Suddenly inaccessible CIFS mounts on linux¶

We suddenly saw some failing CIFS (smb) mounts on servers in our (zabbix) monitoring.

• Hurray for monitoring and especially also custom monitoring scripts that caught this specific error.

• Huh? Why is it suddenly failing?

The error when (re)mounting the share:

mount error(112): Host is down

Pinging the host of course works just fine. 10 seconds of googling lead us to this serverfault.com answer which contained the solution: add vers=2.0 to your mount options.

The reason: if you’ve correctly (and recently) patched your windows servers, you’ve also disabled the SMB version 1 protocol. And somehow linux/smb doesn’t automatically detect version 2, so you have to set it explicitly.

There might be something that I’ve missed, but at least our CIFS mounts work again :-)