sudo aptitude reinstall initramfs-tools
The following packages will be REINSTALLED:
  initramfs-tools 
0 packages upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded.
Need to get 8,602 B of archives. After unpacking 0 B will be used.
Get: 1 http://es.archive.ubuntu.com/ubuntu xenial-updates/main i386 initramfs-tools all 0.122ubuntu8.1 [8,602 B]
Fetched 8,602 B in 0s (40.5 kB/s)    
(Reading database ... 152116 files and directories currently installed.)
Preparing to unpack .../initramfs-tools_0.122ubuntu8.1_all.deb ...
Unpacking initramfs-tools (0.122ubuntu8.1) over (0.122ubuntu8.1) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up initramfs-tools (0.122ubuntu8.1) ...
update-initramfs: deferring update (trigger activated)
Processing triggers for initramfs-tools (0.122ubuntu8.1) ...
update-initramfs: Generating /boot/initrd.img-4.4.0-38-generic
mktemp: failed to create directory via template ‘/var/tmp/mkinitramfs_XXXXXX’: No such file or directory
update-initramfs: failed for /boot/initrd.img-4.4.0-38-generic with 1.
dpkg: error processing package initramfs-tools (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 initramfs-tools
E: Sub-process /usr/bin/dpkg returned an error code (1)
Failed to perform requested operation on package.  Trying to recover:
Setting up initramfs-tools (0.122ubuntu8.1) ...
update-initramfs: deferring update (trigger activated)
Processing triggers for initramfs-tools (0.122ubuntu8.1) ...
update-initramfs: Generating /boot/initrd.img-4.4.0-38-generic
mktemp: failed to create directory via template ‘/var/tmp/mkinitramfs_XXXXXX’: No such file or directory
update-initramfs: failed for /boot/initrd.img-4.4.0-38-generic with 1.
dpkg: error processing package initramfs-tools (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 initramfs-tools