How to debug NT_STATUS_IO_TIMEOUT?

Question

When trying to access a samba share with smblcient -L //localhost from my local Samba Server, I get after a delay the error message

protocol negotiation failed: NT_STATUS_IO_TIMEOUT

What are the debugging steps to get to the root of this problem systematically?

Background:

For my own training purposes I am setting up a simple shared folder over a samba server on a CentOS 7 virtual machine.

I added following lines to the smb.conf file and created the directory, selinux configuration and firewall rule.

[sambashare]
comment = sambashare
path = /sambashare
public = yes
writable = yes
write list = +users

Answer 1

Solution:

You haven't configured DNS name resolution for your servername and have to set the servername either in the /etc/hosts manually or in your DNS server.

Debug process:

In the case of NT_STATUS_IO_TIMEOUT try to use a network traffic analyser like tcpdump. (ex. tcpdump -i >network interface<)

If following lines appear:

07:57:54.726390 IP 10.0.2.9.39939 > 10.0.2.1.domain: 20986+ A? server.example.local. (38)
07:57:54.726648 IP 10.0.2.9.39939 > 10.0.2.1.domain: 44015+ AAAA? server.example.local. (38)
07:57:54.727069 IP 10.0.2.9.48743 > 10.0.2.1.domain: 34381+ PTR? 1.2.0.10.in-addr.arpa. (39)
07:57:54.732388 IP 10.0.2.1.domain > 10.0.2.9.39939: 20986 NXDomain* 0/0/0 (38)
07:57:54.733400 IP 10.0.2.1.domain > 10.0.2.9.48743: 34381 NXDomain* 0/0/0 (39)
07:57:54.733642 IP 10.0.2.9.53191 > 10.0.2.1.domain: 24458+ PTR? 9.2.0.10.in-addr.arpa. (39)

This means that the smbclient isn't able to resolve the servername server.example.local which is a DNS resolution problem.

Answer 2

For me on Fedora Rawhide 33 I needed to use one the following in "/etc/samba/smb.conf":

client min protocol = CORE

or

client min protocol = NT1

and define the host in "/etc/hosts":

<ip_address>   REMOTE_DEVICE

Answer 3

I have added the following line in /etc/samba/smb.conf and it works :

guest ok  = yes

in the section of my share parameters.

Then I've restarted the service and it works perfectly