Getting "mount error(5): Input/output error" when mounting windows share on SLE 12 SP1

This document (7017413) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 12 SP1
SUSE Linux Enterprise Server 12

Situation

When trying to mount a Windows cifs samba share it would give the following error:

  mount error(5): Input/output error
  Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)

In SLE 11 SP3 the same command would work when mounting this same Windows share.
Here is a copy of the SP3 syntax that works:

mount -t cifs //server.suse.com:/home /mnt/test -o username=corpdom\\username

In SLE 12 SP1 a similar command would fail:

mount -t cifs //server.suse.com/home /mnt/test -o username=corpdom\\username

Here is the error on the command line after running this command:

mount error(5): Input/output error
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)

If you look at the end of "journalctl" you will see these errors:

Status code returned 0xc0000001 NT_STATUS_UNSUCCESSFUL
CIFS VFS: Send error in SessSetup = -5
CIFS VFS: cifs_mount failed w/return code = -5

Resolution

Add "sec=ntlm" to the options in the mount command.
Change "username=corpdom\\username" to "username=username,domain=corpdom"

Examples of a working SLE 12 SP1 mount command:

mount -t cifs //IPADDRESS/home /mnt/test -o username=username,domain=corpdom,sec=ntlm
mount --verbose -t cifs //IPADDRESS/home /mnt/test -o username=jmortenson,domain=corpdom,password=XXXXXXXX,sec=ntlm
mount --verbose -t cifs //server.suse.com/home /mnt/test -o username=username,domain=corpdom,password=XXXXXXXX,sec=ntlm

Example for /etc/fstab:

//IPADDRESS/home/ /mnt/test cifs rw,sec=ntlm,username=username,domain=corpdom,password=XXXXXXXX,sec=ntlm
//server.suse.com/home/ /mnt/test cifs rw,sec=ntlm,username=username,domain=corpdom,password=XXXXXXXX,sec=ntlm

Cause

A LAN trace revealed that mount.cifs in SLE 11 SP3 was using "ntlm" for the security mode.
A LAN trace revealed that mount.cifs in SLE 12 SP1 was using "ntlmssp" for the security mode.
Add the option "sec=ntlm" to the mount command to change the security mode to match SLE 11 SP3.

This syntax does not work with SLE 12 SP1 change "username=corpdom\\username" to "username=username,domain=corpdom"

Additional Information

smbclient worked fine so this proved that the user was allowed to see and use the Windows share.

smbclient -L IPADDRESS -U username -W corpdom
smbclient //server.suse.com/home -U username -W corpdom

Disclaimer

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