This post shows how to modify the EFI boot timeout and delete boot managers from a UEFI boot menu.
The application to use is
efibootmgr. Just by typing the command, as root, you should see a printout of the EFI boot menu and other details. Below is an example
[kamit@hu ~]$ sudo efibootmgr BootCurrent: 0005 Timeout: 1 seconds BootOrder: 0005,0004,0000,0009,0003,0002,0001 Boot0000* ubuntu Boot0001* fedora Boot0002* Fedora Boot0003* Fedora Boot0004* Windows Boot Manager Boot0005* antergos Boot0009* Hard Drive
BootCurrent is the running operating system, the one you are logged into.
Timeout is the time in seconds between when the boot manager appears on the screen and when it boots an entry from BootOrder.
BootOrder is the order of appearance of the entries in the boot menu.
The numbers are hexadecimal pointers to the boot manager entries.
To modify the timeout, type (t is time in seconds):
sudo efibootmgr -t 15
To delete a specific entry, type (0003 is the hex number for the specific entry that's going to be deleted):
sudo efibootmgr -b 0003 -B