Re: Debian 8 and Debian 9 Dual Boot

[Dan Norton <dnorton@mindspring.com>]

On 12/23/2017 04:35 PM, Felix Miata wrote:

Dan Norton composed on 2017-12-23 15:12 (UTC-0500):

Felix Miata wrote:

[...]
It's not so easy to figure out when POST is over with UEFI. Here, it seems
efibootmgr -t provides extra delay beyond what the BIOS defines for you to make
a selection from its own boot device selection menu, which requires an F12
keystroke here to see.

The timeout after appearance of Grub's menu is supposed to be controlled by
/etc/default/grub's GRUB_TIMEOUT=, which shows up here in Stretch's grub.cfg
first on line 86, a few lines before "### END /etc/grub.d/00_header ###".

Edited /etc/default/grub to change GRUB_TIMEOUT to 11:
root@BR914:/etc/default# nano grub

Observed "If you change this file, run 'update-grub' afterwards..." :
root@BR914:/etc/default# update-grub
Generating grub configuration file ...
Found background image: /usr/share/images/desktop-base/desktop-grub.png
Found linux image: /boot/vmlinuz-3.16.0-4-amd64
Found initrd image: /boot/initrd.img-3.16.0-4-amd64
Found Debian GNU/Linux (9.3) on /dev/mapper/vol2-root
Found Debian GNU/Linux (buster/sid) on /dev/mapper/vol3-root
done

Looking at /boot/grub/grub.cfg, timeout is mentioned as follows:
if [ "${recordfail}" = 1 ] ; then
   set timeout=-1
else
   if [ x$feature_timeout_style = xy ] ; then
     set timeout_style=menu
     set timeout=11
   # Fallback normal timeout code in case the timeout_style feature is
   # unavailable.
   else
     set timeout=11
   fi
fi

...but there is no effect. The timeout when rebooting is still 3 
seconds. I'm no shell expert so I don't know how to interpret the above.

What exactly is on the screen during those 3 seconds?

The menu inside the box is:
Debian GNU/Linux
Advanced options for Debian GNU/Linux
Debian GNU/Linux 8 (jessie) (on /dev/mapper/vol1-root)
Advanced options for Debian GNU/Linux 8 (jessie) (on /dev/mapper/vol1-root)
Debian GNU/Linux buster/sid (on /dev/mapper/vol3-root)
Advanced options for Debian GNU/Linux buster/sid (on /dev/mapper/vol3-root)

The first two boot stretch, so they will eventually have "9 (stretch) (on /dev/mapper/vol2-root)" appended, once the timeout is under control.

[...]