www:/var/log# apt-get install postgresql-common
Reading package lists... Done
Building dependency tree... Done
The following NEW packages will be installed:
  postgresql-common
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 0B/87.1kB of archives.
After unpacking 316kB of additional disk space will be used.
Preconfiguring packages ...
postgresql-common failed to preconfigure, with exit status 1
(Reading database ... 38875 files and directories currently installed.)
Unpacking postgresql-common (from .../postgresql-common_57_all.deb) ...
dpkg: error processing /var/cache/apt/archives/postgresql-common_57_all.deb (--unpack):
 subprocess pre-installation script returned error exit status 1
Errors were encountered while processing:
 /var/cache/apt/archives/postgresql-common_57_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)