[nSLUG] Virtualbox problem (was Re: Debian vserver kernel)

Jack Warkentin jwark at eastlink.ca
Sat Nov 8 21:19:07 AST 2008

Hi Everybody

Well I found a solution.

To understand the solution it must be realized that the standard 
GNU/Linux "mount" command does not directly perform mounts of virtualbox 
shared folders. Instead it invokes the program "/sbin/mount.vboxsf" 
which is supplied by virtualbox to perform these mounts.

The problem seems to be an improper communication between "mount" and 
"/sbin/mount.vboxsf". When the "mount" is issued from the command line 
everything works fine, but when it is issued from a shell script, or as 
a result of an entry in /etc/fstab it doesn't.

What worked was to remove the entry from /etc/fstab completely, to never 
issue "mount" on the shared folder except from the command line, and to 
replace the "mount -a" in /etc/rc.local with

mount.vboxsf -o ro,uid=1004,gid=1004 FullHost /FullHost

Hope this helps other potential users of virtualbox.



Jack Warkentin wrote:
> Hi everybody
> I switched almost completely to GNU/Linux from Windows 98 five or so 
> years ago. My only remaining need for Windows is for doing my income 
> tax. (I refuse to use a web-based application where the data is stored 
> on somebody else's machine.)
> I have been using a virtualization product called Win4Lin home with 
> Windows 98, which uses a patched kernel and is no longer supported. I 
> have an unactivated copy of Win XP SP2 which I would like to set up in a 
> virtual machine. After reading about KVM, Xen, Qemu and Virtualbox I 
> decided to try out Virtualbox.
> But first, as an experiment, and to gain some experience, I decided to 
> set up a 32-bit Debian testing system in a Virtualbox vm on my 
> AMD64-based laptop, where I ran into some difficulties.
> Setting up the vm from the GUI interface and installing 32-bit Debian 
> testing went smoothly. I also succeeded (eventually, had to find an 
> appropriate kernel and compile environment) in installing the Guest 
> Additions and managed to enable sharing of my full file system by including
> <SharedFolder name="FullHost" hostPath="/" writable="false"/>
> in the vm's definition file, and
> FullHost  /FullHost  vboxsf  noauto,users,ro,uid=1004,gid=1004  0   0
> in its /etc/fstab file.
> The root of my problem is that /sbin/mount.vboxsf (the 
> Virtualbox-provided binary that gets invoked by the mount command) will 
> not allow ordinary users to mount FullHost, no matter what options (most 
> of which are not allowed) I try putting into the fstab file.
> Removing the "users," from fstab allows root to perform the mount 
> successfully from the command line.
> But I didn't want to have to su to root in order to perform this mount 
> every time. So I removed the "noauto," from fstab and tried again. Here 
> is the result from the /var/log/boot file (with the date/timestamps and 
> several irrelevant lines removed):
> Mounting local filesystems.../sbin/mount.vboxsf: mounting failed with 
> the error: No such device
> ^[[31mfailed.^[[39;49m
> Activating swapfile swap...done.
> INIT: Entering runlevel: 2
> Starting VirtualBox Additions ...done.
> Starting VirtualBox host to guest time synchronisation  ...done.
> Starting VirtualBox Additions shared folder support/sbin/mount.vboxsf: 
> mounting failed with the error: Protocol error
> The first failure is understandable - the virtualbox daemons had not yet 
> been started. But the second is not understandable. In the first place, 
> why would there be a second attempt at the mount? In the second place, 
> why would it fail, when root is able to perform the mount successfully 
> from the command Line?
> So I finally tried putting the mount command into /etc/rc.local as follows.
> . /lib/lsb/init-functions
> log_action_msg "In rc.local, about to execute \"mount -a\""
> mount -a
> log_action_msg "$? returned from \"mount -a\" in rc.local"
> (The first line is to make the log_action_msg function available.)
> The results were disappointing. Again from /var/log/boot
> In rc.local, about to execute "mount -a".
> /sbin/mount.vboxsf: mounting failed with the error: Protocol error
> Note that not only did the mount fail, but that the mount command never 
> returned to the rc.local script for execution of the last log message 
> command.
> I suppose I should address the first problem (mount failure) to the 
> virtualbox team and the second (return failure) to the Debian people, 
> but since Eugene seems to have had a lot of experience with virtualbox I 
> thought maybe he might be able to shed some light on this.
> Any help, from anybody, would be much appreciated.
> Jack
> Eugene Cormier wrote:
>> On Fri, 2008-11-07 at 09:11 -0400, D G Teed wrote:
>>> I see a lot of the chatter around vserver is from 2005ish, and not
>>> much
>>> recent.  Is there something more commonly used now?  Xen?
>>> Virtualbox?  OpenVZ?  VMware?  Or should I look at compiling
>>> my own kernel for vserver?
>> Donald, depending on what you're doing (and I assume you're probably
>> doing some kind of linux server as opposed to running windows) then I
>> would say the way to go is to use Xen or KVM ......personally though I
>> like to toy with different OS' so I started using Virtualbox (which I
>> love) and I've recently setup a http server on it....it's been rock
>> solid (no crashes or other problems) for about 2 years now
>> Eugene 

Jack Warkentin, phone 902-404-0457, email jwark at eastlink.ca
39 Inverness Avenue, Halifax, Nova Scotia, Canada, B3P 1X6

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