Ubuntu – Add ro quiet splash to all entries

To add custom entries, the file you should edit is /etc/grub.d/40_custom.

The options are the same as in grub.cfg, but just in case here is a link with more info how to customize the file.

Actually, there are two files that need to be modified to solve this problem. I've tested this on my Lubuntu 16.04.1 and Manjaro Linux.

In Ubuntu:

1) File /usr/lib/linux-boot-probes/mounted/40grub2 there is a function parse_grub_menu that doesn't handle all initrd parameters. You need to modify 'case "$1" in ... initrd)':

a) remove assignment

initrd="$(echo "$2" ...)"

b) add two lines in place of the removed one:

shift 1
initrd="$(echo "$@" | sed 's/(.*)//')"

2) File /etc/grub.d/30_os-prober within a for loop fix the assignment of LINITRD:

for LINUX in ${LINUXPROBED}; do
...
    LINITRD="`echo ${LINUX} | cut -d ':' -f 5 | tr '^' ' '`"

The first fix takes all available initrd info for Manjaro into account. The second fix cleans up the generated initrd line by changing some '^' characters to spaces.