I believe the command your looking for is pdbedit.

From the man page "pdbedit - manage the SAM database (Database of Samba Users)"

sudo pdbedit -L -v

-L to list users. -v to be verbose.

If you login to the Samba server, you can run the following command to list valid Samba users:

sudo pdbedit -L -v

The above command will list users known to Samba - this is not the same as the users and passwords known the Linux server it is running on. Read that last sentence again.

If you don't know the passwords for the old users, you have a couple of choices:

• change the password of an old, existing user to something new, or
• add a new user with a new password that you can use.

I think the first option is less desirable because it means if there are clients that know the old password and you change it, they will suddenly stop working.

So, I would add a new Samba user. This new user must have a login name on the Samba server, so either choose an existing Linux username you want to use, or add a new one. Here's a way to add a user called samba:

• add samba as a regular user with a regular Linux login
• add samba as a Samba user
• set the Samba password for samba
• use those credentials when mounting a Samba share

That looks like:

sudo adduser samba         # add a regular Linux user 
sudo smbpasswd -a samba    # add Samba user called `samba`
sudo smbpasswd -e samba    # enable - may not be needed

Now you should be able to mount the shares with username=samba and the password you just set.

Try smbclient -L ip_of_net_interface -U your_user_name. This option allows you to look at what services are available on a server. You use it as smbclient -L host and a list should appear.

A samba user is a normal Ubuntu user that you create and then use to set up samba with. Samba has its own password program called "smbpasswd" with ...

smbpasswd -a {user}

That gives access to /home/{user}/

/etc/samba/smb.conf also lets you set a share for that samba user

[accounts]
comment = Accounts data directory
path = /directory/dir/
valid users = {user}
public = no
writable = yes

That last one makes files writable.

Have a look at this guide, it is a little bit old but the core concept amd functioality still applies, it may give you a better idea and undestanding about user creation, permissions and sharing directories in general

https://www.digitalocean.com/community/tutorials/how-to-set-up-a-samba-share-for-a-small-organization-on-ubuntu-16-04

hope it helps! :)