Comment 0 for bug 1717983

dhclient has been used as the dhcp client in Ubuntu and debian for
many years. Over time, many packages have integrated with dhclient.
The list below is of packages that have declared a dependency and
those that have shipped hooks to be invoked by dhclient.

As we move to systemd-networkd these will have to be addressed.

# ./get-rdeps isc-dhcp-client | sort -u
breaks - initramfs-tools (initramfs-tools)
depends - dracut (dracut-network)
depends - isc-dhcp (isc-dhcp-client-ddns)
depends - libguestfs (libguestfs0)
depends - maas (python3-maas-provisioningserver)
depends - netscript-2.4 (netscript-2.4)
depends - network-manager (network-manager)
depends - ubuntu-meta (ubuntu-minimal)
depends - walinuxagent (walinuxagent)
depends - whereami (whereami)
depends - wicd (wicd-daemon)
depends - wifi-radar (wifi-radar)
enhances - resolvconf (resolvconf)
recommends - avahi (avahi-autoipd)
recommends - ifupdown (ifupdown)
recommends - ifupdown2 (ifupdown2)
recommends - madwimax (madwimax)

$ apt-file search '/etc/dhcp/' | grep 'hooks.d/' | sed 's,:.*,,' | sort -u
avahi-autoipd
cloud-init
controlaula
ddclient
isc-dhcp-client
ntp
ntpdate
openresolv
resolvconf
samba-common
sendmail-base
systemd
whereami

Another possible integration point that is not likely listed in the package
dependencies is reading of the leases file for additional information.
As an example, Azure advertises the location of its http based metadata
service as an option in a dhclient response. cloud-init will read the
lease files to find the correct address.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: isc-dhcp-client 4.3.5-3ubuntu1
ProcVersionSignature: Ubuntu 4.12.0-11.12-generic 4.12.5
Uname: Linux 4.12.0-11-generic x86_64
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
ApportVersion: 2.20.7-0ubuntu1
Architecture: amd64
CurrentDesktop: GNOME
Date: Mon Sep 18 12:46:31 2017
DhclientLeases:

EcryptfsInUse: Yes
InstallationDate: Installed on 2015-07-23 (788 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Alpha amd64 (20150722.1)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: isc-dhcp
UpgradeStatus: No upgrade log present (probably fresh install)