Issue NFS between host and VM

Ernie95 · Saturday at 12:22

Hi All,

I am trying to mount a nfs folder from a nfs server which is in a proxmox VM.

in the VM i see the exports :

Code:

nas4free: ~# showmount -e
Exports list on localhost:
/mnt/pool1/proxmox/save/toto       192.168.150.0

pool1/proxmox is a dataset
pool1/proxmox/save is a dataset
toto is a folder (I try also as only dataset was with error also)

On my node pve the command line:

Code:

pvesm scan nfs 192.168.150.21

displays

Code:

clnt_create: RPC: Program not registered
command '/sbin/showmount --no-headers --exports 192.168.150.21' failed: exit code 1

Iptables of the node show :

Code:

root@pve:~# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination     
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:nfs
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:sunrpc
ACCEPT     udp  --  anywhere             anywhere             udp dpt:nfs
ACCEPT     udp  --  anywhere             anywhere             udp dpt:sunrpc

I try to in datacenter in storage :

and I have this error

Same error if I export in the vm a folder or a dataset.

I tried to modify directly the file /etc/pve storage.conf
The storage appears but the item Save-NFS in the node as a ? and if I select the item, same error (500).

No firewall is active at this moment (datacenter level and vm level)

How can I solve this 500 error ?
Or what I need to look in order that host and the VM can have a common share ? NFS or other options ?

Thanks

waltar · Saturday at 13:35

Export pool1/proxmox and pool1/proxmox/save too.

Ernie95 · Saturday at 14:29

Thanks
Done but same issue :

Code:

nas4free1: ~# showmount -e 192.168.150.21
Exports list on 192.168.150.21:
/mnt/pool1/proxmox/save       192.168.150.0
/mnt/pool1/proxmox                 192.168.150.0

I cannot have /mnt/pool1/proxmox/save + /mnt/pool1/proxmox/save/toto as i have the option for the subfolders display.
Error :

Code:

create storage failed: mount error: mount.nfs: access denied by server while mounting 192.168.150.21:/mnt/pool1/proxmox/save/toto (500)

If I modified the storage.cfg:

Code:

nfs: NFS-pve
        export /mnt/pool1/proxmox/save
        path /mnt/pve/Save
        server 192.168.150.21
        content backup
        options soft,vers=4.2

Same error 500 (also with default, 4 or 4.1 in option)

I can access to the nfs from other computer without issue

Ernie95 · Saturday at 14:30

I am thinking if it is an issue of mapall or maproot. I use mapall - root.

waltar · Saturday at 15:55

export with options rw,no_root_squash

Ernie95 · Saturday at 16:37

My server nfs in the VM is with Freebsd. I added maproot=root (equivalent to no_root_squash).

Same issue.

Ernie95 · Saturday at 16:38

And manual mount : same issue

Code:

root@pve:~# mount -t nfs 192.168.150.21:/mnt/pool1/proxmox/save /mnt/pve/Save
mount.nfs: access denied by server while mounting 192.168.150.21:/mnt/pool1/proxmox/save

waltar · Saturday at 18:48

So what is freebsd as a fileserver worth for if it's denied access to it's client which tried to access as root ?
So as you wrote your nas is a vm and get it's disks from pci passthrough ctrl. what is that worth if you even cannot move it to other pve host ?
Give the disks to pve and give it a nfs-server and your main problem is gone while for the secondary you would need external storage enclosure.

Ernie95 · Saturday at 19:03

Thanks, so the passthrough of the full disk to the VM blocks the access by the host. Am I right ?
I thought that the nfs share or samba share of the vm will allow the share.

Same issue with SMB share : no access.

waltar · Saturday at 19:31

No passthrough don't block the access as it's done by other protocol like nfs or smb.
"...access denied by server..." is definitive an export definition problem.

Ernie95 · Saturday at 20:39

I will investigate as same issue with smb.

Thanks again for your help

waltar · 2025-09-07T07:39:01+0200

Maybe netmask missing in your export definitions (as you just show showmount -e IP outcome) ?
Like eg /mnt/pool1/proxmox 192.168.150.00/24(options)

silverstone · 2025-09-07T09:51:01+0200

Ernie95 said:
I will investigate as same issue with smb.

Thanks again for your help

I am doing the reverse (NFS Export on the Proxmox VE Host to a Debian VM, Private Network in this Case otherwise NFS via Wireguard if remote Host) but I'd say that your /etc/exports seems way too simple ...

Here is mine for Comparison that ONLY grants access to the Host 172.30.1.2/32:

Code:

# Docker Mirror (Private Network)
/zdata/nfs/docker-mirror    172.30.1.2/32(rw,no_root_squash,nohide,sync,no_subtree_check,fsid=100)

With /etc/fstab on the Guest:

Code:

# Docker Mirror Data Storage
172.30.1.1:/zdata/nfs/docker-mirror        /mnt/docker-mirror            nfs    rw,user=podman,auto,nofail,x-systemd.automount,mountvers=4.0,proto=tcp        0       0

Important to remember to restart NFS Server & re-export all Shares whenever you add new or change existing Shares including their Options:

Code:

exportfs -a
exportfs -rv
systemctl restart nfs-kernel-server

Is 192.168.150.0 really the IP of your Proxmox Host ?

I usually always add the Netmask suffix to the /etc/exports Line, typically /32 (Single Host) or /24 for a 255.255.255.0 Netmask.
Not sure if that is a Problem or not in your Case, but worth checking out

.

Ernie95 · 2025-09-07T15:25:15+0200

Thanks Silverstone.
My VM with passthrough (HBA and other specific disks) contains Xigmanas (based on freebsd).
I set up in Xigmanas a nfs server :
- nfs v4
- several exports : dataset and a folder as I have issue of access (in order to try also).

This results of command comes from the freebsd VM with Xigmanas:

Code:

nas4free1: ~# showmount -e 192.168.150.21
Exports list on 192.168.150.21:
/mnt/pool1/proxmox/save       192.168.150.0
/mnt/pool1/proxmox                 192.168.150.0

It is 192.168.150.0 for access to all local machine on this local network. It is a home server not enterprise purpose.

In my freebsd VM the export file is

Code:

/mnt/pool1/proxmox -alldirs -network 192.168.150.0/24
/mnt/pool1/proxmox/save -alldirs -network 192.168.150.0/24

I tested also options:
- -mapall="root"
- -maproot="root"
instead of -alldirs

In freebsd, mapall seems to be in Debian no_root_squash.
All the tests was not successfull (access denied, error 500).

I understand your reverse idea. I began to set up a dataset on my local disk : I enable sharenfs

Code:

ZFS_Mirror_PVE/share                     sharenfs  on        local

Then I tested this command : on proxmox IP adress (20) and on VM adress (21)

Code:

root@pve:~# pvesm scan nfs 192.168.150.20
/ZFS_Mirror_PVE/share *
root@pve:~# pvesm scan nfs 192.168.150.21
/ZFS_Mirror_PVE/share *

I am surprised to have the same results. Only host should show the nfs share not the vm.

I think I misunderstand a logic of proxmox.

Thanks for any advice

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