Saat ingin melakukan upgrade, proses terhenti oleh insserv yang melakukan proses pembacaan terhadap urutan startup berdasarkan LSB tags, terhenti pada startup script milik snapvault, diakibatkan aplikasi snapvault yang script nya berada di /etc/init.d/snapvault tidak menambahkan LSB tags.

Berikut adalah logs …

Reading changelogs... Done
Extracting templates from packages: 100%
Preconfiguring packages ...
Setting up udev (215-17+deb8u6) ...
addgroup: The group `input' already exists as a system group. Exiting.
update-initramfs: deferring update (trigger activated)
insserv: warning: script 'snapvault' missing LSB tags and overrides
insserv: There is a loop between service monit and snapvault if stopped
insserv:  loop involving service snapvault at depth 2
insserv:  loop involving service monit at depth 1
insserv: Stopping snapvault depends on monit and therefore on system facility `$all' which can not be true!
insserv: exiting now without changing boot order!
update-rc.d: error: insserv rejected the script header
dpkg: error processing package udev (--configure):
 subprocess installed post-installation script returned error exit status 1
Processing triggers for initramfs-tools (0.120+deb8u2) ...
update-initramfs: Generating /boot/initrd.img-3.16.0-4-amd64
W: Possible missing firmware /lib/firmware/tigon/tg3_tso5.bin for module tg3
W: Possible missing firmware /lib/firmware/tigon/tg3_tso.bin for module tg3
W: Possible missing firmware /lib/firmware/tigon/tg3.bin for module tg3
Errors were encountered while processing:
E: Sub-process /usr/bin/dpkg returned an error code (1)

Solusinya adalah menambahkan tag LSB di /etc/init.d/snapvault

# Provides: snapvault
# Required-Start:
# Required-Stop:
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Start snapvault scheduler service on bootup
# Description: Enable snapvault.

Proses upgrade dan instalasi lainnya dapat berjalan kembali.