Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
  libdbd-mysql-perl libdbi-perl libmysqlclient18 libterm-readkey-perl
  mysql-client-5.5 mysql-client-core-5.5 mysql-common mysql-server-5.5
  mysql-server-core-5.5
Suggested packages:
  libmldbm-perl libnet-daemon-perl libplrpc-perl libsql-statement-perl tinyca
  mailx
The following NEW packages will be installed
  libdbd-mysql-perl libdbi-perl libmysqlclient18 libterm-readkey-perl
  mysql-client-5.5 mysql-client-core-5.5 mysql-common mysql-server
  mysql-server-5.5 mysql-server-core-5.5
0 to upgrade, 10 to newly install, 0 to remove and 8 not to upgrade.
Need to get 0 B/8,939 kB of archives.
After this operation, 96.2 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Preconfiguring packages ...
Selecting previously unselected package mysql-common.
(Reading database ... 255014 files and directories currently installed.)
Preparing to unpack .../mysql-common_5.5.38-0ubuntu0.14.04.1_all.deb ...
Unpacking mysql-common (5.5.38-0ubuntu0.14.04.1) ...
Selecting previously unselected package libmysqlclient18:amd64.
Preparing to unpack .../libmysqlclient18_5.5.38-0ubuntu0.14.04.1_amd64.deb ...
Unpacking libmysqlclient18:amd64 (5.5.38-0ubuntu0.14.04.1) ...
Selecting previously unselected package libdbi-perl.
Preparing to unpack .../libdbi-perl_1.630-1_amd64.deb ...
Unpacking libdbi-perl (1.630-1) ...
Selecting previously unselected package libdbd-mysql-perl.
Preparing to unpack .../libdbd-mysql-perl_4.025-1_amd64.deb ...
Unpacking libdbd-mysql-perl (4.025-1) ...
Selecting previously unselected package libterm-readkey-perl.
Preparing to unpack .../libterm-readkey-perl_2.31-1_amd64.deb ...
Unpacking libterm-readkey-perl (2.31-1) ...
Selecting previously unselected package mysql-client-core-5.5.
Preparing to unpack .../mysql-client-core-5.5_5.5.38-0ubuntu0.14.04.1_amd64.deb ...
Unpacking mysql-client-core-5.5 (5.5.38-0ubuntu0.14.04.1) ...
Selecting previously unselected package mysql-client-5.5.
Preparing to unpack .../mysql-client-5.5_5.5.38-0ubuntu0.14.04.1_amd64.deb ...
Unpacking mysql-client-5.5 (5.5.38-0ubuntu0.14.04.1) ...
Selecting previously unselected package mysql-server-core-5.5.
Preparing to unpack .../mysql-server-core-5.5_5.5.38-0ubuntu0.14.04.1_amd64.deb ...
Unpacking mysql-server-core-5.5 (5.5.38-0ubuntu0.14.04.1) ...
Processing triggers for man-db (2.6.7.1-1) ...
Setting up mysql-common (5.5.38-0ubuntu0.14.04.1) ...
(Reading database ... 255366 files and directories currently installed.)
Preparing to unpack .../mysql-server-5.5_5.5.38-0ubuntu0.14.04.1_amd64.deb ...
Aborting downgrade from (at least) 10.0 to 5.5.
If are sure you want to downgrade to 5.5, remove the file
/var/lib/mysql/debian-*.flag and try installing again.
dpkg: error processing archive /var/cache/apt/archives/mysql-server-5.5_5.5.38-0ubuntu0.14.04.1_amd64.deb (--unpack):
 subprocess new pre-installation script returned error exit status 1
Selecting previously unselected package mysql-server.
Preparing to unpack .../mysql-server_5.5.38-0ubuntu0.14.04.1_all.deb ...
Unpacking mysql-server (5.5.38-0ubuntu0.14.04.1) ...
Errors were encountered while processing:
 /var/cache/apt/archives/mysql-server-5.5_5.5.38-0ubuntu0.14.04.1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)