/usr/ is in initramfs-tools-ubuntu-core 0.7.43.
This file is owned by root:root, with mode 0o755.
..
/usr/share/initramfs-tools/scripts/local-premount/
/usr/share/
/usr/share/initramfs-tools/
/usr/share/initramfs-tools/scripts/
/usr/share/initramfs-tools/scripts/local-premount/resize
/usr/share/initramfs-tools/scripts/local-premount/dragonmac
/usr/share/initramfs-tools/scripts/ubuntu-core-rootfs
/usr/share/initramfs-tools/modules.d/
/usr/share/initramfs-tools/modules.d/ubuntu-core-rootfs
/usr/share/initramfs-tools/hooks/
/usr/share/initramfs-tools/hooks/resize
/usr/share/initramfs-tools/hooks/ubuntu-core-rootfs
/usr/share/initramfs-tools/conf.d/
/usr/share/initramfs-tools/conf.d/ubuntu-core-rootfs
/usr/share/doc/
/usr/share/doc/initramfs-tools-ubuntu-core/
/usr/share/doc/initramfs-tools-ubuntu-core/changelog.gz
/usr/share/doc/initramfs-tools-ubuntu-core/copyright
/usr/share/man/
/usr/share/man/man5/
/usr/share/man/man5/writable-paths.5.gz