[meta-rauc] How to generate update bundle: With genimage or with recipe?

[BAUER Bernd <bernd.bauer@ses-imagotag.com>]

Hi!

I use genimage for image generation.
This is an A/B system.
The bootloader is u-boot and switching the root partitions already works.

Looks something like this...
8<------------------------------------
image systemA.ext4 {
        size = 512M
        ext4 {
                label = "systemA"
        }
        mountpoint = "/"
}

image systemB.ext4 {
        size = 512M
        empty = true
        ext4 {
                label = "systemB"
        }
}

image log.ext4 {
        size = 128M
        empty = true
        ext4 {
                label = "log"
        }
}

image app.ext4 {
        size = 128M
        empty = true
        ext4 {
                label = "Application"
        }
}

image @IMAGE@ {
        hdimage {
                partition-table-type = "gpt"
                #gpt-location = 2M
        }

        partition bootloader {
                in-partition-table = false
                offset = 32K
                image = "u-boot.img"
        }

        partition systemA {
                in-partition-table = true
                bootable = true
                offset = 8M
                partition-type-uuid = "L"
                image = "systemA.ext4"
        }

        partition systemB {
                in-partition-table = true
                bootable = true
                partition-type-uuid = "L"
                image = "systemB.ext4"
        }

        partition log {
                in-partition-table = true
                partition-type-uuid = "L"
                image = "log.ext4"
        }

        partition app {
                in-partition-table = true
                partition-type-uuid = "L"
                image = "app.ext4"
        }
}
8<------------------------------------

Now I want to create an update bundle for one of the system partitions with rauc.
What is the best way to make the update bundle here?
With a recipe and "inherit bundle"?
Or should I do it with genimage?

I did this with a recipe and used my rootfs recipe as base.
Here I get an update bundle out, that is about 3GB big. This much too large.

Greets Bernd