Xtrabackup crash

innobackupex: Error: The xtrabackup child process has died at /usr/local/bin/innobackupex line 2703.
ls: -t: No such file or directory
grep: /usr/backup/mysql//incr/**/backup.chain: No such file or directory

Are you sure the directories are present? can you provide output of ls -laR /usr/backup/mysql ?