Hi Frank, 

Thanks a lot for your quick answer. I have tried your suggested change:

[root@vdicube_pub_ceph_nfs /]# cat /etc/ganesha/ganesha.conf

NFSV4
{
   Allow_Numeric_Owners = false;
}

NFS_KRB5
{
   PrincipalName = nfs;
   KeytabPath = /etc/krb5.keytab;
   Active_krb5 = false;
}

NFS_CORE_PARAM
{
        # Enable NLM (network lock manager protocol)
        Enable_NLM = false;
}

EXPORT
{
        # Export Id (mandatory, each EXPORT must have a unique Export_Id)
        Export_Id = 2046;

        # Exported path (mandatory)
        Path = /;

        # Pseudo Path (for NFS v4)
        Pseudo = /;

        # Access control options
        Access_Type = NONE;
        Squash = No_Root_Squash;
        Anonymous_Uid = -2;
        Anonymous_Gid = -2;

        # NFS protocol options
        Transports = "TCP";
        Protocols = "4";

        SecType = "sys";
        Manage_Gids = true;

        CLIENT {
            Clients = 192.168.100.104,192.168.100.105;
            Access_Type = RO;
        }

        # Exporting FSAL
        FSAL {
            Name = CEPH;
            User_Id = "admin";
        }
}

LOG {
        Default_Log_Level = WARN;
        Components {
                # ALL = DEBUG;
                # SESSIONS = INFO;
        }
}

[root@vdicube_pub_ceph_nfs /]#

 28/01/2019 23:15:18 : epoch 5c4f7ef5 : vdicube_pub_ceph_nfs : ganesha.nfsd-
> 25[main] nfs_Init_svc :DISP :CRIT :Cannot acquire credentials for principal nfs,

This one can be made to not happen by setting:

NFS_KRB5
{
        Active_krb5 = false;
}

You are right, the previous message has dissappeared!

> 28/01/2019 23:15:18 : epoch 5c4f7ef5 : vdicube_pub_ceph_nfs : ganesha.nfsd-
> 25[main] nfs_Init_admin_thread :NFS CB :EVENT :Admin thread initialized,
> 28/01/2019 23:15:18 : epoch 5c4f7ef5 : vdicube_pub_ceph_nfs : ganesha.nfsd-
> 25[main] nfs_rpc_cb_init_ccache :NFS STARTUP :EVENT :Callback creds
> directory (/var/run/ganesha) already exists,

This one perhaps should not be an EVENT, maybe just an INFO, or maybe silent (with perhaps a INFO if it IS created). 

I have deleted the folder /var/run/ganesha before run ganesha and messages have disappeared too. 

> 28/01/2019 23:15:20 : epoch 5c4f7ef5 : vdicube_pub_ceph_nfs : ganesha.nfsd-
> 25[main] nfs_rpc_cb_init_ccache :NFS STARTUP :WARN
> :gssd_refresh_krb5_machine_credential failed (-1765328160:0),

Hmm, the code that generates this perhaps should not be executed if Active_krb5 = false. 

Unfortunately not. Messages are still in the log: 

05/02/2019 22:14:08 : epoch 5c59fc9f : vdicube_pub_ceph_nfs : ganesha.nfsd-25[main] nfs_rpc_cb_init_ccache :NFS STARTUP :WARN :gssd_refresh_krb5_machine_credential failed (-1765328160:0)

The statd daemon is not necessary for NFS v4 only, and Enable_NLM = false is just fine in that case. NLM is Network Lock Manager, the lock protocol for NFS v3. 

Let me another question regarding parallel services. sssd and rpcbind ara necessary for nfsv4 too? 

You can also set Protocols = 4 in NFS_CORE_PARAM to completely disable NFS v4 (and 9P). 

I don't want to disable nfsv4... :S. Please can you clarify?

Thanks a lot.