Linux Samba server and Linux Samba client tutorial

I want to share from the server a directory, and use that directory share on the client computer. Using the Microsoft Windows "Server Message Block" (SMB)/CIFS directory sharing protocol.
I have created two Kubuntu 26.04 virtual machines: a Samba server and a Samba client.

Samba server: 192.168.122.202. Computer name: ASERVER. User name: sadmin.
Samba client: 192.168.122.92. Username: administrator.

A video version of this tutorial is available https://www.youtube.com/watch?v=mNgBZtunNnE .

1.Configure the Samba server computer

Kubuntu 26.04 by default uses the ufw firewall solution and ufw is disabled. Configuring a firewall is another topic.
Create the directory /home/sadmin/smbshare . Put some files there.

# Become the user root.
sudo su
ufw status
# Says "Status: inactive".
apt update
apt install samba smbclient
cat << 'EOF' >> /etc/samba/smb.conf

[linux_smbshare]
   comment = Linux smbshare
   path = /home/sadmin/smbshare
   browseable = yes
   read only = no
   guest ok = no
   valid users = sadmin
   create mask = 0660
   directory mask = 0770
EOF
testparm
systemctl restart smbd
smbpasswd -a sadmin
# I use the same password for the user sadmin. Both for the
# Linux user account and for the Samba user account.
pdbedit -L
# Stop being the user root.
exit
smbclient //localhost/linux_smbshare -U sadmin
ls
# Exit smbclient shell/REPL.
exit

Note that two parts of NETBIOS protocol are disabled by default: the one similar to DNS (hostname to IPv4 conversion) and the one where the Samba server advertises itself on the Local Area Network (LAN) as an SMB server.

testparm
says:
[global]
        disable netbios = Yes

Bonus points if the Samba server computer has an IPv4 address that does not change.
Restart the Samba server computer.

2.Configure the Samba client computer

sudo apt update
sudo install smbclient cifs-utils avahi-utils

The information that, years ago, we could get using the NETBIOS protocol can now be accessed from a Samba client computer using other technologies:

* When listing SMB servers on the LAN. Instead of using NETBIOS. We can use the DNS-Based Service Discovery (DNS-SD) protocol (avahi).

$ smbtree -N
main: This is utility doesn't work if netbios name resolution is not configured.
If you are using SMB2 or SMB3, network browsing uses WSD/LLMNR, which is not yet supported by Samba.
SMB1 is disabled by default on the latest Windows versions for security reasons. \
It is still possible to access the Samba resources directly via \name or \ip.address.

$ avahi-browse -rtp _smb._tcp
+;virbr0;IPv4;ASERVER;Microsoft Windows Network;local
=;virbr0;IPv4;ASERVER;Microsoft Windows Network;local;aserver.local;192.168.122.202;445;

* Converting from "ASERVER" to an IPv4 address does not work. Converting from "ASERVER.local" to the IPv4 address 192.168.122.202 works because of avahi DNS-SD DNS server/client, mdns4_minimal.

$ ping ASERVER
ping: ASERVER: Temporary failure in name resolution
$ ping ASERVER.local
PING ASERVER.local (192.168.122.202) 56(84) bytes of data.
64 bytes from 192.168.122.202: icmp_seq=1 ttl=64 time=0.110 ms
$ cat /etc/nsswitch.conf | grep hosts
hosts:          files mdns4_minimal [NOTFOUND=return] mymachines dns

# Continue configuring the Samba client.
sudo mkdir -p /media/192_168_122_202_linux_smbshare
# Without file with SMB username and password.
sudo mount -t cifs //192.168.122.202/linux_smbshare /media/192_168_122_202_linux_smbshare \
-o username=sadmin,uid=administrator,gid=administrator
sudo umount /media/192_168_122_202_linux_smbshare

# With file with SMB username and password.
# As the user administrator.
cat << 'EOF' > /home/administrator/.smbcredentials
username=sadmin
password=pass123
EOF

sudo mount -t cifs //192.168.122.202/linux_smbshare /media/192_168_122_202_linux_smbshare \
-o uid=administrator,gid=administrator,credentials=/home/administrator/.smbcredentials

sudo mount /media/192_168_122_202_linux_smbshare
sudo umount /media/192_168_122_202_linux_smbshare

Append to /etc/fstab the line:

//192.168.122.202/linux_smbshare /media/192_168_122_202_linux_smbshare cifs noauto,uid=administrator,gid=administrator,credentials=/home/administrator/.smbcredentials 0 0

Note that "//192.168.122.202/linux_smbshare" will not be mounted automatically because of "noauto" in /etc/fstab.
Each time you reboot your Samba client computer and want to use the shared directory, run:

sudo mount /media/192_168_122_202_linux_smbshare

Advantages: if the Samba server is down or configured incorrectly or if the network connection between Samba server computer and Samba client computer is not great. The Samba client computer will not be affected.

3.I test the KDE app smb4k

https://apps.kde.org/smb4k is a KDE GUI app that acts as an SMB client. It can list SMB servers available on the LAN. It can determine the "SMB domain" of a computer. It can get the list of shared directories. It can list the contents of shared directories. It can mount a shared directory using "mount.cifs".

kde-builder smb4k
kde-builder --run smb4k

I have encountered some issues:

A. If server is Kubuntu 26.04, smb4k cannot get the list of shares of the SMB server. https://invent.kde.org/network/smb4k/-/merge_requests/24
This is because "ping ASERVER" does not work, but "ping ASERVER.local" works correctly.

B. In smb4k when hovering on top of a SMB server, a tooltip is shown that says "Workgroup: LOCAL" instead of "Domain: WORKGROUP".
From the command line, we can get the correct "SMB domain" for an SMB server:

$ rpcclient -U % -c "lsaquery" 192.168.122.202
Domain Name: WORKGROUP
Domain Sid: (NULL SID)

A fix for this issue is more complicated because each time dnssd/kdnssd notifies smb4k that an SMB server named A exists on the LAN. smb4k should decide if this computer was received previously. If not, smb4k should run the command line above and get the "actualDomain" from the STDOUT of the process. Bonus points if getting the correct SMB domain is non blocking, creates at most 5 "rpcclient" sub processes at the same time.