The pre-generated distributions and pre-downloaded netboot installers were just updated. While the primary reason was to add Ubuntu Xenial, there were also the following changes:

• Ping can be used as a non-root user on CentOS 7, Fedora 22, and Fedora 23. These distributions use capabilities rather than setuid to give the proper permissions to non-root users for ping. GNU tar (the default) does not preserve these extended attributes, so we switched to BSD tar which does.
• ext4 is the default file system.
• grub.cfg, needed for grub2, is present on everything other than CentOS 6.
• Ubuntu precise is no longer available as a pre-generated image, but can be installed still using the netboot installer.

As usual, the source can be found at github.