Disclaimer

The SMBv1 protocol is from the 1983, it is unsecure and thus disabled for a good reason. The SMBv2 protocol has been available since 2006.

Problem Description

I arrived at this question trying to find a solution for the following two problems:

1. I have an HP printer that can only use the legacy SMBv1 protocol (HP OfficeJet Pro 8620). So my printer refused to connect to the network share and the scan to network feature stopped working.

2. I tried to use Nautilus to browse the network shares on my own Ubuntu system. And I was getting an error with the message Unable to access location Failed to retrieve share list from server: Invalid Argument:

   

Solution

After several attempts with different values in the /etc/samba/smb.conf file I was finally able to resolve these problems using these two values:

client min protocol = NT1
server min protocol = NT1

I also found posts that suggested to add this third parameter:

ntlm auth = ntlmv1-permitted

However, on my system this was not necessary.

Explanation

As I understand it, the client min protocol option controls how your system communicates with other SMB servers, changing this option could be useful if your Ubuntu system works as a client and you want to use SMBv1 to access a server. By default (with Samba 4.11) your local Samba installation is configured to require SMBv2 or higher connections.

On the other hand, if your Ubuntu system acts as the server that requires SMBv2 or higher and you have a remote client (such as a printer) that can only understand the legacy SMBv1 protocol, then it seems that changing the client min protocol has no effect. Instead you need to change the server min protocol. This way the client can negotiate SMBv1 with the Samba daemon running on your Ubuntu system.

Side note, you can also pass the client min protocol option to tools such as smbclient, for example:

smbclient -L //<hostname>/<folder> --option='client min protocol=NT1'

Can be used to set the client protocol to SMBv1. This was useful to test the effect of changes in the smb.conf file.

I tried this on Ubuntu 20.04 which comes with samba version 4.11. I have not tested this solution on older Ubuntu distributions.

The smb-protocols nmap script checks to see which smb dialects are present on the Samba server.

client min protocol sets the minimum smb dialect that server can use to connect to another server not the minimum dialects that a client to this server can use.

By default the version of samba used in Ubuntu 18.04 sets the server min to NT1 ( smbv1 ) and the max to SMBv3.

If you want to restrict access to this server to SMB3 and SMB3 only you need to set the server min protocol:

server min protocol = SMB3

*Note: there are sub-variants to this dialect:

SMB3_00: Windows 8

SMB3_02: Windows 8.1

SMB3_10: early Windows 10

SMB3_11: Windows 10

By default SMB3 in smb.conf selects the SMB3_11 variant.*

First, there is no such thing as a HomeGroup in Linux, MacOS, or Windows starting with Win10.

Second, if you are talking about that specific error when running smbclient you would need to enable SMB1 ( Samba calls it NT1 ) on the client side in /etc/samba/smb.conf. Right under the workgroup = WORKGROUP line add this one:

client min protocol = NT1

Of course the server you are trying to connect to must have SMB1 enabled on its side. If you kept your Win10 machine up to date it is disabled so you will have to enable it there. If the server is running Ubuntu 20 or anything with the same version of samba you would have to edit smb.conf on that machine and add:

server min protocol = NT1

Then restart samba:

sudo service smbd restart
sudo service nmbd restart

If you don't do that on the server you will likely get a protocol negotiation failed: error.

That will probably eliminate the SMB1 error message. Whether you can "discover" all the workgroups and hosts in Nautilus is another matter. If you have to turn the clock back to SMB1 days you need to follow the rules set at that era ... name resolve order, host name length restrictions, etc ...

put in the [global] section of /etc/samba/smb.conf the directive

min protocol = NT1

samba calls SMB1 as NT1.

smb.conf doesn't actually come from the samba ( server ) package. It comes from samba-common since it has options that can control both client and server.

If youhave no need for a samba server on your system the best way to get smb.conf onto you system is to install smbclient:

sudo apt install smbclient

I would suggest removing the smb.conf file you created manually before you install smbclient.