grub2-mkconfig isn't generating correct mount paths (and also how do I get rid of extra kernels I don't use anymore?)

Question

Part of my recently auto-generated grub file is

menuentry 'Fedora (4.15.0-rc3+) 27 (Workstation Edition)' --class fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-4.15.0-rc3+-advanced-d5882dba-97be-48b3-a49e-745751c0c28e' {
        load_video
        insmod gzio
        insmod part_gpt
        insmod lvm
        insmod ext2
        set root='lvmid/2Wagdx-NqX3-0XjZ-E0KB-kFjL-681l-r2Jrr9/xh2Nk7-zisd-PwAb-qEp6-2nrV-kolN-e93RHx'
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint='lvmid/2Wagdx-NqX3-0XjZ-E0KB-kFjL-681l-r2Jrr9/xh2Nk7-zisd-PwAb-qEp6-2nrV-kolN-e93RHx'  d5882dba-97be-48b3-a49e-745751c0c28e
        else
          search --no-floppy --fs-uuid --set=root d5882dba-97be-48b3-a49e-745751c0c28e
        fi
        linuxefi /boot/vmlinuz-4.15.0-rc3+ root=/dev/mapper/linux-fedora ro rd.lvm.lv=fedora/root rd.lvm.lv=fedora/swap rhgb quiet rd.driver.blacklist=nouveau iommu=1 amd_iommu=on rd.driver.pre=vfio-pci
        initrdefi /boot/initramfs-4.15.0-rc3+.img
}

Note part of line 13:

linuxefi ... root=/dev/mapper/linux-fedora ro rd.lvm.lv=fedora/root rd.lvm.lv=fedora/swap blah blah blah

Now the Linux stuff on my machine is in an LVM group that used to be called fedora and was divided into two volumes: root and swap. Which is why you see

rd.lvm.lv=fedora/root

and

rd.lvm.lv=fedora/swap

But when I added a Ubuntu install, I changed the group name to root, and it now has 3 volumes: fedora, ubuntu, and swap. But whenever I generate a new grub file, it doesn't seem to remember these new names. The fix is easy enough: just change the line to the correct mountpoints during boot, then manually fix it when the Fedora boots. But I'm annoyed that I have to keep doing this every few weeks when I compile a new kernel and have to update grub.

Which brings me to a quick sidebar: (How do I remove kernels I don't use anymore? My grub menu is so cluttered right now)

So long story short: Where are the references to the old naming conventions of my LVM group?

Answer 1

For those who found this question on Google:

You can edit the file "/etc/default/grub". Look for the line starting with "GRUB_CMDLINE_LINUX"