How to control boot order when one boot partition is shared by two Fedora?

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1

I have two Fedora installed to the same disk - two separate rootfs btrfs subvols, and sharing the same boot subvol.

$ sudo tree /boot/loader/entries/
/boot/loader/entries/
├── 9c3180972d684d3ca465b6f860576696-0-rescue.conf
├── 9c3180972d684d3ca465b6f860576696-5.13.0-0.rc6.20210617git70585216fe77.48.fc35.x86_64.conf
├── f9ea3b2568b54649b0d964d39efafa77-0-rescue.conf
├── f9ea3b2568b54649b0d964d39efafa77-5.12.10-300.fc34.x86_64.conf
└── f9ea3b2568b54649b0d964d39efafa77-5.12.11-300.fc34.x86_64.conf

By default, grub menu will show <9c> before <f9>, so <9c> will be booted first.

How can I have grub to boot latest kernel version of <f9> by default?

What needs to be done when there are kernel updates?

Should I make changes when <f9> is booted, or when <9c> is booted?

2

I believe whichever received the last kernel update should be the one which is booted by default. Having 2 different fedora versions means you must do something every time the kernel is updated to keep your boot order since grub gets updated with the new kernel. With them sharing a boot partition you have volunteered yourself to do a lot of extra admin with the (almost) weekly kernel updates.

3

Is that easily done with grub? You can set the boot order but it is an index value which in your case will change as kernels get installed/removed.

If nobody else has an easy way to do it in grub you might consider switching boot loaders. With systemd-boot you can set the default entry using a wild card which solves that problem.

As a last resort I suppose you could change the machine-id for one of the installs so it came alphabetically first.

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4

Yes. That’s why I am asking for experience sharing.

5

systemd-boot will be my next target to try.

I just want to see if there is a way with grub to doing it.

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