#!/bin/bash

# Copy or move a Logical Volume from one Volume Group to another
# possibly on another machine

if [ -z "$4" ]
then
  echo "Usage: $0 LV fromVG [host:]toVG <copy|keep|move> [nocheck]"
  exit 1
fi

# 1. Make sure LV exists on source VG
# 2. Parse destination VG - if it contains a colon, it means hostname:VG
# 3. Make sure LV does not exist on destination VG
# 4. Get size of source LV
# 5. Create destination LV
# 6. Copy content
# 7. Compare source vs. destination if required
# 8. If match, delete source and any log files

host=
LV=$1
fromVG=$2
toVG=$3
task=$4
check=$5

[ "$toVG" = "${toVG/:}" ] || host="${toVG%%:*}"
[ -n "$host" ] && toVG="${toVG##*:}"

needed="ddrescue lvdisplay diff"
for need in $needed
do
  if ! which $need &>/dev/null
  then
    echo "Sorry, I need $need installed before this can work."
    exit 1
  fi
done

if lvdisplay $fromVG/$LV &>/dev/null
then
  if [ -n "$host" ]
  then
    if ssh $host "lvdisplay $toVG/$LV 2>/dev/null" | grep -q $LV
    then
      echo "Logical Volume $LV already exists in Volume Group $toVG on $host"
      exit 1
    fi
  else
    if lvdisplay $toVG/$LV &>/dev/null
    then
      echo "Logical Volume $LV already exists in Volume Group $toVG"
      exit 1
    fi
  fi


  lvsize=`lvdisplay $fromVG/$LV | grep "Current LE" | tr -s ' ' | cut -d' ' -f4`

  if [ -n "$host" ]
  then
    echo "Creating new LV $LV on destination VG $toVG on $host"
    ssh $host "lvcreate -y -l $lvsize -n $LV $toVG"
    echo "Copying content (be patient)..."
    dd if=/dev/$fromVG/$LV bs=1M | ssh $host dd bs=1M of=/dev/$toVG/$LV
  else
    echo "Creating new LV $LV on destination VG $toVG"
    lvcreate -y -l $lvsize -n $LV $toVG
    echo "Copying content..."
    ddrescue -f /dev/$fromVG/$LV /dev/$toVG/$LV /tmp/$LV.log
  fi
  OK=no
  if [ "$check" = "nocheck" ]
  then
    OK=yes
  else
    if [ -n "$host" ]
    then
      echo "Checking the copy..."
      diff -q <(md5sum /dev/$fromVG/$LV | cut -d' ' -f1) <(ssh $host md5sum /dev/$toVG/$LV | cut -d' ' -f1) && OK=yes
    else
      echo "Checking the copy (this will take approximately as long as the copy did)..."
      diff -q /dev/$fromVG/$LV /dev/$toVG/$LV && OK=yes
    fi
  fi
  if [ "$OK" = "yes" ]
  then
    if [ "$task" = "keep" -o "$task" = "copy" ]
    then
      rm -f /tmp/$LV.log
      echo "$LV successfully copied from $fromVG to $toVG"
      exit 0
    elif [ "$task" = "move" ]
    then
      lvremove -y $fromVG/$LV
      rm -f /tmp/$LV.log
      echo "$LV successfully moved from $fromVG to $toVG"
      exit 0
    else
      echo "$LV successfully copied from $fromVG to $toVG"
      echo "but not sure whether you wanted to delete the original, therefore keeping both."
      exit 0
    fi
  else
    echo "Something went wrong."
    exit 1
  fi
else
  echo "Logical Volume $LV not found in Volume Group $fromVG"
  exit 1
fi