Kernel panic: VFS: Unable to mount root fs on

  • Ferran Jorba

    Ferran Jorba - 2001-02-06

    Hi Sbastien,

    let me start to use this list.

    First of all, 2.0 looks very promising to me.  I've configured replicator.conf,
    NFS, etc. and double-checked that NFS server works, but the floppy disk

    First, the target machine I'm working with already has Debian installed, so
    hardware (including network cards) are detected fine, DHCP configures
    the network, etc..

    The grub menu shows three options.  I understand that I should use
    'Boot with DHCP and install a DHCP target'.

    The machine boots, recognises the network card, but lastly it stops

    Kernel panic: VFS: Unable to mount root fs on 00:00

    Any ideas?


    Ferran Jorba
    Universitat Autnoma de Barcelona

    • Sébastien Chaumat


      Seems like the miniroot-server is not know to the bootdisk.
      Or the miniroot is not correctly exported.

      First check: look at the kernel commandline:
        -either in he output of repli-bootdisk (at the very begining)
        -either at the begining of the kernel message on your target
          just after booting.

      You should see something like:

      nfsroot=$miniroot_server:$nfsroot,$miniroot_nfsopts ip=dhcp

      with $miniroot_server the IP address of the model
      $nfsroot: the correct path to the miniroot filesystem

      if all this is correct look at the log messages of the nfs-server
      to see if the mount request was received or not, if it was blocked or not.


      • Ferran Jorba

        Ferran Jorba - 2001-02-07

        Hi Sbastien,

        miniroot-server is apparently well defined.  According to the grub command line:

        kernel=/vmlinuz root=/dev/nfs nfsroot=158.109.x.y:/export/install/miniroot,
        rsize=8192,wsize=8192 up=dhcp

        where I have obscured the real IP number by x.y.  I suspect about two things:
        - /dev/nfs:  This device doesn't seem to be created by replicator.
        - kernel with root NFS support.  Should I need a special kernel?  My rescue
          discs are kenel-2.2.17-idepci.  Do I need a special kernel?  This one successfully
          recognises my network card.

        Or I am completely confused.

        The last lines of the client boot messages are:

        pcnet32.c: PCI buis is present, checking for devices...
        PCI Master Bit has not been set.  Setting...
        Found PCnet/PCI at ...
        eth0: PCnet/PCI II etc etc.
        Partition check:
          hda: hda1 hda2
        apm: BIOS version 1.2 Flags etc
        apm: diabled on user request.
        VFS: cannot open root device 00:00
        Kernel panic: VFS: Unable to mount root fs on 00:00

        And there is *no* activity on the NFS server



    • Sébastien Chaumat

      You definitevely need to recompile a kernel with NFS support as explained in the documentation:

      Compiling  a boot kernel for target

      Compile a kernel with all the necessary driver for the computer target. Do not use modules for the drivers required at boot time (typically network and SCSI).

      Add the following option during configuration of the kernel:

      *Networking options / IP: kernel level autoconfiguration
      *Networking options / IP: kernel level autoconfiguration / DHCP support
      *Filesystems / Network File Systems / NFS filesystem support
      *Filesystems / Network File Systems / NFS filesystem support / Root file system on NFS

      Maybe I should create a replicator-kernel.deb


      • Ferran Jorba

        Ferran Jorba - 2001-02-12

        Hi Sbastien,

        > You definitevely need to recompile a kernel with NFS support as explained in the
        > documentation:

        it worked!  Sorry for not being able to spot this.  As a matter or fact, I didn't do
        it because the standard Debian kernel was good enough for me, my idea was
        not to do "exotic" things.  May I suggest a small improvement in the documentation?
        Something like:  "You *must* create such a kernel because the standard Debian
        kernels do not have nfs support enabled.  However, this kernel will only be used
        for the installation diskette, and later on you can use your preferred standard Debian

        During my trial-and-error procedure, I also missed to enable write access to the
        nfs rootserver.  My opinion is this is something that would be nice to improve,
        for example, enabling RAM filesystem support into the boot kernel and mountin
        /proc, /etc and maybe something else there.  This way, perhaps nfs server could
        be configured to be read-only.  Now, it is a nasty security hole.

        I'm having minor problems now, like the repli-postinst script not working due to
        nfs server not responding after the storm of rsync.  Strange....

        Thanks a lot for your wonderful tool,



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