Mounting my ReadyNAS from Nautilus stopped working after upgrading to Ubuntu 20.04. Turns out there was a change in behavior in Sambva v4.11 that disabled SMB1 protocol by default. It’ll be interesting to see how this pans out in the rest of the Linux community … fortunately there’s a workaround!

Update: same on Debian 11 (bullseye) and Linux Mint 20 (Ulyana)

The fix, from AskUbuntu and Reddit, suggest lowering the min protocol version. To do this, open /etc/samba/smb.conf with your favorite editor:

sudo mg /etc/samba/smb.conf

Add the following line to the [global] section:

client min protocol = NT1

If you’re using Nautilus (Files, Nemo), you’re done. But if you’re using Samba, e.g. from the command line, restart it to make change take effect:

sudo systemctl restart smbd.service

That’s it. If it doesn’t work, you could try setting an ever lower protocol version:

client min protocol = CORE

For me, however, using NT1 makes everything work. Including renaming files and such, which does not work with CORE.