#!/usr/bin/bash
# snapshot-rootfs.sh
# 
# In your /etc/profile, export the following variables
# LVM_VG_ROOTFS=vg0
# LVM_LG_ROOTFS_NAME=rootfs-arch
# LVM_ROOTFS_SNAPSHOT_SZ=10G
source /etc/profile

crash() {
    echo $1;
    exit 1;
}

[ \
  -n "$LVM_VG_ROOTFS" \
  -a -n "$LVM_LG_ROOTFS_NAME" \
  -a -n "$LVM_ROOTFS_SNAPSHOT_SZ" \
] || crash "Missing one of the LVM variables for snapshot-rootfs.sh";

DATE=`date +%Y%m%dT%H%M`

LAST_SNAPSHOT_NAME=`lvs --select "origin = $LVM_LG_ROOTFS_NAME" \
  --noheadings -o "data_percent,lv_name" 2>&1 \
  |sort -n|grep -o '[^[:space:]]\+$'`

echo "The last snapshot's name is : $LAST_SNAPSHOT_NAME. Remove it? (y/n)"

read REMOVE_LAST_SNAPSHOT

[ $REMOVE_LAST_SNAPSHOT = "y" ] && lvremove $LVM_VG_ROOTFS/$LAST_SNAPSHOT_NAME

lvcreate -n $LVM_LG_ROOTFS_NAME-$DATE \
  --snapshot \
  -L $LVM_ROOTFS_SNAPSHOT_SZ $LVM_VG_ROOTFS/$LVM_LG_ROOTFS_NAME