Urgent, error on cbbackup in ubuntu 14!

I can not do backup to my db i am stack for 3 days.

When i type the command:
sh cbbackup http://127.0.0.1:8091 /backups -u admin -p password
or
sh cbbackup -u admin -p password http://localhost:8091 /backups

i get error:
“Error: please provide both a source and a backup_dir”

It working good on mac but not on ubuntu 14.