[Libguestfs] [PATCH] Fix mkinitrd detection of LVM root on RHEL 4

[Richard W.M. Jones]

On Tue, Aug 03, 2010 at 05:32:24PM +0100, Matthew Booth wrote:
> RHEL 4's mkinitrd will fail to recognise that root is on LVM when running on a
> recent kernel/udev due to changes in naming. This patch detects LVM root for
> RHEL 4, and uses a dirty hack to frig mkinitrd if required.
> 
> Fixes RHBZ#580461
> ---
>  lib/Sys/VirtV2V/GuestOS/RedHat.pm |   21 +++++++++++++++++++--
>  1 files changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/Sys/VirtV2V/GuestOS/RedHat.pm b/lib/Sys/VirtV2V/GuestOS/RedHat.pm
> index 101a64b..74b9de1 100644
> --- a/lib/Sys/VirtV2V/GuestOS/RedHat.pm
> +++ b/lib/Sys/VirtV2V/GuestOS/RedHat.pm
> @@ -1639,13 +1639,14 @@ sub prepare_bootable
>      my @modules = @_;
>  
>      my $g = $self->{g};
> +    my $desc = $self->{desc};
>  
>      # Find the grub entry for the given kernel
>      my $initrd;
>      my $found = 0;
>      eval {
>          my $prefix;
> -        if ($self->{desc}->{boot}->{grub_fs} eq "/boot") {
> +        if ($desc->{boot}->{grub_fs} eq "/boot") {
>              $prefix = '';
>          } else {
>              $prefix = '/boot';
> @@ -1720,7 +1721,23 @@ sub prepare_bootable
>                  $g->modprobe('loop');
>              };
>  
> -            $g->command(['/sbin/mkinitrd', @module_args, $initrd, $version]);
> +            my @env;
> +
> +            # RHEL 4 mkinitrd determines if the root filesystem is on LVM by
> +            # checking if the device name (after following symlinks) starts with
> +            # /dev/mapper. However, on recent kernels/udevs, /dev/mapper/foo is
> +            # just a symlink to /dev/dm-X. This means that RHEL 4 mkinitrd
> +            # running in the appliance fails to detect root on LVM. We check
> +            # ourselves if root is on LVM, and frig RHEL 4's mkinitrd if it is
> +            # by setting root_lvm=1 in its environment. This overrides an
> +            # internal variable in mkinitrd, and is therefore extremely nasty
> +            # and applicable only to a particular version of mkinitrd.
> +            if ($desc->{distro} eq 'rhel' && $desc->{major_version} eq '4') {
> +                push(@env, 'root_lvm=1') if ($g->is_lv($desc->{root_device}));
> +            }
> +
> +            $g->sh(join(' ', @env).' /sbin/mkinitrd '.join(' ', @module_args).
> +                   " $initrd $version");
>          }
>  
>          else {

Looks OK, ACK.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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