The following packages will be REMOVED:
  omd-1.20*
0 upgraded, 0 newly installed, 1 to remove and 527 not upgraded.
24 not fully installed or removed.
After this operation, 309 MB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 182941 files and directories currently installed.)
Removing omd-1.20 (0.precise) ...
Stopping all OMD monitoring sites using omd version 1.20:
update-alternatives: error: /var/lib/dpkg/alternatives/omd corrupt: slave link same as main link /usr/bin/omd
dpkg: error processing package omd-1.20 (--purge):
 subprocess installed pre-removal script returned error exit status 2
Errors were encountered while processing:
 omd-1.20
E: Sub-process /usr/bin/dpkg returned an error code (1)