Manual:UpdateSearchIndex.php

updateSearchIndex.php is a used for periodic off-peak updating of the search index for the 3>Special:Recentchanges|recently changed pages. If you need to rebuild the search index entirely, run  instead.

Invocation
php maintenance/updateSearchIndex.php [-s start-timestamp] [-e end-timestamp] [-p posfile] [-l locktime] [-q]

Write permissions
The script will write the end timestamp on the file specified by the   parameter, that will default to  . The script will fail if the user executing the command doesn't have permissions to write to that file. To prevent the error, specify a file with write permissions, or create the file yourself and give it the appropriate permissions.