostname -f", thoughout the years 
> sometimes returned "<machine>", sometimes an empty string, sometimes 
> "localhost" and sometimes even hung.
> 
> I don't know the exact causes. We've tried various things, but never 
> could make NM working as desired.
> 
> In other words, my question is:
> How to configure NM in a private, dhcp-less, static network, with only 
> static IPs, such that
> "hostname" returns "<machine>" and
> "hostname -f" returns "<machine>.<privatedomain>"
> 
> > domainname is only used for NIS,
> Hmm, this doesn't match with my understanding. Domainname and 
> ypdomainname are separate things. Domainname is the "domain part" of a 
> "FQDN", while ypdomainname is complete independent from the domainname 
> and may be set to something entirely different than "domainname".
> 
> > which I assume you're not running.
> We are using yp/NIS for this private network, but currently are not 
> using it for hostname resolution.
> 
> > Otherwise, if you have a persistent hostname set
> > in /etc/sysconfig/network (HOSTNAME=adasdasdf) then NM will respect
> > that.  If you do not have a persistent hostname set, then the hostname
> > will come from the DHCP server, or if not available from DHCP, from
> > reverse DNS lookup of your IP address, just as with the 'network'
> > service.
> 
> > NM will update your /etc/resolv.conf with various domains taken from
> > your hostname, so if your hostname is "blah.foobar.com", NM will add
> > "foobar.com" to the searches in /etc/resolv.conf.
> >
> > As has been stated before, NM does not touch /etc/hosts anymore.
> 
> Could you tell me since when? The machines in question are running F13 (
> 
> Ralf