dhclient is supposed to use the scripts at /etc/dhcp/dhclient-enter-hooks.d/
when it starts.

This works fine with dhclient -v <interface>. However, when using dhclient -cf
<conf_file> <interface>, the hook scripts are not used.

This can be seen below, where the use of the the -cf option doesn't use
resolvconf to update /etc/resolv.conf, but when I omit the -cf flag everything
works fine.

I don't see any option in the default config that enables this, so I'm assuming
it's a bug.

~ > sudo dhclient -v -cf /var/lib/wicd/dhclient.conf wlan0
Internet Systems Consortium DHCP Client 4.3.5
Copyright 2004-2016 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/wlan0/60:67:20:c7:1b:d0
Sending on   LPF/wlan0/60:67:20:c7:1b:d0
Sending on   Socket/fallback
DHCPREQUEST of 192.168.1.106 on wlan0 to 255.255.255.255 port 67
DHCPACK of 192.168.1.106 from 192.168.1.1
RTNETLINK answers: File exists
bound to 192.168.1.106 -- renewal in 110002 seconds.
~ > cat /etc/resolv.conf
nameserver 192.168.1.1
~ > sudo dhclient -v wlan0
Internet Systems Consortium DHCP Client 4.3.5
Copyright 2004-2016 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/wlan0/60:67:20:c7:1b:d0
Sending on   LPF/wlan0/60:67:20:c7:1b:d0
Sending on   Socket/fallback
DHCPREQUEST of 192.168.1.106 on wlan0 to 255.255.255.255 port 67
DHCPACK of 192.168.1.106 from 192.168.1.1
RTNETLINK answers: File exists
bound to 192.168.1.106 -- renewal in 99741 seconds.
~ > cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 192.168.1.1
nameserver 127.0.0.1

Dear submitter,

as the package isc-dhcp has just been removed from the Debian archive
unstable we hereby close the associated bug reports.  We are sorry
that we couldn't deal with your issue properly.

For details on the removal, please see https://bugs.debian.org/1143544

The version of this package that was in Debian prior to this removal
can still be found using https://snapshot.debian.org/.

Please note that the changes have been done on the master archive and
will not propagate to any mirrors until the next dinstall run at the
earliest.

This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmaster@ftp-master.debian.org.

Debian distribution maintenance software
pp.
Thorsten Alteholz (the ftpmaster behind the curtain)