README
======

Bootstrapping Wheezy, Precise or older Releases
-----------------------------------------------

For security reasons (avoid risk to circumvent ASLR), recent kernels
have disabled the vsyscall mapping. Unfortunately older distributions
don't run and hence can't be bootstrapped without it.

To enable trapping and enabling emulate calls into the fixed vsyscall
address mapping and hence to run and bootstrap older Linux
distributions in a chroot (as xen-tools does), you need to add
"vsyscall=emulate" to the kernel commandline, e.g. by adding it to
GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub, then running
"update-grub" afterwards and finally reboot.


Kernel/initrd guessing
----------------------

In xen-tools 3.4-1 a new feature was added which allows using 
backtick expressions in xen-tools.conf.

Using this feature you can improve kernel/initrd guessing by 
changing/adding the following options in xen-tools.conf:

   kernel      = /boot/vmlinuz-`uname -r`
   ramdisk     = /boot/initrd.img-`uname -r`


Upgrading Existing kernel/initrd paths
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The kernel, and initrd, settings which are included in the xen-tools
(either statically or dynamically with `uname -r`) are only applied
when the new guest domains are created.

If you upgrade your kernel you will be left with existing xen
guest domains which :

  -  Have the wrong paths setup in /etc/xen/*.cfg
  -  Have incorrect modules stored within their disk images.

Both of these can be updated via the helper scripts located
in:

   /usr/share/doc/xen-tools/examples/


