Preparing to unpack .../base-files_9.4ubuntu4.3_amd64.deb ...
Unpacking base-files (9.4ubuntu4.3) over (9.4ubuntu4.2) ...
Processing triggers for plymouth-theme-ubuntu-text (0.9.2-3ubuntu13.1) ...
update-initramfs: deferring update (trigger activated)
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for install-info (6.1.0.dfsg.1-5) ...
Processing triggers for cracklib-runtime (2.9.2-1build2) ...
Processing triggers for initramfs-tools (0.122ubuntu8.1) ...
update-initramfs: Generating /boot/initrd.img-4.4.0-31-generic
cryptsetup: WARNING: failed to detect canonical device of overlay
cryptsetup: WARNING: could not determine root device from /etc/fstab
cp: cannot create regular file '/cdrom/casper/initrd.gz.new': No such file or directory