VirtualBox: Slackware64 host and guest; NFS mount from host fails

catkin · 11-15-2010, 06:54 AM

Hello

This is similar to my LQ thread VirtualBox: how to NFS mount in Knoppix guest from Slackware host? but now the guest is Slackware64 13.1 like the host and it's not a one-off requirement that I can work around.

The host is an NFS server exporting /home/c/d to the 192.168.168.0/24 LAN:

Code:

root@CW8:~# exportfs
/home/c/d         192.168.168.0/24

This NFS export is routinely mounted by my netbook using mount -t nfs -o bg,rw,soft 192.168.168.0:/home/c/d /mnt/CW8d

So it should (TM) be straightforward to mount it from the guest which is currently configuring its eth0 using DHCP from the LAN router's DHCP service (the same as the netbook), can ping the host, do name resolution and has no firewall:

Code:

root@vCW8:~# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 08:00:27:30:1f:8a  
          inet addr:192.168.168.201  Bcast:192.168.168.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe30:1f8a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3147 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2548 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:3036808 (2.8 MiB)  TX bytes:248836 (243.0 KiB)
          Interrupt:19 Base address:0xd020
root@vCW8:~# ping -c1 192.168.168.7
PING 192.168.168.7 (192.168.168.7) 56(84) bytes of data.
64 bytes from 192.168.168.7: icmp_req=1 ttl=64 time=0.311 ms
[snip]
root@vCW8:~# dig linuxquestions.org
[snip]
;; ANSWER SECTION:
linuxquestions.org.    1440    IN    A    75.126.162.205
[snip]
root@vCW8:~# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destinatio

The host also has no firewall (same iptables -L output)

Running Wireshark on both host and guest shows NFS packets going from guest and being received on the host but nothing going the other way.

Running rpc.nfsd with -d and -s options and re-trying the mount from the guest produces nothing in the /var/log/* files and /var/log/nfsd/ is empty. Mounting from the netbook results in a line in /var/log/messages: mountd[24273]: authenticated mount request from 192.168.168.200:967 for /home/c/d (/home/c/d).

On the basis of this evidence it seems the packets from the guest, intended to initiate the NFS mount, reach the host's NIC but do not reach the host's NFS daemons. I do not know where VirtualBox networking fits within the architecture -- whether Wireshark's showing the packets arriving at the host means they have already traversed VirtualBox networking or not.

How to analyse this problem further?

VirtualBox on the host is PUEL 3.2.8 r64453. There is an unresolved issue on the guest in which boot initialisation of VirtualBox Guest Additions results in
Starting the VirtualBox Guest Additions ...fail!
(modprobe vboxsf failed)
which is a low priority issue because I wasn't planning on using VirtualBox Shared Folders (but might need to as a workaround for the NFS problem!).

Best

Charles