[Libguestfs] [PATCH] v2v: remove MAC address related information

[Fabien Dupont]

Apart from the MAC address, the network interface name may change. In my
tests, my network interface is renamed from ens160 in VMware to eth0 in RHV.

On 27 February 2018 at 14:01, Pino Toscano <ptoscano at redhat.com> wrote:

> On Tuesday, 27 February 2018 13:34:09 CET Richard W.M. Jones wrote:
> > On Tue, Feb 27, 2018 at 12:53:08PM +0100, Pino Toscano wrote:
> > > On Tuesday, 27 February 2018 12:35:36 CET Tomáš Golembiovský wrote:
> > > > Remove ties to MAC address because it is likely to change.
> > >
> > > v2v tries to preserve the MAC address of network interfaces; few months
> > > ago we did a fix regarding this:
> > > https://bugzilla.redhat.com/show_bug.cgi?id=1506572
> > >
> > > The approach of this patch is IMHO not good, since it removes the MAC
> > > address from the network-scripts, but still the rest of v2v will try
> > > to preserve the MAC addresses.
> >
> > We preserve the MAC address in metadata.  On the other hand AIUI this
> > patch only removes the association in the ifcfg files and the guest
> > will reassociate it when it boots (albeit it might then mix up the
> > ethernet interfaces so that's not good).
>
> Yes, this is my concern, i.e. that the guest network configuration
> might break.
>
> > There's IMHO a bigger problem which is not being addressed:
> >
> > https://bugzilla.redhat.com/show_bug.cgi?id=1318922
>
> Possibly there could be also
> https://bugzilla.redhat.com/show_bug.cgi?id=1451597
>
> > > What's the reason behind this patch?
> >
> > There's a bit of background which is missing.  Tomáš and I had some
> > discussions (privately, unfortunately) with the ManageIQ developers
> > who are integrating virt-v2v into MIQ/CloudForms.  Their existing
> > software runs a separate virt-sysprep step on guests after they have
> > been converted by virt-v2v.  They disable all sysprep the operations
> > except for just a couple, including ‘net-hwaddr’, so the effect is
> > roughly the same as this patch.
> >
> > The question was raised why they need to do that as a separate step
> > and why virt-v2v doesn't do it.
>
> This is what my question was about: I do not understand why this
> sysprep step (to remove the MAC addresses) is done in the first place,
> and without this information it is hard to put extra conversion steps
> in v2v.
>
> What issues were fixed by sysprep'ing the converted guest?
>
> > And indeed there was some discussion
> > about whether or not converted guests need a new MAC address -- it's
> > at best unclear -- it is thought that VMware might reuse MAC addresses
> > which have "left" the hypervisor, although no one knows if that's
> > really true or not.
>
> IMHO the first thing to do would be deciding on whether the MAC address
> need to be removed from the guest or not.
>
> If it is decided they need to go, then my suggestion would be to add a
> new command line option to tune this behaviour:
> - if not specified, then the MAC addresses are preserved in both guest
>   and metadata
> - if specified, then the MAC addresses will not be preserved even in
>   the metadata
>
> --
> Pino Toscano




-- 

*Fabien Dupont*

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Red Hat - Solutions Engineering

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