Re: Merging sda1/sda2 partitions in YAST without losing grub boot on sda3
I would just delete partition 1 and 2. And then create a new partition 1. That will give you what you want.
You will then have "/dev/sda1" and "/dev/sda3" but no "/dev/sda2". The partition numbering is based on the slot used in the partition table, and not on the relative position on the physical disk.
If you are set for booting from a partition, that should still work (as long as "/dev/sda3" is still flagged as the active partition). However, I would recommend having a bootable USB live system available in case you need to boot it for repairs.
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