Re: [Vserver] 64bit environment

From: Admin <>
Date: Thu 07 Sep 2006 - 14:49:50 BST
Message-Id: <>

On Thursday 07 September 2006 21:52, Chuck wrote:
> I am getting ready do set up a new vserver host using Opterons.. however
> some of the guests will be pre-compiled 32bit such as CentOS.. if the host
> Gentoo is AMD64 will this cause problems? Should I just do x86 i686 all the
> way around and use CFLAGS to optimize for Opteron?
> It must be extremely stable.

With a 64bit kernel you can avoid the issues that arise with >2G ram on 32bit
platforms (having to choose how to split the 4G address space or use the PAE

You will need to enable CONFIG_IA32_EMULATION to run 32bit guests

You don't have to run a 64bit userland for the host. For the most
platform-compatible setup you can compile 32 and 64bit kernels (crossdev on
gentoo makes this very easy) and choose which to run at boot This allows you
to bring the host and 32bit vservers up on on a 32bit platform if required
(DR situation or whatever). This is assuming that the issues with 32bit
util-vserver tools on a 64bit kernel have been resolved.

I use amd64 gentoo (userland and kernel) for the host and 32 and 64bit gentoo
guests depending on requirements.


Cross-compiling a 64bit kernel on 32bit gentoo:
echo 'PORTDIR_OVERLAY="/usr/local/portage"' >> /etc/make.conf
mkdir /usr/local/portage
emerge sys-devel/crossdev
crossdev -s1 -t x86_64-pc-linux-gnu
cd /usr/src
cp -pr linux-<kernel>-<vserver> linux-<kernel>-<vserver>-x86_64
cd linux-<kernel>-<vserver>-x86_64
make ARCH=x86_64 CROSS_COMPILE=x86_64-pc-linux-gnu- mrproper
make ARCH=x86_64 CROSS_COMPILE=x86_64-pc-linux-gnu- menuconfig
# General Setup ---> Local version - append to kernel release: -x86_64
# Executable file formats / Emulations --->IA32 Emulation
make -j5 ARCH=x86_64 CROSS_COMPILE=x86_64-pc-linux-gnu-
make -j5 ARCH=x86_64 CROSS_COMPILE=x86_64-pc-linux-gnu- modules_install
mount /boot
cp arch/x86_64/boot/bzImage /boot/bzImage-<kernel>-<vserver>-x86_64
vi /boot/grub/grub.conf
...add new 64bit kernel entry

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