Another piece of Bash forgery that automates a common administrative task: creating image-style (i.e. full) backups of logical volumes. The name is a combination of LVM, Snapshot and Backup.
The advantage compared to plain dd is that image contents are
guaranteed to be consistent (at least as consistent as a power fault
would leave disks), no matter how long the actual imaging process takes.
By default lvsnackup uses
LZO
compression in order to benefit from zeroed blocks without slowing down
too much.
Configuration
lvsnackup is configurable using the following environment variables:
CMD_COMPR: compression command (default:lzop -c)COMPR_EXT: image file suffix (default: .lzo)SNAP_SIZE: size of temporary change buffer (default: 1 GB)
Requirements
- lvm (obviously)
- lzop as default compressor
- pv (Pipe Viewer, optional) for visual progress information
For Arch that's
$ pacman -S lvm lzop pv
Usage
$ lvsnackup /dev/vg0/root /mnt/backup/vg0-lvroot.img
Code
#!/bin/bash
# lvsnackup: Create LV Backups using LVM Snapshots
# 2015 Alexander Koch
# defaults
CMD_COMPR="${CMD_COMPR:-"lzop -c"}"
SNAP_SIZE="${SNAP_SIZE:-"1G"}"
COMPR_EXT="${COMPR_EXT:-".lzo"}"
if ! [ $# -eq 2 ]; then
echo "error: invalid arguments."
echo "usage: $0 VOLUME IMAGE"
echo " VOLUME: path to logical volume to backup"
echo " IMAGE: path to image, excl. compression suffix"
exit 1
fi
SRC="$1"
DST="${2}${COMPR_EXT}"
SNAP="$(basename "$SRC")-snap"
SNAP_FULL="$(dirname "$SRC")/$SNAP"
if ! [ -e "$SRC" ]; then
echo "error: invalid volume: '$SRC'."
exit 1
fi
if ! [ -w "$DST" ] && ! [ -w "$(dirname "$DST")" ]; then
echo "error: unable to write to '$DST'."
exit 1
fi
ERR=0
# create snapshot volume
lvcreate -n "$SNAP" -L $SNAP_SIZE -s "$SRC" || exit 1
# compress contents to image
if tty -s && which pv &>/dev/null; then
pv "$SNAP_FULL" | $CMD_COMPR > "$DST" || ERR=1
else
$CMD_COMPR < "$SNAP_FULL" > "$DST" || ERR=1
fi
# destroy snapshot volume
lvremove -f "$SNAP_FULL" || ERR=1
exit $ERR
Update 2015-09-03: Fixed lvremove call