Boot problem after an OS update

# apt-get update
...
# apt-get upgrade
...
Preparing to unpack .../pve-firewall_2.0-33_amd64.deb ...
Unpacking pve-firewall (2.0-33) over (2.0-22) ...
Preparing to unpack .../pve-libspice-server1_0.12.8-2_amd64.deb ...
Unpacking pve-libspice-server1 (0.12.8-2) over (0.12.5-2) ...
Preparing to unpack .../pve-qemu-kvm_2.7.1-4_amd64.deb ...
Unpacking pve-qemu-kvm (2.7.1-4) over (2.5-9) ...
Preparing to unpack .../spiceterm_2.0-2_amd64.deb ...
Unpacking spiceterm (2.0-2) over (2.0-1) ...
Processing triggers for man-db (2.7.0.2-5) ...
Processing triggers for mime-support (3.58) ...
Processing triggers for install-info (5.2.0.dfsg.1-6) ...
Processing triggers for systemd (215-17+deb8u6) ...
Processing triggers for pve-manager (4.1-22) ...
Job for pvedaemon.service failed. See 'systemctl status pvedaemon.service' and 'journalctl -xn' for details.
dpkg: error processing package pve-manager (--unpack):
subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
pve-manager
E: Sub-process /usr/bin/dpkg returned an error code (1)
# shutdown -r now
 
Proxmox must upgrade by:
# apt-get dist-upgrade

If you can choose boot to older kernel version, try it and
# apt-get update
# apt-get dist-upgrade

It's look like no initrd image generated for new kernel