How to limit NFS access to the SVM root volume
Applies to
ONTAP 9
Description
- By default, when an SVM is created, the root volume is configured with 755permissions.
- This means that:
    - The user root (0) has effective permissions of 7, orFull Control.
- The Group and Others permission levels are set to 5, which isRead & Execute.
 
- The user root (0) has effective permissions of 
- When this is configured, everyone who accesses the SVM root volume can list and read junctions mounted below the SVM root volume.
- In addition, the default export policy rule that is created when an SVM is configured using System Manager or vserver setupcommands permits user access to the SVM root.
cluster::> vserver export-policy rule show -vserver nfs_svm -policyname default -instance
 
                                    Vserver: nfs_svm 
                                Policy Name: default 
                                 Rule Index: 1 
                            Access Protocol: any 
Client Match Hostname, IP Address, Netgroup, or Domain: 0.0.0.0/0 
                             RO Access Rule: any 
                             RW Access Rule: any 
User ID To Which Anonymous Users Are Mapped: 65534 
                   Superuser Security Types: none 
               Honor SetUID Bits in SETATTR: true 
                  Allow Creation of Devices: true 
- For example, if an SVM has 3 data volumes named "nfs4", "ntfs", and "unix"
- All would be mounted under "/" and can be listed with the lscommand by any user accessing the mount.
Example:
# mount | grep /mnt 
x.x.x.e:/ on /mnt type nfs (rw,nfsvers=3,addr=x.x.x.e) 
# cd /mnt 
# ls 
nfs4  ntfs  unix 
