Cifs Mount in Fstab Does Not Work After Update

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.

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

//10.0.0.10/D$ /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

//10.0.0.10/D$ /mnt/toruk/d  cifs credentials=/etc/winpassword.txt,iocharset=utf8,sec=ntlmssp,ro 0 0

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.