Archive for the ‘Virtualization’ Category

Zombie Disk Image is Loopback-Mounted in a Guest Domain and can’t be Mounted

Chances are if you’re reading this you’ve just pulled yourself out of a xend crash or a similar event which has left one or more zombie VM disk images attached to their loop device. You’re trying to restart the VM but you keep getting this message:

Error: Device 2049 (vbd) could not be connected.
File /xen/vm/disk.img is loopback-mounted through /dev/loop/5,
which is mounted in a guest domain,
and so cannot be mounted now.

losetup will only tell you what you already know:

# losetup -d /dev/loop/5
loop: can't delete device /dev/loop/5: Device or resource busy

If you don’t know the ID number of the VM before it tanked you can find it in your xend logs. Execute this command to free the loop device:

# xenstore-rm backend/vbd/{VM ID}

Download: 32 & 64-bit Xen Paravirtualized domU initrd-free Monolithic Kernel 3.10.17

This is a significant step up from the drop-in kernels I have posted previously. Thanks to a massive cleanup this is the first Xen PV kernel I’ve been able to build with heap randomization and stack smashing protection. Other improvements include:

  • EXT4 support
  • NFS4 support
  • Full-range IPSec support (untested)
  • Head-to-toe netfilter and crypto
  • Per-process i/o stats (see iotop)!
  • dmesg_restrict

kernel-domU-3.10.17-32 739ca0128e68b33164fdccc66bd53bb8 (.config)
kernel-domU-3.10.17-64 0e59bba671893715b04a16f7ee8edb3a (.config)

As always, these kernels are monolithic (lack loadable module support) for security and do not require an initrd to boot a Xen virtual machine.

Your udev or other parts of userland may require upgrading or downgrading to play ball with this kernel version. I’m migrating from 3.2.12 without any issues.

Compiled from gentoo-sources-3.10.17

Proving your Ship is Sinking to


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