backup fail:Cannot find the password file

Yesterday, I wanted to backup the full database  under vertica-7.1.1community version.

I did what the guid said, using vbr.py --setupconfig  command step by step.

Both of the db.ini,pwd file  was under the "/home/vertica" directory.

The content of the db.ini was as below:

**************************************************************************
[Misc]snapshotName = db
restorePointLimit = 1
passwordFile = pwd

[Database]
dbName = db_vertica_test
dbUser = vertica

[Transmission]

[Mapping]
v_db_vertica_test_node0001 = vertica01:/home/vertica/backup
v_db_vertica_test_node0002 = vertica02:/home/vertica/backup

**************************************************************************




The content of the pwd file was as below:

**************************************************************************
dbPassword = vertica
**************************************************************************


Then , run the command "/opt/vertica/bin/vbr.py --task backup --config-file db.ini":



It's my pleasure to get your help to know why this error occurred and the solution.