See following output from my system (Debian 8.6):
root@debian:~# cat /etc/debian_version
8.6
root@debian:~# pgrep -af dhc
506 dhclient -v -pf /run/dhclient.eth1.pid -lf /var/lib/dhcp/dhclient.eth1.leases eth1
447 dhclient -v -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases eth0
601 dhclient -v -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases eth0
664 dhclient -6 -pf /run/dhclient6.eth0.pid -lf /var/lib/dhcp/dhclient6.eth0.leases eth0
root@debian:~# grep -n -C3 eth0 /etc/network/interfaces
7-auto lo
8-iface lo inet loopback
9-
10:allow-hotplug eth0
11:iface eth0 inet dhcp
12:iface eth0 inet6 dhcp
13- accept_ra 1
14-
15-allow-hotplug eth1
root@debian:~#
There are 2 `dhclient` processes running for `eth0` (IPv4). Rebooting does not help for me.
Thanks.