/etc/network/interfaces

# dpkg -S "/etc/network"
ifupdown, bind9: /etc/network

# dpkg -s ifupdown
Package: ifupdown
Status: install ok installed
Priority: important
Section: admin
Installed-Size: 217
Maintainer: Guus Sliepen <guus@debian.org>
Architecture: amd64
Multi-Arch: foreign
Version: 0.8.35
Replaces: systemd (<< 228-3~)
Depends: libc6 (>= 2.14), lsb-base, adduser, iproute2
Recommends: isc-dhcp-client | dhcp-client
Suggests: ppp, rdnssd
Breaks: systemd (<< 228-3~)
Conffiles:
 /etc/default/networking 3f34a1868c2e6cd41caec70c8d1e5659
 /etc/init.d/networking 11adb3f76369f48e5a8432f8bf8abfd7
Description: high level tools to configure network interfaces
 This package provides the tools ifup and ifdown which may be used to
 configure (or, respectively, deconfigure) network interfaces based on
 interface definitions in the file /etc/network/interfaces.

# dpkg-query -L ifupdown
/.
/etc
/etc/default
/etc/default/networking
/etc/init.d
/etc/init.d/networking
/etc/network
/etc/network/if-down.d
/etc/network/if-post-down.d
/etc/network/if-pre-up.d
/etc/network/if-up.d
/etc/network/interfaces.d
/lib
/lib/ifupdown
/lib/ifupdown/settle-dad.sh
/lib/ifupdown/wait-for-ll6.sh
/lib/ifupdown/wait-online.sh
/lib/systemd
/lib/systemd/system
/lib/systemd/system/ifup@.service
/lib/systemd/system/ifupdown-pre.service
/lib/systemd/system/ifupdown-wait-online.service
/lib/systemd/system/networking.service
/lib/udev
/lib/udev/ifupdown-hotplug
/lib/udev/rules.d
/lib/udev/rules.d/80-ifupdown.rules
/sbin
/sbin/ifup
/usr
...