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The Problem

I have a directory that is shared by a Windows Server 2012 R2. Some Linux clients (Ubuntu 14.04) mount this share via /etc/fstab:

//10.1.1.1/MyShare /mnt/myshare cifs rw,nounix,noserverino,sec=ntlm,_netdev,iocharset=utf8,user=myuser,password=mypassword,uid=1000,gid=1000 0 0

Although working perfectly for some time, every now and then (e.g., after 1-2 hours) the mount becomes inaccessible and all processes using (or trying to access) it hang for about 5 minutes. After that, normal operation continues again for a few hours when it hangs again. Windows clients can access the share without any problem.

Before migrating to Windows Server 2012 R2, the directory was shared by a Windows 7 VM running on a Windows Server 2008. This worked perfectly fine (for the same Linux client configuration).

I can see four possible causes for the malfunction:

  • Bug in Windows Server 2012 R2
  • Bug in cifs-utils
  • Network/hardware problems (unlikely because no problems with Windows clients)
  • Wrong configuration of sharing/mounting

The Question

The purpose of this question is basically to eliminate the possibility of wrong server or client configuration by asking how the correct/optimal setup should look like. Of course, any other hint is welcome, too.

1. Linux Side

What mount.cifs options should I use to mount a Windows Server 2012 R2 Share in Linux (via fstab)? E.g., what about the optimal values for vers, sec, iocharset, etc? Should I use nounixor noserverino or any other parameters?

Additional information:

  • Authentication is done using a local user on the Windows Server, so the Acitve Directory/domain should not be involved.

  • CIFS Version 2.02

  • $ mount.cifs -V

    mount.cifs version: 6.0

  • $ cat /proc/version

    Linux version 3.13.0-45-generic (buildd@phianna) (gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1) ) #74-Ubuntu SMP Tue Jan 13 19:36:28 UTC 2015

2. Windows Side

Are there any special settings on the Windows Server side to improve the Windows/Linux interoperability?

@mods: Please do not migrate this to Unix & Linux because I had already posted it there 3 months ago (and deleted it now as no one has posted an answer).

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    Download Microsoft Message Analyzer. It's packet capture software that has specific decoders for analyzing SMB traffic. If you can capture one of those disconnects, that might give you a clue.
    – longneck
    Feb 19, 2015 at 16:55
  • You have given no details about network configuration, especially: are machines in the same subnet or routed, firewall hardware & software in between... This pretty much looks like a firewall issue - have you tried disabling it completely on Windows server? Sometimes it makes sense to just switch firewall policy from dropping packets to rejecting them (to avoid waiting for timeouts), in Windows Firewall it's possible using registry key.
    – sam_pan_mariusz
    Feb 19, 2015 at 19:37
  • @longneck - +1 for Microsoft Message Analyzer hint. I've never heard of this tool, and here it seems more suitable than ie. Wireshark.
    – sam_pan_mariusz
    Feb 19, 2015 at 19:40
  • I do not have an answer to this question, but am experiencing the same problem. We have Ubuntu 12.04 machines that hang on Windows Server 2012 shares. The Ubuntu machines also have Windows Server 2008 shares mounted without any issues. The machines were upgraded to Ubuntu 12.04 from 10.04. When they were running Ubuntu 10.04 this issue did not exist, only after upgrading and only on the Windows 2012 shares. The Windows Shares (2008 and 2012) are all on the same subnet and the Ubuntu machines are on the a different subnet from the Windows Servers.
    – FatMetalMan
    Sep 16, 2015 at 18:15

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