innobackupex unexpectedly ending while creating backup

I’m starting backup to remote server using innobackupex:
innobackupex --defaults-file=/etc/mysql/mysqld-2.cnf --slave-info --user=bck_user --password=bck_password --socket=/var/run/mysqld/mysqld-2.sock --stream=xbstream /database/| ssh -o StrictHostKeyChecking=no -c arcfour ‘xbstream -x -C /database/db1/’

after some time got:

log scanned up to (16773756142840)
log scanned up to (16773756264665)
print() on closed filehandle XTRABACKUP_PID at /usr/local/bin/innobackupex line 2645.
140611 07:48:26 innobackupex: Waiting for ibbackup (pid=7957) to finish

that’s it
using percona-xtrabackup-2.1.9-744-Linux-x86_64.tar.gz

Could you check tmpdir in /etc/mysql/mysqld-2.cnf? It looks like the program failed to create a pid file under that directory. Please make sure the user running innobackupex has privilege to write to tmpdir.