[Samba] linux-to-linux samba weird problem

Neal Murphy neal.p.murphy at alum.wpi.edu
Wed Feb 27 14:00:23 MST 2013

I've a weird problem with Samba. I'm using Samba to share a filesystem between 
two linux systems because I believe I need byte range locking to prevent 
multiple processes on different computers from reading/writing the same ISAM 

I have a Debian wheezy file server running Samba; no domain controller, just a 
simple, single share. I have a debian wheezy KVM mounting a share via CIFS, 
forcing UID and GID; UID/GID are the same on the two systems. I use a 
credentials file with non-root user and password. I disabled oplocks and 
client caching. The shared dir has ug+rw for all files, and has ug+x for all 
dirs; the same non-root user and group owns all files and dirs. I've even gone 
so far as to add ug+s on all dirs, to no avail. General access seems to be OK. 
But there's a failure in one specific instance.

On the KVM, I'm running unibasic (business basic). I wrote a program to test 
record locking when reading indexed ISAM files. Running it on two KVMs, I 
verified that record locking does work; the lock passed between the two 
programs very nicely. But I encountered a problem when creating indexed ISAM 

When a UB program builds an indexed ISAM DB, it creates both a data file and 
an index file on the file server. The problem is that it *always* fails when a 
non-root user runs unibasic (it can't create the index structure within the 
index file). But it succeeds when running the program as root. Oddly, if I 
leave ug+s off the dirs on the server, root:root will own one of the files in 
the pair (regardless of forceuid/forcegid on the client mount).

This is perplexing. The CIFS client mount generally works. But for this 
particular case, it always fails. The program does work correctly if I run it 
on the file server.

Where do I start looking to get to the root of the problem? In Debian's samba 
3.6.6? In Debian's CIFS module for linux 3.2? I can save a tcpdump of the 
packet exchanges in each case; but I've no idea how to decipher the packet 

Is it possibly related to how unibasic names the files? It uses a single name, 
say "myisam". The file containing the data records is named in lower case 
(myisam); the file containing the c-tree index(es) is named in upper case 
(MYISAM). I specified 'case sensitive = yes' in smb.conf and did not specify 
'nocase' in the CIFS mount. Is it possible CIFS or Samba (or both) are 
inadvertently performing a case insensitive compare? Or otherwise not 
differentiating between the two?


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