$ sudo apt-get install mysql-server
[sudo] password for gcp02: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
  libdbd-mysql-perl mysql-client-5.5 mysql-server-5.5
Suggested packages:
  libterm-readkey-perl tinyca
The following NEW packages will be installed:
  libdbd-mysql-perl mysql-client-5.5 mysql-server mysql-server-5.5
0 upgraded, 4 newly installed, 0 to remove and 83 not upgraded.
Need to get 0 B/4,041 kB of archives.
After this operation, 70.7 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
WARNING: The following packages cannot be authenticated!
  mysql-client-5.5 mysql-server-5.5 mysql-server
Install these packages without verification? [y/N] y
Preconfiguring packages ...
Selecting previously unselected package libdbd-mysql-perl.
(Reading database ... 342072 files and directories currently installed.)
Preparing to unpack .../libdbd-mysql-perl_4.025-1_amd64.deb ...
Unpacking libdbd-mysql-perl (4.025-1) ...
Preparing to unpack .../mysql-client-5.5_5.5.47-0+deb7u1_amd64.deb ...
Unpacking mysql-client-5.5 (5.5.47-0+deb7u1) ...
dpkg: error processing archive /var/cache/apt/archives/mysql-client-5.5_5.5.47-0+deb7u1_amd64.deb (--unpack):
 trying to overwrite '/usr/share/man/man1/mysql.1.gz', which is also in package mysql-client-core-5.5 5.5.47-0ubuntu0.14.04.1
dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
Selecting previously unselected package mysql-server-5.5.
Preparing to unpack .../mysql-server-5.5_5.5.47-0+deb7u1_amd64.deb ...
Unpacking mysql-server-5.5 (5.5.47-0+deb7u1) ...
Selecting previously unselected package mysql-server.
Preparing to unpack .../mysql-server_5.5.47-0+deb7u1_all.deb ...
Unpacking mysql-server (5.5.47-0+deb7u1) ...
Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
Processing triggers for ureadahead (0.100.0-16) ...
Errors were encountered while processing:
 /var/cache/apt/archives/mysql-client-5.5_5.5.47-0+deb7u1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)