Comment 1 for bug 1407613

This is true. without setting DBPASS in above case, while installing percona-server, it will ask for password. But if we set above things , without prompting for root password it will install percona server. This should be documented.

root@desktop:/var/lib/mysql# DBPASS="root"
root@desktop:/var/lib/mysql# echo $DBPASS
root
root@desktop:/var/lib/mysql#
root@desktop:/var/lib/mysql# echo percona-server-server-5.6 percona-server-server/root_password password $DBPASS | debconf-set-selections
root@desktop:/var/lib/mysql# echo percona-server-server-5.6 percona-server-server/root_password_again password $DBPASS | debconf-set-selections
root@desktop:/var/lib/mysql#
root@desktop:/var/lib/mysql# sudo apt-get install percona-server-server-5.6 percona-server-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  tinyca
The following NEW packages will be installed:
  percona-server-server percona-server-server-5.6
0 upgraded, 2 newly installed, 0 to remove and 1 not upgraded.
Need to get 0 B/12.0 MB of archives.
After this operation, 94.6 MB of additional disk space will be used.
Preconfiguring packages ...
Selecting previously unselected package percona-server-server-5.6.
(Reading database ... 206198 files and directories currently installed.)
Preparing to unpack .../percona-server-server-5.6_5.6.21-70.1-698.utopic_amd64.deb ...
Unpacking percona-server-server-5.6 (5.6.21-70.1-698.utopic) ...
Selecting previously unselected package percona-server-server.
Preparing to unpack .../percona-server-server_5.6.21-70.1-698.utopic_amd64.deb ...
Unpacking percona-server-server (5.6.21-70.1-698.utopic) ...
Processing triggers for ureadahead (0.100.0-16) ...
Processing triggers for man-db (2.7.0.2-2) ...
Setting up percona-server-server-5.6 (5.6.21-70.1-698.utopic) ...
 * Stopping MySQL (Percona Server) mysqld [ OK ]
2015-01-06 13:50:18 0 [Warning] Using unique option prefix key_buffer instead of key_buffer_size is deprecated and will be removed in a future release. Please use the full name instead.
2015-01-06 13:50:18 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).

 * Percona Server is distributed with several useful UDF (User Defined Function) from Percona Toolkit.
 * Run the following commands to create these functions:

 mysql -e "CREATE FUNCTION fnv1a_64 RETURNS INTEGER SONAME 'libfnv1a_udf.so'"
 mysql -e "CREATE FUNCTION fnv_64 RETURNS INTEGER SONAME 'libfnv_udf.so'"
 mysql -e "CREATE FUNCTION murmur_hash RETURNS INTEGER SONAME 'libmurmur_udf.so'"

 * See http://www.percona.com/doc/percona-server/5.6/management/udf_percona_toolkit.html for more details

 * Starting MySQL (Percona Server) database server mysqld [ OK ]
 * Checking for corrupt, not cleanly closed and upgrade needing tables.
Setting up percona-server-server (5.6.21-70.1-698.utopic) ...
root@desktop:/var/lib/mysql#