Shows Vdev->block device mappings for a Xen guest

list-vm-disks.sh

#!/bin/bash

# Written in 2018 by Gerdriaan Mulder <hello[at]moeilijklastig(dot)nl>

# This tool shows the mapping between a Xen Vdev attached to a Xen guest.
# Example output that uses an LVM backend:
#
#  # ./list-vm-disks myguest
#  Domain -> ID: myguest -> 42
#  Listing Vdev -> LV mappings...
#  
#  Vdev 51714 -> /dev/vpsdisks/myguest.myhostna.me-disk
#  Vdev 51713 -> /dev/vpsdisks/myguest.myhostna.me-swap
#  Vdev 51729 -> /dev/vpsdisks/myoldguest.myhostna.me-disk

print_usage() {
        echo "Usage: $0 [-h|--help] <domain>"
        echo ''
        echo '<domain>          A (unique part of a) domain name to examine'
        echo ''
        echo 'This tool shows a mapping between a Xen Vdev (as returned by'
        echo '`xl block-list <domain-id>` and the attached block device, which'
        echo 'is usually an LVM logical volume.'
        echo ''
        echo 'The Vdev number can then be fed to a tool like `xl block-detach`:'
        echo '`xl block-detach <domain-id> <Vdev>`; this removes the block'
        echo 'device from <domain-id>.'
        echo ''
        echo 'Attaching a block device can be done like:'
        echo '`xl block-attach <domain-name> "phy:/path/to/lvm/disk,xvdX,<r|w>"`'
}

ARGC="$#"
DOMNAME="$1"

if [[ ! "$ARGC" -eq 1 ]]; then
        print_usage
        exit 0;
elif [[ "$ARGC" -eq 1 && "${DOMNAME:0:1}" == "-" ]]; then
        print_usage
        exit 0;
fi

DOMID="`xl list | grep ${DOMNAME} | tail -n 1 | awk '{print $2}'`"

echo "Domain -> ID: $DOMNAME -> $DOMID"
echo "Listing Vdev -> LV mappings..."
echo ''

VDEVS="`xl block-list ${DOMID} | tail -n +2 | awk '{print $1}'`"

for j in ${VDEVS}; do
        LV="`xenstore-read /local/domain/0/backend/vbd/${DOMID}/${j}/params`"
        echo "Vdev $j -> $LV"
done