[Samba] Samba suddenly acting strangely

[Andrea Venturoli]

Hello.

I know my description of the problem will be vague... I'm not asking for 
specific help, rather for some directions on where to look in order to 
understand it.

I've got several setups which are all alike:
_ FreeBSD (currently 13.2, 13.3 or, rarely, 14.0);
_ ZFS;
_ two jails: one for an AD DC and one for a member fileserver;
_ Samba <4.17 (in the past), 4.17 (still installed in some places) or 
4.19 (upgrading all instances is underway);
_ no use of ACLs.

This setup usually works fine.

However, from time to time, the fileserver starts acting stangely; most 
of the times this happened after either the DC or the FS was upgraded 
(e.g. from 4.17 to 4.19), but I also saw this all of a sudden without 
any apparent external reason.



Symptoms include one or more of the following:

_ intermittent "file not found" problem, when the file is there (e.g. 
run a program from a network share and it will complain some DLLs are 
missing; run it again and it might work);
_ directory listings missing some subdirectories or files, but moving to 
another directory and coming back might show everything;

_ inability to open any document (e.g. Word), but ability to copy the 
file to a local folder (and then use it properly);
_ Adobe Acrobat Reader hanging when opening a PDF file from a share;

_ ability to enter any root folder of a share, but no second level folders;

_ inability to list shares, i.e opening "\\fileserver", running "NET 
VIEW \\fileserver" or "smbclient -L //fileserver" hanging



I was always able to solve (although not necessarily at first try) by 
doing one or both of:
_ removing DOSATTRIB extended attribute from all files/directories;
_ wiping Samba's databases, starting from scratch and rejoining the domain.



Unfortunately I wasn't able to save some useful logs yet, but I think I 
saw two strange things:
_ when a client tried accessing some file and failed, the logs were 
populated with entries about other files (possibly in other shares) 
which no one was attempting to access at that time;
_ I'm not sure about this, but I think sometimes Samba mistook files for 
folders or vice-versa.



I'm very ignorant about Samba's internals, but one possible explanation 
I came up with is that Samba has some sort of database about 
files/folders and for some reason it started misapplying it (i.e. apply 
the wrong record of the database to a file/folder).
Does this make any sense? Does this sort of database/cache/whatever exist?



Altough everything is working now on all the systems I manage, it 
already happened at least five times (on at least three different 
networks), so I'd like to be ready in case it happens again.

Any hint appreciated.

  bye & Thanks
	av.