I have linux ubuntu 16.04
and running MSSQL Server express
Service is up and running.

```
sudo systemctl status mssql-server

```

result

```
mssql-server.service - Microsoft SQL Server Database Engine
   Loaded: loaded (/lib/systemd/system/mssql-server.service; enabled; vendor pre
   Active: active (running) since Fri 2020-11-06 08:11:42 GMT; 2h 0min ago
     Docs: https://docs.microsoft.com/en-us/sql/linux
 Main PID: 961 (sqlservr)
   CGroup: /system.slice/mssql-server.service
           ├─ 961 /opt/mssql/bin/sqlservr
           └─1608 /opt/mssql/bin/sqlservr

```

I opened in terminal this path:

```
/opt/mssql-tools/bin$

```

I entered the path to access but

/opt/mssql-tools/bin$

```
sqlcmd -s SQLEXPRESS -u SA (Here password)

```

but i did not get anything, only this:

```
Sqlcmd: 'SA': Unexpected argument. Enter '-?' for help.

```

Long time ago i did not connect so i may have forgotten the creds>. So now my question are:

How to find the credentials (Username but especially SQL Server name? ) in the system?
Are they stored in any conf file apart MSSQL.CONF where i did not find them?
Is there a way to get them from the terminal?
IF they are not wrong, what is wrong, then>? Why i got that errors? I Was able to connect around 2 months ago.

Thanks to everyone.

Paolo