Congratulations, you're on PyGrub!

• Your menu.lst file, the different kernel images in your /boot directory and most importantly, the kernel you're running (an Amazon EC2 version extremely unlikely to be running on a physical host) strongly imply you do have pygrub enabled.
  
  
  
  • This is because non-Pygrub XenPVs must use the same kernel as the host
  
  


• The oddly empty dmesg is likely a side-effect of the customizations in the EC2 kernel; compare with the very informative output of a normal kernel on a XenPV 3.4

A little bit on XenPV kernel options:

• Your current custom EC2 kernel boots with the options root=/dev/sda1 xencons=tty (see end of menu.lst)


• The standard XenPV boot options on stock kernels, instead are root=/dev/xvda1 console=hvc0
  
  
  
  • xvda is the paravirtualized (and more efficient) disk device, while sda is the less efficient emulated device -- this is the first time I've seen the latter used in a 3.x XenPV.
  
  
  • xencons=tty and console=hvc0 are very similar, but I believe the former is an older (legacy) usage; you can stack them with no ill-effects; it simply tells the kernel that the standard virtual terminal is unavailable for the console, and to use the specialized hvc0 device instead.
  
  

How to switch kernels:

This part may be slightly hairy, and you should be in your provider's good books because you may need their help with a simple cp operation once or twice! After that, you'll know what options you need and should be set for the future.

• To give you some context if you need it, here are some files from my XenPV VPS on the latest 64-bit kernel: ls -l /boot, menu.lst and a full post-boot dmesg



• Add the following at the top of your menu.lst, adapting to the kernel version you need:

  
  
  

  
  
  default=0
  
  title vmlinuz-3.2.0-25-generic
  
  root            (hd0) 
  
  kernel          /boot/vmlinuz-3.2.0-25-generic ro root=/dev/sda1 xencons=tty console=hvc0
  
  initrd      /boot/initrd.img-3.2.0-25-generic
  
  




• Cross your fingers, reboot, and hope it comes back up!



• If not, try changing to root=/dev/xvda1 and that should almost certainly work.


• Remember to decline installing "new" menu.lst when upgrading kernels!