#!/bin/bash
# =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
# 2017-01-06-SRJ
# For information on how this script works, and what it does, read the
# file README in this folder
# =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
#
# suggestion from H. Milz: avoid accidental use of $PATH
unset PATH
#
# =-=-=-=-  System commands used by this script. -=-=-=-=-=-=-=-=
   ID=/usr/bin/id; ECHO=/bin/echo; MOUNT=/bin/mount; RM=/bin/rm;
   MV=/bin/mv; CP=/bin/cp; TOUCH=/bin/touch; RSYNC=/usr/bin/rsync;
   DATE=/bin/date; WC=/usr/bin/wc; CAT=/bin/cat; TAIL=/usr/bin/tail;
   HEAD=/usr/bin/head; GREP=/bin/grep; CHMOD=/bin/chmod

# =-=-=-=-=-=-=- Make sure we're running as root -=-=-=-=-=-=-=-=-=
  if (( `$ID -u` != 0 )); then {
  $ECHO "Sorry, must be root. Exiting..."; exit;
  } fi;
# =-=-=-=-=-=-=-=-=-=- Read in the Variables -=-=-=-=-=-=-=-=-=-=-=
  if  [ ! -e $1 ] ; then {
  $ECHO "No viable config file given."; exit 0
  } fi;
# If we're here, there must be a config file to read, the line below
# reads the variables from that file into this bash environment.
  . $1
# # # Update 2017-01-01 SRJ The line above sources the variables from
# # # the config file into this script - see /Backup/00-System.conf
# # # for more information.

# Make sure that the folder list exists, create it if needed;
  if [ ! -f $SNAPSHOT_RW/Backups ] ; then {
  $ECHO Nothing >> $SNAPSHOT_RW/Backups
  } fi;
# The full name of the oldest snapshot, first line in Backups
  [ $($CAT $SNAPSHOT_RW/Backups | $WC --lines) -ge $NUM_SNAP ] && \
  OLDEST=$($HEAD -1 $SNAPSHOT_RW/Backups) || OLDEST="Nothing"
# The full name of the last snapshot, last line in Backups
        LAST=$($TAIL -1 $SNAPSHOT_RW/Backups)
# The full name of the snapshot for this itteration. (2006-06-22-09-47)
        CURRENT=$SNAPSHOT_RW/$($DATE +%F-%H-%M)
# What time is it, in seconds past the epoch?
        StartTime=$($DATE +%s)
# Hour, minute, second function;
_hms()
{
     local S=${1}     # this S is used only in this sub-routine
     ((h=S/3600))     # fills h with the integer of seconds / 3600
     ((m=S%3600/60))  # fills m with the integer of the modula from above / 60
     ((s=S%60))       # fills s with the integer of seconds / 60
     printf "%02d:%02d:%02d\n" $h $m $s  # print 2 digit zero padded numbers
}

# =-=-=-=-=-=-=-=-=- The script itself. -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
# I stopped mounting and unmounting the filesystem, I now do this by
# hand on an as-needed basis - these backup scripts are now on the
# backup drives themselves.
# Attempt to remount the RO mount point as RW; else abort
#  $MOUNT -o remount,rw $MOUNT_DEVICE $MOUNT_DIR ;
#  if (( $? )); then {
#  $ECHO "Could not remount $MOUNT_DIR read-write"; exit;
#  } fi;
# Creating the snapshot.
# Delete the oldest snapshot, if it exists:

  if [ -e ${OLDEST} ] ; then { $RM -rf ${OLDEST} ;} fi ;

# Delete the last filelist and create a new one with proper permissions.

  if [ -f $FILELIST ] ; then { $RM -f $FILELIST ;} fi ;
  $TOUCH $FILELIST ; $CHMOD 600 $FILELIST

# Rsync from the system into the latest snapshot (notice that rsync
# behaves like cp --remove-destination by default, so the destination is
# unlinked first.  If it were not so, this would copy over the other
# snapshot(s) too!

  RSARGS=" --archive --verbose --delete --delete-excluded --numeric-ids \
  --modify-window=1 --hard-links --one-file-system --acls --xattrs \
  --exclude-from="$EXCLUDES" --link-dest=$LAST/ "

# This is the line that does everything we're doing here...
  $RSYNC $RSARGS $SNAP_DIR $CURRENT >> $FILELIST;

# Add today's snapshot to the list, and remove the oldest;

  $ECHO $CURRENT >> $SNAPSHOT_RW/Backups
  $GREP -v $OLDEST $SNAPSHOT_RW/Backups >>  $SNAPSHOT_RW/$$.tmp
  $MV -f $SNAPSHOT_RW/$$.tmp $SNAPSHOT_RW/Backups
  EndTime=$($DATE +%s) ; ElapsedTime=$(( $EndTime - $StartTime ))
  TimeWellSpent=$( _hms ${ElapsedTime})

# Write out the summary file.
  $HEAD -2 $FILELIST > $SUMMARY;
  $ECHO $(( $($GREP -ve /$ $FILELIST | $WC --lines )-5)) \
  New files backed up. >> $SUMMARY
  $ECHO $OLDEST was removed and $CURRENT was created >> $SUMMARY
  $ECHO Elapsed time: $TimeWellSpent >> $SUMMARY
  $TAIL -3 $FILELIST >> $SUMMARY
  $MV  $FILELIST  $CURRENT

# And thats it for SNAP_DIR. Now remount the RW snapshot mountpoint as RO
#  $MOUNT -o remount,ro $MOUNT_DEVICE $MOUNT_DIR ;
#  if (( $? )); then {
#  $ECHO "Could not remount $MOUNT_DIR readonly"; exit;
#  } fi;