A few hours ago i made a full update via the software-center. The mounted shares allready worked fine, but after updating i just get this error message:

mount error(22): Invalid argument Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)

This is how my shares are mounted in fstab:

//IP-of-server/samba-directory  /Path-to-mount-point/ cifs users,noauto,uid=1000,gid=1000,credentials=/path-to-credentials,iocharset=utf8,sec=ntlm   0       0


mount -a

does not show any errors. Trying to access the share with the File-Explorer directly (using smb://path-to-server) works fine as well. I have allready tried to use the "vers" option, but with no success.


tail -f /var/log/kern.log


CIFS VFS: Unable to select appropriate authentication method!

Thank you for your help and replying

  • i have allready read link this post and all solutions doesn't seem to work, but adding vers=1.0 worked! So may edit this post and leave the quotes. But i actually do not know why this has changed. The server provides samba 2 and higher.
    – Greeny2408
    Commented Jan 11, 2018 at 19:29
  • vers= has to do with the [SMB]( en.wikipedia.org/wiki/Server_Message_Block) (Server Message Block) protocol and not SAMBA itself. SMB is the communications type where SAMBA is the server. Chances are when you upgraded CIFS, the SMB default type changed. It was probably trying to communicate at a different SMB version like 2.0, 2.1 or 3.0.
    – Terrance
    Commented Jan 11, 2018 at 19:48
  • Thank you Terrance for your fast reply! SMB was of course what i meant, sorry. The server itself should just use smb2 to smb3 (set min protocol = smb2 and max protocol = smb3) thats why i am confused that it works with vers=1.0 . cifs or cifs-utils package is at version 6.4 . But at least it works and thank you for your very nice explanation!:)
    – Greeny2408
    Commented Jan 11, 2018 at 20:54
  • I wonder if the authentication has to do with plain text passwords that it is using in the credentials file that is being transmitted. Try setting on the server in the [global] section both ntlm auth = no and client ntlmv2 auth = yes.
    – Terrance
    Commented Jan 11, 2018 at 21:30
  • 2
    removing sec=ntlm from fstab worked!
    – Greeny2408
    Commented Jan 12, 2018 at 15:00

3 Answers 3


I actually do not know why, but after update the sec=ntlm option for cifs in fstab does not work anymore and forced me to use the option vers=1.0. After removing sec=ntlm it works again. I think the new version of cifs uses a more secure dialect.

  • 2
    According to man mount.cifs the defaults (i.e. what you get if you don’t specify these options at all) are vers=1.0 and sec=ntlmssp. Commented Jan 14, 2018 at 7:06
  • 13
    I changed my sec=ntlm to sec=ntlmssp (hence the new default?) and it works for me now. I still have vers=3.0 as well. Commented Feb 6, 2018 at 8:45
  • @IanGallagher I will give it a try and will post the results. Thank you!
    – Greeny2408
    Commented Feb 21, 2018 at 19:06
  • confirmed. After removing sec=ntlm it worked again Commented Jan 1, 2019 at 10:11
  • 2
    sec=ntlmssp setting this option in fstab worked for me. Commented Mar 11, 2019 at 7:40

I just had the same issue with this line in fstab and after upgrading Ubuntu

//$ /mnt/toruk/d  cifs credentials=/etc/winpassword.txt,iocharset=utf8,sec=ntlm,ro 0 0

Which got me the same error message on the command line:

# mount /mnt/toruk/d
mount error(22): Invalid argument
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)

and in /var/log/syslog

Sep 14 22:48:13 truhe kernel: [67664.396524] CIFS VFS: Unable to select appropriate authentication method!
Sep 14 22:48:13 truhe kernel: [67664.396529] CIFS VFS: Send error in SessSetup = -22
Sep 14 22:48:13 truhe kernel: [67664.396658] CIFS VFS: cifs_mount failed w/return code = -22

Adding the parameter vers=1.0 did make it work again, however the default was changed for a reason, and there had to be something better than fall back to the insecure deprecated protocol.

Thanks to this answer and comments I could get it to work again by not using vers, but changing sec=ntlmssp

//$ /mnt/toruk/d  cifs credentials=/etc/winpassword.txt,iocharset=utf8,sec=ntlmssp,ro 0 0
  • Thank you! Connecting Ubuntu 19.04 with with Windows server 2019. the config previously had sec=ntlm, changing it to ntlmssp worked, but removing the sec param entirely worked great too!
    – DanO
    Commented Sep 13, 2019 at 7:01
  • that ,sec=ntlmssp works great for mine on Pop!_OS/Ubuntu 22.04
    – Kokizzu
    Commented Jan 7 at 21:39

I am using pam_mount to automatically mount drives on login. When I updated to Xubuntu 16.04.3 the login process would no longer complete. It just hung. I tested manually mounting CIFS shares and saw that it never exited from the mount command.

I had to add a vers=1.0 to the mount options to mount cifs shares from my SuSE CIFS shares. Once I did that everything worked fine.

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