Grub related.

For EFI boot, there could be an independent directory and its grub.cfg.

Display on both monitor and ttyS2

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# Automatically created by OE
serial --unit=2 --speed=115200 --word=8 --parity=no --stop=1
default=0
timeout=2

menuentry 'boot-by-label'{
insmod ext2
search -n -l rootPartition -s
#linux /boot/vmlinuz-4.1.3 root=LABEL=rootPartition ro rootwait nomodeset consoleblank=0 console=ttyS2,115200n8
#linux /boot/vmlinuz-4.1.3 root=LABEL=rootPartition ro rootwait nomodeset consoleblank=0
linux /boot/vmlinuz-4.1.3 root=LABEL=rootPartition ro rootwait nomodeset consoleblank=0 console=tty0 console=ttyS2,115200n8
initrd /boot/initrd.img-4.1.3
}