root/adm/backup/backup-worker.sh

#!/bin/bash
#
# See Usage().
#
# Feel free to copy and modify.
# --xio

Usage() {
        echo "Usage: $( basename $0 ) {<source_dev_path>} {<target_dir_path>} {<keep_time>} {0|1}"
        echo "Make an incremental backup of a source device to a target directory.  Clean increments older than <Keep time>."
        echo "  \$1: Source device path."
        echo "  \$2: Target backup directory."
        echo "  \$3: Time to keep increments."
        echo "  \$4: Make a snapshot of the device first (for LVM logical volumes).  There should be at least \$snap_size free in LVM logival volume's VG to create the snapshot."
}

# Check if there are exactly 4 argv[] parameters.
CkParm() {
        if [ $# -ne 4 ]; then
                echo " ** E: Wrong parameters number: $#.  Given \$@: $@" 1>&2
                Usage
                exit 1
        fi
}

# Check UID to be root.
CkUID() {
        if [ $UID -ne 0 ]; then
                echo " ** E: UID=0 required.  Current UID=$UID." 1>&2
                exit 1
        fi
}

# Check if the source device exists and OK.
CkDev() {
        if [ ! -b "$1" ]; then
                echo " ** E: $1 is not a block special device file." 1>&2
                Usage
                exit 1
        fi

        if [ "$if_snapshot" -eq 1 ]; then
                if ! lvdisplay "$1" &> /dev/null; then
                        echo " ** E: $1 doesn't look like a LVM LV." 1>&2
                        exit 1
                fi
        fi
}

# Check if snapshot flag is correct (0 or 1).
CkSnapFlag() {
        if ! echo "$1" | grep '1\|0' &> /dev/null; then
                echo " ** E: Snapshot flag can be either 0 or 1.  Given: $1" 1>&2
                exit 1
        fi
}

# Unmount and remove the snapshot.
CleanUp() {
        echo "Cleaning up..."
        umount -v "$source"
        rmdir "$source"
        if [ "$if_snapshot" -eq 1 ]; then
                echo "Removing LVM snapshot $source_backup_dev_path..."
                lvremove -f "$source_backup_dev_path"
        fi
}

# ------------------------------------------------------------------------------

# Path to a source device.
source_dev_path="$1"
# Path to a target directory on a backup media (possibly remote).
target="$2"
# Time period to keep increments.  Default to 1 week.
keep_time="${3:-1W}"
# Make a LVM snapshot?
if_snapshot="$4"

# Checks
CkUID
CkParm $@
CkDev "$source_dev_path"
CkSnapFlag "$if_snapshot"

echo "Backing up $source_dev_path -> $target..."

# Process variables.
if [ "$if_snapshot" -eq 1 ]; then
        source_backup_dev_path="${source_dev_path}_backup"
        snap_size="1G"
else
        source_backup_dev_path="$source_dev_path"
fi
source_backup_name="$(basename $source_backup_dev_path)"
source="/mnt/backup/$source_backup_name"

# Create a snapshot.
if [ "$if_snapshot" -eq 1 ]; then
        if lvcreate -s -L "$snap_size" -n "$source_backup_name" "$source_dev_path"; then
                echo "Snapshot $source_backup_name created for $source_dev_path."
        else
                echo " ** E: Error creating snapshot." 1>&2
                CleanUp
                exit 1
        fi
fi

# Mount.
mkdir -p "$source"
if mount "$source_backup_dev_path" "$source"; then
        echo "Successful mount: $source_backup_dev_path -> $source."
else
        echo " ** E: Unable to mount $source_backup_dev_path to $source." 1>&2
        CleanUp
        exit 1
fi

#exclude="/dev/* /mnt/* /proc/* /sys/* /tmp/* /srv/backup/*"

# FIXME: Do error processing.  Check if a server is reachable in a case of
# remote backup (--test-server).

# Backup.
echo "Starting rdiff-backup..."
rdiff-backup    --remote-schema 'ssh -C -o "StrictHostKeyChecking no" %s rdiff-backup --server' \
                --create-full-path \
                --print-statistics \
                "$source" "$target"

# Remove old increments.
# --force to remove more than two increments a time.
echo "Removing old increments..."
rdiff-backup    --remote-schema 'ssh -C -o "StrictHostKeyChecking no" %s rdiff-backup --server' \
                --remove-older-than "$keep_time" \
                --force \
                "$target"

CleanUp

echo "Done backing up $source_dev_path."