I am trying to install the cloud manager by this process
http://www.cloudera.com/documentation/manager/5-1-x/Cloudera-Manager-Installation-Guide/cm5ig_instal...
but getting this error

Log file:
/var/log/cloudera-manager-installer/3.install-oracle-j2sdk1.7.log
----------------------------------
Reading package lists...
Building dependency tree...
Reading state information...
The following NEW packages will be installed:
oracle-j2sdk1.7
0 upgraded, 1 newly installed, 0 to remove and 188 not upgraded.
Need to get 142 MB of archives.
After this operation, 292 MB of additional disk space will be used.
WARNING: The following packages cannot be authenticated!
oracle-j2sdk1.7
E: There are problems and -y was used without --force-yes
Server Information:
Distributor ID: Ubuntu
Description: Ubuntu 14.04.5 LTS
Release: 14.04
Codename: trusty