sys-apps/systemd requires manual edit of /boot/grub/grub.cfg to add "init=/bin/systemd". But each time grub2-config may overwrite my manual edit. It would be great to add an option to grub2-config to read default kernel options from /proc/cmdline
But why, if you want to alter the cmdline just set it at /etc/default/grub The same way i set my setup there: GRUB_CMDLINE_LINUX="rootfslinux=ext4 dolvm" Why should it automagically read from /proc/cmdline... I am inclined to close this as wontfix, because you have quite convenient and correct way how to set this. But feel free to convince me that writing the entry to the above file is lame.
Well, this options is a bit like kernel's "make oldconfig" option. But you are right, for my issue, I can just edit /etc/default/grub. So Please mark it WONTFIX :-)
The problem with this being automatically detected is that you might have booted kernel you don't want the opitons from. Thats why it explicitly wants YOU as user to mess with it, and take all the blame for messed configuration :P Closing as per above.