#!/bin/bash
# rsyncshot
# Craig Jennings craigmartinjennings@gmail.com
# Inspired by Mike Rubel: http://www.mikerubel.org/computers/rsync_snapshots/

# Debugging

# uncomment next 4 lines for debugging output
# exec 5> >(logger -t $0)
# BASH_XTRACEFD="5"
# PS4='$LINENO: '
# set -x

# Default Locations For Setup
# Modify BACKUPLOCATION to point to the mount point of your backup 

MOUNTPOINT=/media/backup;
SCRIPTLOC=/usr/local/bin/rsyncshot;
DESTINATION=$MOUNTPOINT/$HOSTNAME

INSTALLHOME=/etc/rsyncshot
LOGHOME=/var/log/rsyncshot.log;

INCLUDES="$INSTALLHOME/include.txt";
EXCLUDES="$INSTALLHOME/exclude.txt";

# Sidestep Alias Conflicts
# Copy, move, and rm commands are often aliased to require user input. 
# Using a variable allows us to sidestep this and complete the actions without any interaction. 

CP="/usr/bin/cp"
MV="/usr/bin/mv"
RM="/usr/bin/rm"

# Prevent Overlapping Runs with Flock
FLOCKCHECK="flock -x /tmp/rsyncshot.lock -c"

# Default Cron Job Entries
CRON_H="0 1-23 * * * "; # hourly on minute 0 from 1am to 11pm
CRON_D="0 0 * * 1-6 ";  # daily at midnight, Monday - Saturday
CRON_W="0 0 * * 7 ";    # weekly at midnight on Sundays

# Help Function

help()
{
    printf "\nrsyncshot - compact snapshots on Linux using rsync and hard links.\n\n"
    printf "Usage:\nrsyncshot <name> <number of backups to retain>\n"
    printf "          setup (installs rsyncshot and cron jobs)\n"
    printf "          help  (prints this info)\n"
    printf "Notes:\n"
    printf '%s\n'  "- rsyncshot must be run as root"
    printf '%s\n' "- install and log locations defined in script." 
    printf '%s\n'
}


error()
{
    echo "ERROR: $0: $@" 1>&2;
    echo "See \"rsyncshot help\" for usage."
    exit 1;
}

setup()
{    # copy this file to directory on path and make executable
    $CP -f $0 $SCRIPTLOC
    sudo chmod +x $SCRIPTLOC 
    echo "$0 copied to $SCRIPTLOC and is executable"
    
    # make install home if it doesn't exist;
    if [ ! -d $INSTALLHOME ]; then
	   mkdir -p $INSTALLHOME;
	   echo "Created install home at $INSTALLHOME.";
    fi

    # create includes file and add default entries
    if [ -f $INCLUDES ]; then $RM $INCLUDES; fi
    printf "/home /etc /usr/local/bin" >> $INCLUDES;
    echo "modify include file at $INCLUDES";

    # create excludes file and add default entries
    if [ -f $EXCLUDES ]; then $RM $EXCLUDES; fi
    printf "*.pyc\n*.pyo\n*.class\n*.elc\n*.o\n*.tmp\n.cache*" >>  $EXCLUDES;
    echo "modify exclude file at $EXCLUDES";

    # write out current crontab, append default entries, and install
    crontab -l > crontemp;
    echo "$CRON_H $FLOCKCHECK '$SCRIPTLOC hourly 22 >> $LOGHOME 2>&1'" >> crontemp;
    echo "$CRON_D $FLOCKCHECK '$SCRIPTLOC daily 6 >> $LOGHOME 2>&1'" >> crontemp;
    echo "$CRON_W $FLOCKCHECK '$SCRIPTLOC weekly 51 >> $LOGHOME 2>&1'" >> crontemp;
    crontab crontemp;
    $RM crontemp;
    echo "hourly, daily, and weekly cron jobs installed.";
}

# Display Help If Requested
# Make the argument uppercase for case insensitivity. 

TYPE=$(tr '[a-z]' '[A-Z]' <<< $1);
if [ "$TYPE" = "HELP" ]; then help; exit; fi

# Ensure We're Running As Root

if [ "$EUID" -ne 0 ]; then error "This script must be run as root."; fi

# Display Start Information 

echo "rsyncshot invoked on `date -u` with: $0 $1 $2";

# Validate Backup Type
# First argument must be alpha characters

if ! [[ $1 =~ [a-zA-Z] ]]; then error "snapshot type not recognized."; fi
if [ "$TYPE" = "SETUP" ]; then setup; exit; fi

# Validate Max Snapshots
# Second argument must be numeric

if ! [[ $2 =~ [0-9] ]]; then error "max snapshots not a number."; fi
MAX=$(($2-1));

# Validate Include File (Source Directories) Exist
# Validates the include file exists, and checks the file contents are valid directories

if [ ! -f "$INCLUDES" ]; then error "include file $INCLUDES not found."; fi
SOURCES=$(<$INCLUDES);
for SOURCE in $SOURCES
do
    if [ ! -d "$SOURCE" ]; then error "source $SOURCE not found"; fi
done

# Validate Exclude File (Exclusion Patterns) Exist

if [ ! -f "$EXCLUDES" ]; then error "Exclude file $EXCLUDES not found."; fi

# Validate Mountpoint 
# Fail if mountpoint doesn't exist. 
# Attempt mounting if destination filesystem not mounted; error if attempt fails. 

[ -d $MOUNTPOINT ] || error "$MOUNTPOINT doesn't exist!"

if grep -qs "$MOUNTPOINT" /proc/mounts  ; then
    true
else if  [ $? -eq 0 ]; then 
         true
     else
         error "$MOUNTPOINT unmounted, and mount attempt failed."
     fi
fi

# Validate Destination Directory Exists

[ -d $DESTINATION ] || mkdir $DESTINATION || error "$DESTINATION doesn't exist, and attempt to create failed."

# Sync Each Backup Directory In Turn

for SOURCE in $SOURCES
do
    rsync -avh -i --times \
    	  --delete  --delete-excluded \
    	  --exclude-from=$EXCLUDES \
    	  --update $SOURCE $DESTINATION/latest ;
done

# If Exists, Delete Max+1 Snapshot

if [ -d $DESTINATION/$TYPE.$MAX ]; then
    $RM -rf $DESTINATION/$TYPE.$MAX;
fi

# Rotate Remaining Snapshots Descending

for (( start=$(($MAX)); start>=0; start--)); do
    end=$(($start+1));
	if [ -d $DESTINATION/$TYPE.$start ]; then
	    $MV $DESTINATION/$TYPE.$start $DESTINATION/$TYPE.$end;
	fi
done

# Reset Directory Timestamp

touch $DESTINATION/latest

# Hard Link Only Copy to Destination

$CP -al $DESTINATION/latest $DESTINATION/$TYPE.0;

# Make Directory Type Read-Only

chmod -w $DESTINATION/$TYPE.0

# Print Time and Exit

echo "rsyncshot completed `date -u` ";
exit 0;