---
title: Migrating from setups where GbE size differs
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Please check the size of the corresponding GbE file for your board. Dell
typically uses 16KB GbE files, but some other coreboot distros will shrink
this to 8KB; they may also then shrink the GbE region, and make the BIOS
region at least 8KB bigger. Generally speaking, you will not find an image
elsewhere with a *smaller* BIOS region than in RBoot, because RBoot
makes sure to use the vendor's default flash layout (default region sizes).

If your GbE region size differs from what's used in RBoot, then you should
avoid use of the `./mk inject` command to inject MAC addresses; please
run [nvmutil](nvmutil.md) manually, extracting it using the guidance there
and then reinserting it.

The safest thing to do is to only flash the BIOS region, when switching from
other coreboot distros:

```
flashprog -p PROGRAMMER --ifd -i bios -w rboot.rom
```

If your region layout matches the vendor (Dell), then it should be safe to
use the inject command for changing MAC addresses. It is only a minor
convenience, as running nvmutil manually is quite easy. Refer to the guide.

More about this is covered in [another guide](ivy_has_common.md).


[//]: # "SPDX-License-Identifier: GFDL-1.3-or-later"