Cant open file for writing with cifs mount

Question

Hi I have mounted my QNAP on to a drive on my ubuntu machine using the following fstab entry

//<ip-address>/Documents/Aly /home/aly/Documents cifs credentials=/root/.credentials,uid=1000,gid=1000,rw,hard,dir_mode=0777,file_mode=0777 0 0

this gives the following permisssions:

drwxrwxrwx  1 aly aly    0 2011-12-03 12:18 .
drwxr-xr-x 13 aly aly 4096 2011-12-03 12:14 ..
-rwxrwxrwx  1 aly aly    5 2011-12-03 11:55 test.tst
drwxrwxrwx  1 aly aly    0 2011-11-26 17:54 VirtualBox VMs

I have permissions to delete files and add files, however when trying to write to a file i.e. test.tst I get the following error in vi:

"test.tst" E212: Can't open file for writing

Has anyone seen this before, if i mount the drive via nfs this is not an issue, however nfs lacks the security i desire.

EDIT

The solution I have come to is:

<ip-address>:Documents/Aly/ /home/aly/Documents cifs hard,noperm,nouid,credentials=/root/.credentials,iocharset=utf8,file_mode=0777,dir_mode=0777,nodfs 0 0

Answer 1

You could try the nodfs parameter (if supported) as explained in the article
How to workaround the DFS samba bug on the DNS323 NAS ? :

Firstly, here is a quick bug description: It's impossible to modify any existing files. The "Not a directory" or "No such file or directory" or "touch: setting times of…" errors occurs when trying to modify a file.

If your linux cifs or smbfs client support the nodfs flag (integrated in kernels > 2.6.27). You just have to add this option to the mount command. Example:

mount -t cifs -o credentials=/home/kerphi/.smb-zekra-credentials,iocharset=utf8,file_mode=0777,dir_mode=0777,nodfs //zekra/Volume_1 /home/kerphi/zekra

If you cannot upgrade your kernel (like me because i'm following the debian releases), you have to follow this workaround:

• Connect to the DNS323 using the web GUI and goto tools→system.
• Save the configuration to your workstation (in "CONFIGURATION SETTINGS" section).
• After saving edit the file and just under this line:
  ;[ global ]
  add the following line:
  msdfs root = no
  Then upload this file through the web interface, your NAS will reboot and you will be able to modify existing file again !

This is further explained in CIFS: Add nodfs mount option :

Older samba server (eg. 3.0.24 from Debian etch) don't work correctly, if DFS paths are used. Such server claim that they support DFS, but fail to process some requests with DFS paths. Starting with Linux 2.6.26, the cifs clients starts sending DFS paths in such situations, rendering it unuseable with older samba servers.

The nodfs mount options forces a share to be used with non DFS paths, even if the server claims, that it supports it.

Answer 2

when trying to write to a file

Write with root privilidges, then it will most probably work (rw options given)