This file is indexed.

/lib/partman/update.d/20bootable is in ubiquity 18.04.14.

This file is owned by root:root, with mode 0o755.

The actual contents of the file can be viewed below.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
#!/bin/sh

. /lib/partman/lib/base.sh

dev=$1
num=$2
id=$3
size=$4
type=$5
fs=$6
path=$7
name=$8

cd $dev

if [ $fs = free ]; then
	rm -f $id/bootable
else
	bootable=no
	open_dialog GET_FLAGS $id
	while { read_line flag; [ "$flag" ]; }; do
		if [ "$flag" = boot ]; then
			bootable=yes
		fi
	done
	close_dialog

	if [ $bootable = yes ]; then
		mkdir -p $id
		>$id/bootable
	else
		rm -f $id/bootable
	fi
fi