$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages will be upgraded:
  ubuntu-docs
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/1,181 kB of archives.
After this operation, 633 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Reading changelogs...
(Reading database ... 631459 files and directories currently installed.)
Preparing to unpack .../ubuntu-docs_14.10.4_all.deb ...
Unpacking ubuntu-docs (14.10.4) over (14.04.4) ...
dpkg: error processing archive /var/cache/apt/archives/ubuntu-docs_14.10.4_all.deb (--unpack):
 unable to make backup symlink for `./usr/share/help/en_GB/ubuntu-help/net-wireless-adhoc.page': No space left on device
No apport report written because the error message indicates a disk full error
                                                                              Errors were encountered while processing:
 /var/cache/apt/archives/ubuntu-docs_14.10.4_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)



$ df
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/sdb5       53454332 46294724   4421184  92% /
none                   4        0         4   0% /sys/fs/cgroup
udev             3923836        4   3923832   1% /dev
tmpfs             786992     1508    785484   1% /run
none                5120        4      5116   1% /run/lock
none             3934944    20828   3914116   1% /run/shm
none              102400      128    102272   1% /run/user