== How to force Solaris to renumber network devices

Let us suppose, as a not entirely hypothetical example, that you
are transplanting the system disks from a Solaris 10 install from a
SunFire X2100 to a SunFire X2200. While both machines have four onboard
network ports, two Broadcom and two nVidia, they are not quite the
same hardware, enough so that if left to its own devices Solaris will
consider the new machine's NICs to be _bge2_, _bge3_, _nge2_, and _nge3_
(instead of _bge0_, _bge1_, _nge0_, and _nge1_).

This isn't a really desirable result, because it makes the transplanted
machines different from any future machines you install on the X2200s
(and in turn means that you have to remember any particular install's
history when figuring out which network device is which). What you want
to do is to force Solaris to renumber the Ethernet devices from scratch,
giving them their natural numbers.

(As far as I can see, there is no documented way of doing this; a
reconfiguration reboot doesn't do it, at least on Solaris 10 U4 and U5.)

It turns out that Solaris stores this mapping information in
((/etc/path_to_inst)) in the relatively obvious form of:

> _"PATH" INSTANCE "DRIVER"_

The _PATH_ is relative to _/devices_, the _DRIVER_ is what you'd expect,
and the _INSTANCE_, for network devices, is the N in bgeN.  So what you
want to do is edit ((/etc/path_to_inst)) to remove all mention of your
network devices and do a reconfiguration reboot, which will recreate
them from scratch and should give them the numbers you want. It's
possible that you can just directly assign instance numbers to network
devices without the reconfiguration reboot, but I haven't tested this.

(Important: *make a backup of the file first*, just in case.)

When I did this it took two go-arounds to get the nVidia devices
correct; you might be able to get it down to one by doing the editing
in the rescue environment instead of booting the system into normal
single-user mode. If you go this route, you'll need to rebuild the boot
archive by hand (with '_bootadm update-archive -R /a_').

Oh yes, and here's an important safety tip that I learned the hard way:
~~under no circumstances should you use ((rem_drv))~~ (what can I say,
it looked like a tempting way to force a full reconfiguration of the
driver from scratch). Doing so removes the information about which PCI
devices are handled by the driver, which is hard to recover from unless
you have a spare Solaris 10 machine (ideally with the same hardware)
around to consult as reference.

(This mapping information is stored in ((/etc/driver_aliases)); the base
version of ((driver_aliases)) comes from the _SUNWcsd_ package but it's
then modified by the install scripts of various driver packages.)