I try to create a backup of my MongoDB replicaset but I have an authentication problem :D .

So when I try to use mongodump

root@e03c2a89ac31:/# mongodump -u myBackupAccount -p 123456 --host mongo1 --out /home/backup
2017-01-17T11:00:41.069+0000    Failed: error connecting to db server: server returned error on SASL authentication step: Authentication failed.
root@e03c2a89ac31:/# mongodump -u myBackupAccount -p 123456 --host mongo1 --authenticationDatabase admin --out /home/backup
2017-01-17T12:37:45.819+0000    Failed: error connecting to db server: server returned error on SASL authentication step: Authentication failed.

But if I try with a mongo shell, I can connect to my instance

root@e03c2a89ac31:/# mongo -u myBackupAccount -p 123456 --host mongo1
MongoDB shell version v3.4.1
connecting to: mongodb://mongo1:27017/
MongoDB server version: 3.4.1
REPLICASET_NAME:PRIMARY> exit

My backup user was created with that command

root@e03c2a89ac31:/# mongo -u myUserAdmin --authenticationDatabase "admin" -p 123456
MongoDB shell version v3.4.1
connecting to: mongodb://mongo1:27017/
MongoDB server version: 3.4.1
REPLICASET_NAME:PRIMARY> db.createUser({user: "myBackupAccount", pwd: "123456", roles: [ { role: "backup", db: "admin" } ]})

So do you know why it isn't working ? I did somethings bad ? :p

Thanks in advance for your help ;)