Re: [Xen-users] mount DomU root fs via. NFS

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-08-01 at 09:45 +0100, Jeenu Viswambharan wrote:
> On Thu, Jul 31, 2014 at 09:53:32, xen-users-bounces@xxxxxxxxxxxxx wrote:
> > On Wed, 2014-07-30 at 18:03 +0100, Jeenu Viswambharan wrote:
> > >  I therefore instead chose to go with NAT instead.
> > >
> > > From [1], all that's to be done in Dom0 is to
> > >
> > >   echo 1 > /proc/sys/net/ipv4/ip_forward
> >
> > [1] also says you need to do
> >         iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
> > to enable NAT, otherwise you are just in regular routing mode.
> >
> > If you don't do that then you would have to arrange a subnet for your
> > VMs and appropriate routing tables in your external infrastructure
> > etc.
> 
> Uh, my init script was doing that too; I missed to mention it earlier.
> 
> The behaviour is reproducible - guest waits for the NFS mount and
> crashes. All I see in Dom0 dmesg pertaining to virtual interfaces is:
> 
>   [  262.676269] IPv6: ADDRCONF(NETDEV_UP): vif1.0: link is not ready
>   [  272.153571] IPv6: ADDRCONF(NETDEV_CHANGE): vif1.0: link becomes ready
> 
> I also have a virtual interface in Dom0 while the guest is alive:
> 
>   vif1.0  Link encap:Ethernet  HWaddr fe:ff:ff:ff:ff:ff
>           inet addr:192.168.1.128  Bcast:0.0.0.0  Mask:255.255.255.255
>           inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:32
>           RX bytes:0 (0.0 B)  TX bytes:468 (468.0 B)
> 
> If I'm reading this right, there were 6 packets received from the guest.
> How do we know what happened to these?

In general it's pretty hard :-(

> FWIW, `iptables -t nat -L` is:
> 
>   Chain PREROUTING (policy ACCEPT)
>   target     prot opt source               destination
> 
>   Chain INPUT (policy ACCEPT)
>   target     prot opt source               destination
> 
>   Chain OUTPUT (policy ACCEPT)
>   target     prot opt source               destination
> 
>   Chain POSTROUTING (policy ACCEPT)
>   target     prot opt source               destination
>   MASQUERADE  all  --  anywhere             anywhere
> 
> Anything suspicious here?

Nothing jumps out at me...

Does "iptables -L" show anything of interest?

vif-nat messes with routing tables etc too. Perhaps the outputs of ip
(link|route|addr) show will give someone a clue?

Can you also share your domU console logs so we can see exactly what is
going on please.

Ian.


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