$ sudo apt-get install smartmontools
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  bsd-mailx liblockfile-bin liblockfile1 postfix
Suggested packages:
  procmail postfix-mysql postfix-pgsql postfix-ldap postfix-pcre sasl2-bin
  dovecot-common postfix-cdb postfix-doc gsmartcontrol smart-notifier
The following NEW packages will be installed:
  bsd-mailx liblockfile-bin liblockfile1 postfix smartmontools
0 upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
Need to get 1,677 kB of archives.
After this operation, 5,683 kB of additional disk space will be used.
Do you want to continue? [Y/n] 
Get:1 http://archive.ubuntu.com/ubuntu xenial/main amd64 liblockfile-bin amd64 1.09-6ubuntu1 [10.8 kB]
Get:2 http://archive.ubuntu.com/ubuntu xenial/main amd64 liblockfile1 amd64 1.09-6ubuntu1 [8,056 B]
Get:3 http://archive.ubuntu.com/ubuntu xenial/main amd64 postfix amd64 3.1.0-3 [1,152 kB]
Get:4 http://archive.ubuntu.com/ubuntu xenial/main amd64 bsd-mailx amd64 8.1.2-0.20160123cvs-2 [63.7 kB]
Get:5 http://archive.ubuntu.com/ubuntu xenial/main amd64 smartmontools amd64 6.4+svn4214-1 [442 kB]
Fetched 1,677 kB in 2s (782 kB/s)    
debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable
Selecting previously unselected package liblockfile-bin.
(Reading database ... 191931 files and directories currently installed.)
Preparing to unpack .../liblockfile-bin_1.09-6ubuntu1_amd64.deb ...
Unpacking liblockfile-bin (1.09-6ubuntu1) ...
Selecting previously unselected package liblockfile1:amd64.
Preparing to unpack .../liblockfile1_1.09-6ubuntu1_amd64.deb ...
Unpacking liblockfile1:amd64 (1.09-6ubuntu1) ...
Selecting previously unselected package postfix.
Preparing to unpack .../postfix_3.1.0-3_amd64.deb ...
debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable
dpkg: error processing archive /var/cache/apt/archives/postfix_3.1.0-3_amd64.deb (--unpack):
 subprocess new pre-installation script returned error exit status 1
Selecting previously unselected package bsd-mailx.
Preparing to unpack .../bsd-mailx_8.1.2-0.20160123cvs-2_amd64.deb ...
Unpacking bsd-mailx (8.1.2-0.20160123cvs-2) ...
Selecting previously unselected package smartmontools.
Preparing to unpack .../smartmontools_6.4+svn4214-1_amd64.deb ...
Unpacking smartmontools (6.4+svn4214-1) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for libc-bin (2.23-0ubuntu3) ...
Processing triggers for systemd (229-4ubuntu7) ...
Processing triggers for ureadahead (0.100.0-19) ...
Errors were encountered while processing:
 /var/cache/apt/archives/postfix_3.1.0-3_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)