Xen Project 4.5 Release Notes

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Xen Project 4.5.0 was released on January 15, 2015.

Xen Project 4.5.0 is the work of 10 months of development, with 11812 changesets.

Also see Xen Project 4.5 Acknowledgements

xm/xend have been removed

In Xen 4.5, the XM toolstack has been removed and been replaced by XL. XL has been designed to be backwards compatible with existing XM domain configuration files and command line syntax. It is therefore expected that any existing configurations should work with XL with the following exceptions:

  • Arbitrary embedded python is not supported. Therefore it will be necessary to remove any python code from your configuration files.
  • Managed domains (e.g. xm vm-create, xm vm-start etc) are not supported by xl. Other toolstacks which support managed domains are the XAPI toolstack and Libvirt.
  • xl does not support the w! notation to share disks between several DomU's
  • For a complete comparison see XL vs Xend Feature Comparison

The other notable difference is that xl, unlike xend, will not perform any host networking configuration for you. The xend code to reconfigure on startup is extremely fragile, prone to bugs when either distro or Xen are upgraded and rather difficult to debug. Instead xl takes the approach of deferring such network configuration to the distribution configuration tools which are usually well understood and documented. Therefore upon upgrading to xl it is necessary to configure your host networking stack appropriately. Please see Network_Configuration_Examples_(Xen_4.1+) for more details on how to do this.

xl is designed to be compatible with xm, except for the cases listed above. If you find a situation where xl seems to be incompatible, please file a bug report using the process described in Reporting_Bugs_against_Xen_Project.

Also see:

xl Upgrade Checklist

  • Configure your host networking using the configuration tools provided by your distribution. (See: Network_Configuration_Examples_(Xen_4.1+))
  • Remove any python code from domU configuration files.
  • Disable xend startup script (if testing on Xen 4.4 or lower)
  • Use xl command instead of xm

New Feature Highlights

The list of new features can be found on the following page: Xen Project 4.5 Feature List

You can also see an evolution of features on Xen Project Release Features

Documentation is available on Xen Project 4.5 Man Pages

Build Requirements

The default installation prefix has been changed to /usr/local. Previously the default installation prefix was /usr To restore the previous behaviour, specify --prefix=/usr when running ./configure, e.g.:

$ ./configure --prefix=/usr

If you choose to accept the new default then be sure to cleanup any residual bits of the old installation in the old prefix, especially libraries and tools which you might pick up by mistake.

Due to this change it may also now be necessary to run /sbin/ldconfig as root after installing Xen.

Note also that Xen now requires gcc v4.1 or greater.

Known issues

While we did the utmost to get a release out, there are certain fixes which were not complete on time. As such please reference this +section if you are running into trouble.

  • systemd not working with Fedora Core 20, 21 or later (systemctl reports xenstore failing to start).Systemd support is now part of Xen source code. While utmost work has been done to make the systemd files compatible across all the distributions, there might issues when using systemd files from Xen sources. The work-around is to define an mount entry in /etc/fstab as follow:
tmpfs                   /var/lib/xenstored      tmpfs  mode=755,context="system_u:object_r:xenstored_var_lib_t:s0" 0 0