Below is probably easier to do with bectl/beadmin but still.
1. Install FreeBSD 14 following this guide (that also can be found as a howto in this Forum) but change zroot to zroot14 everywhere
2. Change the path when copying the efi bootloader
3. Add the size of the partition when doing this step (example shows 100G)
5. Boot FreeBSD15 from memstick and follow the same guide as in 1. Change zroot to zroot15. Change the size as wanted.
6. Change the path when copying the efi bootloader
8. Exit the installer, boot and enter BIOS. Make sure that both boot options for 14 and 15 are there. Pick the one you want to run and go.
/grandpa
1. Install FreeBSD 14 following this guide (that also can be found as a howto in this Forum) but change zroot to zroot14 everywhere
2. Change the path when copying the efi bootloader
cp /boot/loader.efi /mnt/EFI/freebsd14/freebsd14.efi
3. Add the size of the partition when doing this step (example shows 100G)
gpart add -a 1m -s 100G -t freebsd-zfs -l disk0 ada0
4. Complete the guide5. Boot FreeBSD15 from memstick and follow the same guide as in 1. Change zroot to zroot15. Change the size as wanted.
6. Change the path when copying the efi bootloader
cp /boot/loader.efi /mnt/EFI/freebsd15/freebsd15.efi
7. When in shell after the post installation step run the following from this thread: efibootmgr -c -a -L FreeBSD14 -l ada0p1:/efi/freebsd14/freebsd14.efi -e "rootdev=zfs:zroot14/ROOT/default:"
efibootmgr -c -a -L FreeBSD15 -l ada0p1:/efi/freebsd15/freebsd15.efi -e "rootdev=zfs:zroot15/ROOT/default:"
8. Exit the installer, boot and enter BIOS. Make sure that both boot options for 14 and 15 are there. Pick the one you want to run and go.
/grandpa