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Go into the directory where the core file is located (this is version 6.6.0), stop solr, run the repair command and finally start solr again:
cd /opt/solr-6.6.0/server/solr-webapp/webapp/WEB-INF/lib/ invoke-rc.d solr stop java -cp lucene-core-6.6.0.jar -ea:org.apache.lucene... org.apache.lucene.index.CheckIndex "/var/solr/data/dovecot/data/index" -exorcise invoke-rc.d solr start
Note that “-ea:org.apache.lucene…” is the literal value of the parameter.