I have Ubuntu 11.10 as a host and another linux 2.6 distribution as a guest.

When I try to setup guest additions, this error message appears

Building the shared folder support module .. fail

And because of that, when I run the following in terminal

mount -t vboxsf shared /root/shared

I get the following error message

mount: unknown filesystem type 'vboxsf'

Any syggestions please?

EDIT

Sorry, the mentioned error message isn't complete, this is it.

Building the shared folder support module ...fail!
(Look at /var/log/vboxadd-install.log to find out what went wrong)

This is the content of vboxadd-install.log

    Uninstalling modules from DKMS
    Attempting to install using DKMS

    Creating symlink /var/lib/dkms/vboxguest/4.1.2/source ->
                     /usr/src/vboxguest-4.1.2

    DKMS: add Completed.

    Kernel preparation unnecessary for this kernel.  Skipping...

    Building module:
    cleaning build area....
    make KERNELRELEASE=3.2.6 -C /lib/modules/3.2.6/build M=/var/lib/dkms/vboxguest/4.1.2/build..........................(bad exit status: 2)

    Error! Bad return status for module build on kernel: 3.2.6 (i686)
    Consult the make.log in the build directory
    /var/lib/dkms/vboxguest/4.1.2/build/ for more information.
    0
    0
    ERROR: binary package for vboxguest: 4.1.2 not found
    Failed to install using DKMS, attempting to install without
    make KBUILD_VERBOSE=1 -C /lib/modules/3.2.6/build SUBDIRS=/tmp/vbox.0 SRCROOT=/tmp/vbox.0 modules
    test -e include/generated/autoconf.h -a -e include/config/auto.conf || (        \
        echo;                               \
        echo "  ERROR: Kernel configuration is invalid.";       \
        echo "         include/generated/autoconf.h or include/config/auto.conf are missing.";\
        echo "         Run 'make oldconfig && make prepare' on kernel src to fix it.";  \
        echo;                               \
        /bin/false)
    mkdir -p /tmp/vbox.0/.tmp_versions ; rm -f /tmp/vbox.0/.tmp_versions/*

      WARNING: Symbol version dump /usr/src/linux-source-3.2.6/Module.symvers
               is missing; modules will have no dependencies and modversions.

Actually the log file is very large and it exceeds the 30000 characters limit. How can I upload the entire log file here?