/usr/share/build-essential/essential-packages-list is in build-essential 12.1ubuntu2.
This file is owned by root:root, with mode 0o644.
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 | This list was generated on Sun Aug 2 13:14:19 UTC 2015 for amd64
It contains a list of essential packages (which are also build-essential).
base-files
base-passwd
bash
bsdutils
coreutils
dash
debianutils
diffutils
dpkg
e2fsprogs
findutils
grep
gzip
hostname
init
libc-bin
login
mount
ncurses-base
ncurses-bin
perl-base
sed
tar
util-linux
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