mount - Mounting cifs share using kerberos fails with 'Operation not supported'

Question

I'm trying to mount a network share using cifs and kerberos on a CentOS 8 distro. I am able to mount the share correctly using my explicit credentials, but passing the option of sec=krb5 doesn't work. The response from the operation says: 'mount error(95): Operation not supported.' I'm also not able to see any info about the failed operation when calling dmesg.

Other SO answers have said to add 'vers' to the options string, but that doesn't seem to work either. If I add vers=1.0, I get the error 'Function not implemented', which I assume is because SMB 1.0 is disabled. Any other value for vers give the 'operation not supported error.'

Here is the command I'm using: mount -t cifs //server/folder /mnt/prog -o sec=krb5,vers=3.02

Not sure if it's relevant, but when I enable verbose messaging in the mount, it shows it has added user=root,pass=**** to the options.

I know the kerberos ticket is fine as I'm able to connect and list the shares using smbclient -k -L //server. When I change the debug level on smbclient to something higher, I can see the dialect negotiated with the server to be [SMB3_02], so I assume my SMB dialect is 3.02, which is what I used in the vers option for the mount.

FWIW, I get the same error within a privileged docker container and WSL2 on Windows using Ubuntu. I also get the same error when trying it through fstab.

My first question is how to get more explicit errors (or any) to show in dmesg so I can troubleshoot more effectively.

The other question is more generally how to fix the mount issue I mentioned above. Any help is appreciated. Thanks!

Answer 1

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