This parameter is used to configure the network in the initrd, but
we don't need it. startup-rescue 0.50 no longer requires this
parameter.
See https://bugzilla.altlinux.org/50526

This variable was need for rEFInd (it no longer support). The
variable was added to grub menu, but was not in needed.
In server V, this has remained since rEFInd.

This option is only for gfxboot on syslinux. It hides the options
to the left of it from the user.

This is not required for grub >= 2.04.

The 'splash=0' parameter not only disables splash, but also switches
to tty5 on which plymouth is supposed to run. This looks like a bug
in propagator. 'nosplash' is also a general parameter for propagator
and make-initrd.

For install2, this is needed to work around error 99-cdrom.sh with method:cdrom.
The error shows up with make-initrd-bootchain, but not propagator, as lowmem is
enabled for propagator in this mode.
For rescue, the point is that the latter has become quite large, so by default
it would be better that way.

At the moment, the ability to select the kernel with which to boot is
implemented only for grub (grub-pc, grub-efi, ieee1275boot).
note that renamed STAGE1_KFLAVOUR to STAGE1_KFLAVOURS, as multiple
kernels can now be added.

Needed for use one grub.cfg config for all grub platforms.

Pay attention to what you are adding to the variable. No need to
add language and live_rw there! Они нужны только для refind.

These changes allow you to create two independent config at the same
time or separately. It will be possible to add support for grub-pc in
the future.