[Lxc-users] How long the dhcp lease lasts

[Masood Mortazavi]

I find it best to separate, entirely, the base host cluster management
network from the container cluster network, entirely.


On Mon, Apr 22, 2013 at 2:46 PM, Michael H. Warfield <mhw at wittsend.com>wrote:

> On Mon, 2013-04-22 at 22:58 +0200, Robin Monjo wrote:
> > Thank you for your answer.
> > I want to have the hostname and ip written in the /etc/hosts file so I
> > can access them directly using their hostname and not their ip. For
> > example, I'd like to ping the hostname rather than the ip.
>
> But...  You should get that from dnsmasq and not need them
> in /etc/hosts.  That's the whole point of the DNS system.  Reliance
> on /etc/hosts is old old stuff that was intended to be replaced by the
> DNS system ages ago.  We should only need to rely on /etc/hosts for
> local things and very rare exceptional conditions.
>
> > I will document myself on dnsmasq to get a better understanding of
> everything.
>
> Cool.  In most cases, dnsmasq can deal with DNS issues.  You have to be
> sure that your host server references it, though, in /etc/resolv.conf
> (i.e. "nameserver 127.0.0.1) or it won't now where to ask.  You then
> configure other domains under /etc/dnsmasq.d/ since dnsmasq is a limited
> forwarding / caching server.  To go "full bore" will a full dns server
> and dhcp server, you would use the dhcpd package and bind (Berkeley
> Internet Name Daemon) package but that's probably overkill in your case.
>
> Regards,
> Mike
>
> > On Apr 22, 2013, at 10:48 PM, Michael H. Warfield <mhw at WittsEnd.com>
> wrote:
> >
> > > On Mon, 2013-04-22 at 21:59 +0200, Robin Monjo wrote:
> > >> Hello everyone,
> > >>
> > >> Using the default config, containers will have their IP attributed by
> > >> the dnsmasq service. I'd like to write in the '/etc/hosts' file of the
> > >> host system the hostname and the corresponding IP address of each
> > >> container I start.
> > >
> > > Why?  If you're using dnsmasq, it's in the DNS cache of the dnsmasq
> > > server.  That's its purpose in life, to act as a DNS caching service.
> > > Why do you need it in /etc/hosts when you've already got in in DNS?
> > >
> > >> I will then use this hostname in an iptable rules for port forwarding.
> > >> But what if dnsmasq change an IP at the end of the lease ?
> > >
> > >> So the question is: how long an IP given by dnsmasq will last ?
> > >
> > > What is your lease expiration configured for?  I've used anything for a
> > > few hours (high turnover large WiFi sites) to several days to carry
> over
> > > a weekend along with static leases for servers and "permanent" devices.
> > > It depends on what you've configured it for.
> > >
> > >> May I see one of my container have its IP changed ?
> > >
> > > Maybe.  Depends on what you've configured it for.  I'm not so sure
> about
> > > dnsmasq acting as the dhcp server (which is what you are talking about)
> > > but dhcpd will notify you of things like this.  Most notably, you will
> > > get deletes on old name/addresses and adds for new name/addresses both
> > > forward and reverse, but it's all configuration driven.
> > >
> > >> Any ways to have the dnsmasq table synced with the /etc/hosts file
> > >> (container's host side) ?
> > >
> > > Again...  Why?  Use the DNS cache in dnsmasq.  You have no need to
> refer
> > > to /etc/hosts at all.
> > >
> > >> Kind regards
> > >
> > > Regards,
> > > Mike
> > > --
> > > Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
> > >   /\/\|=mhw=|\/\/          | (678) 463-0932 |
> http://www.wittsend.com/mhw/
> > >   NIC whois: MHW9          | An optimist believes we live in the best
> of all
> > > PGP Key: 0x674627FF        | possible worlds.  A pessimist is sure of
> it!
> >
> >
>
> --
> Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
>    /\/\|=mhw=|\/\/          | (678) 463-0932 |
> http://www.wittsend.com/mhw/
>    NIC whois: MHW9          | An optimist believes we live in the best of
> all
>  PGP Key: 0x674627FF        | possible worlds.  A pessimist is sure of it!
>
>
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