Mongoexport auth error using mechanism "SCRAM-SHA-1" - mongodb

Question

I have taken over undocumented Mongo 4.4.8 cluster (PSA). I am trying to tidy it up and test thouroughly.
An original connection string:
MONGODB_URI=mongodb://${USER}:${PASS}#10.0.0.3:27017,10.0.0.6:27017,10.0.0.2:27017/bud?replicaSet=bud-replica&authSource=admin
I have enabled localhost and socket connection. I can log in from cmdline with
mongo -u ${USER} -p ${PASS}
MongoDB shell version v4.4.8
connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("492e331b-417e-458a-83c7-9db6eaae0869") }
MongoDB server version: 4.4.8
I can switch db to bud and perform the queries. But if I run just
mongo
then the authentication with the same credentials does not work:
bud-replica:PRIMARY> db.auth('admin','admin');
Error: Authentication failed.
0
I tried to search for users but shows there arent any:
bud-replica:PRIMARY> db.getUsers()
[ ]
bud-replica:PRIMARY> use bud
switched to db bud
bud-replica:PRIMARY> db.getUsers()
[ ]
This is mongod.conf security part:
security:
authorization: enabled
keyFile: "/etc/bud-rs"
Finally I need to export my data before doing experiments. Though the cmd line interface looks similar, mongoexport cannot fetch the data, regardless I set user/password or skip these arguments.
mongoexport -h localhost --db=bud -u ${USER} -p ${PASS} -c=accidents --jsonArray > accidents.json
2021-08-25T19:30:30.631+0200 could not connect to server: connection() error occured during connection handshake: auth error: sasl conversation error: unable to authenticate using mechanism "SCRAM-SHA-1": (AuthenticationFailed) Authentication failed.
mongoexport -h localhost --db=bud -u ${USER} -p ${PASS} -c=accidents --jsonArray --authenticationDatabase “admin” > accidents.json
2021-08-25T19:36:18.738+0200 could not connect to server: connection() error occured during connection handshake: auth error: sasl conversation error: unable to authenticate using mechanism "SCRAM-SHA-1": (AuthenticationFailed) Authentication failed.
root#10:~# mongoexport -h localhost --db=bud -u ${USER} -p ${PASS} -c=accidents --jsonArray --authenticationDatabase “bud” > accidents.json
2021-08-25T19:38:21.174+0200 could not connect to server: connection() error occured during connection handshake: auth error: sasl conversation error: unable to authenticate using mechanism "SCRAM-SHA-1": (AuthenticationFailed) Authentication failed.
I am really confused and I failed to find a solution on Google or SO.
Second relevant question:
If I need to create new user, shall I do it on all replicas or it is automatically synchronized?
1st update
This is the workaround, but my questions are still valid. I want to understand.
root#10:~# mongoexport --db=bud -u ${USER} -p ${PASS} -c=accidents --jsonArray "mongodb://admin:admin#10.0.0.3:27017/bud?authSource=admin" > accidents.json
2021-08-25T20:46:54.777+0200 connected to: mongodb://[**REDACTED**]#10.0.0.3:27017/bud?authSource=admin
2021-08-25T20:46:55.778+0200 [........................] bud.accidents 0/4379 (0.0%)
2021-08-25T20:46:56.497+0200 [########################] bud.accidents 4379/4379 (100.0%)
2021-08-25T20:46:56.497+0200 exported 4379 records
2nd update
bud-replica:PRIMARY> use admin
bud-replica:PRIMARY> show collections
system.keys
system.users
system.version
bud-replica:PRIMARY> db.system.users.find()
{ "_id" : "admin.admin", "userId" : UUID("769e4f5c-6f46-4153-857e-47d7d8730066"), "user" : "admin", "db" : "admin", "credentials" : { "SCRAM-SHA-1" : { "iterationCount" : 10000, "salt" : "32/AP4019eome36j8n

Answer 1

The user credential was created in the admin database.
When connecting with the mongo shell, switch with use admin before running db.auth
The mongoexport command that worked used authSource=admin in the connection string.
Add --authenticationDatabase=admin to the other command line to direct it to use the admin database for auth as well.

Answer 2

whole example command as below worked for me.
Mongodb version: 5.x.x, also for Mongodb version: 8.x.x
mongodump --authenticationDatabase=admin --uri mongodb://username:password#mongodb-host/db-name?ssl=false&authSource=admin