rsyc backup using hardlinks

gistfile1.txt

#!/bin/sh
#
# Based on http://www.noah.org/engineering/src/shell/rsync_backup
# Retention count 21 for making 3 backups each day for a week.
#
# This maintains a rotating backup. This will normalize permissions on
# all files and directories on backups. It has happened that someone removed
# owner write permissions on some files, thus breaking the backup process. This
# prevents that from happening. All this permission changing it tedious, but it
# eliminates any doubts. I could have done this with "chmod -R +X", but I
# wanted to explicitly set the permission bits.
#
# Pass two arguments: rsync_backup SOURCE_PATH BACKUP_PATH
#
# $Id: rsync_backup 222 2016-01-21 22:05:30Z noah $

usage() {
    echo "usage: rsync_backup [-v] [-n] SOURCE_PATH BACKUP_PATH"
    echo "    SOURCE_PATH and BACKUP_PATH may be ssh-style remote paths; although,"
    echo "    BACKUP_PATH is usually a local directory where you want the"
    echo "    backup set stored."
    echo "    -v : set verbose mode"
    echo "    -n : normalize directory and file permissions to 755 for dirs and 644 for files."
}

# How many folders to rotate. 21 for 3 backups a day
RETENTION_COUNT=21

VERBOSE=0
NORMALIZE_PERMS=0
while getopts ":vnh" options; do
    echo $options
    case $options in
        v ) VERBOSE=1;;
        n ) NORMALIZE_PERMS=1;;
        h ) usage
            exit 1;;
        \? ) usage
            exit 1;;
        * ) usage
            exit 1;;
    esac
done
shift $(($OPTIND - 1))
SOURCE_PATH=$1
BACKUP_PATH=$2
if [ -z $SOURCE_PATH ] ; then
    echo "Missing argument. Give source path and backup path."
    usage
    exit 1
fi
if [ -z $BACKUP_PATH ] ; then
    echo "Missing argument. Give source path and backup path."
    usage
    exit 1
fi

SOURCE_BASE=`basename $SOURCE_PATH`
PERMS_DIR=755
PERMS_FILE=644
if [ $VERBOSE ]; then
    RSYNC_OPTS="-a --delete -v"
    date
else
    RSYNC_OPTS="-a --delete -q"
fi

if [ ! -d $BACKUP_PATH ] ; then
    mkdir $BACKUP_PATH
fi

COUNTER=$RETENTION_COUNT

while [ $COUNTER -ge 0 ]
do
   if [ ! -d $BACKUP_PATH/$SOURCE_BASE.$COUNTER ] ; then
    mkdir $BACKUP_PATH/$SOURCE_BASE.$COUNTER
   fi
   COUNTER=$(( $COUNTER - 1 ))
done


# TODO All these find operations to clean up permissions is going to add a lot
# of overhead as the backup set gets bigger. At 100 GB it's not a big deal. The
# correct thing would be to have an exception based system where I correct
# permissions when/if they cause a problem.

# Rotate backups.
if [ $NORMALIZE_PERMS -eq 1 ]; then
    if [ $VERBOSE ]; then
        echo "Normalizing file permissions."
    fi
    find $BACKUP_PATH/$SOURCE_BASE.21 -type d -exec chmod $PERMS_DIR {} \;
    find $BACKUP_PATH/$SOURCE_BASE.21 -type f -exec chmod $PERMS_FILE {} \;
fi
rm -rf $BACKUP_PATH/$SOURCE_BASE.$RETENTION_COUNT

COUNTER=$(( $RETENTION_COUNT - 1 ))

while [ $COUNTER -gt 1 ]
do
   PREVIOUS=$(( $COUNTER - 1 ))
   mv     $BACKUP_PATH/$SOURCE_BASE.$PREVIOUS $BACKUP_PATH/$SOURCE_BASE.$COUNTER
   COUNTER=$(( $COUNTER - 1 ))
done

cp -al $BACKUP_PATH/$SOURCE_BASE.0 $BACKUP_PATH/$SOURCE_BASE.1

# Backup.
if [ $NORMALIZE_PERMS -eq 1]; then
    if [ $VERBOSE -eq 1 ]; then
        echo "Normalizing file permissions."
    fi
    find $BACKUP_PATH/$SOURCE_BASE.0 -type d -exec chmod $PERMS_DIR {} \;
    find $BACKUP_PATH/$SOURCE_BASE.0 -type f -exec chmod $PERMS_FILE {} \;
fi
rsync $RSYNC_OPTS $SOURCE_PATH/. $BACKUP_PATH/$SOURCE_BASE.0/.
RSYNC_EXIT_STATUS=$?
if [ $NORMALIZE_PERMS -eq 1 ]; then
    if [ $VERBOSE -eq 1 ]; then
        echo "Normalizing file permissions."
    fi
    find $BACKUP_PATH/$SOURCE_BASE.0 -type d -exec chmod $PERMS_DIR {} \;
    find $BACKUP_PATH/$SOURCE_BASE.0 -type f -exec chmod $PERMS_FILE {} \;
fi

# Ignore error code 24, "rsync warning: some files vanished before they could be transferred".
if [ $RSYNC_EXIT_STATUS -eq 24 ] ; then
    RSYNC_EXIT_STATUS=0
fi


# Create a timestamp file to show when backup process completed successfully.
if [ $RSYNC_EXIT_STATUS -eq 0 ] ; then
    rm -f $BACKUP_PATH/$SOURCE_BASE.0/BACKUP_ERROR
    date > $BACKUP_PATH/$SOURCE_BASE.0/BACKUP_TIMESTAMP
else # Create a timestamp if there was an error.
    rm -f $BACKUP_PATH/$SOURCE_BASE.0/BACKUP_TIMESTAMP
    echo "rsync failed" > $BACKUP_PATH/$SOURCE_BASE.0/BACKUP_ERROR
    date >> $BACKUP_PATH/$SOURCE_BASE.0/BACKUP_ERROR
    echo $RSYNC_EXIT_STATUS >> $BACKUP_PATH/$SOURCE_BASE.0/BACKUP_ERROR
fi

if [ $VERBOSE -eq 1 ]; then
    date
fi

exit $RSYNC_EXIT_STATUS