Comment 1 for bug 1376748

xtrabackup_binlog_pos_innodb is created on prepare. There's apparently some attempt in the manual to explain this, but it could use better wording:

"You can find the binary log position corresponding to a backup performing the --prepare process. If your backup is from a server with binary logging enabled, xtrabackup will create a file named xtrabackup_binlog_info in the target directory."

Let's keep it as a doc request to improve the manual, i.e. make it clear the xtrabackup_binlog_pos_innodb is created as a result of the prepare process, not the backup one.