monthly-backup-incremental.sh

   1 #!/bin/sh
   2 # Copyright (C) 2012  rofl0r
   3
   4 # This program is free software; you can redistribute it and/or modify
   5 # it under the terms of the GNU General Public License as published by
   6 # the Free Software Foundation; either version 2 of the License, or
   7 # (at your option) any later version.
   8
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU General Public License for more details.
  13
  14 # You should have received a copy of the GNU General Public License along
  15 # with this program; if not, write to the Free Software Foundation, Inc.,
  16 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17
  18 # this program will use 2 directories for backups
  19 # month0 and month1
  20 # the current month is taken and modulo 2 applied. so for example
  21 # if the month is march, 3 % 2 == 1, the backup will be placed in
  22 # month1 directory.
  23 # inside this directory, a file "backup.month" will be checked
  24 # if the content is equal to the current month, 3 in our case,
  25 # a normal "daily" backup will be created. if not, the contents of the
  26 # directory will be trashed, and a "full" backup initiated.
  27 # the full backup is an exact copy of the source folder, and will be placed
  28 # in a directory called "full"
  29 # the daily backup will compare the source folder with the full backup
  30 # and put the differences inside a folder "dayXX", where XX is equivalent
  31 # to the number of the day. i.e. 13 if launched on march 13th.
  32 # the daily backup will contain all files changed or added since the last
  33 # full backup.
  34
  35 # using this strategy will lead to an incremental backup covering at least
  36 # one entire month, and maximum 2 months - 1 day.
  37 # given a relatively static set of data, this should take 2-3 times the size
  38 # of the source directory.
  39
  40 # if you want to cover more than 2 months, just change the variable
  41 # month_cycles accordingly (either 2,3,4,6 or 12 make sense).
  42 # be aware that changing this variable will possibly overwrite existing
  43 # backups.
  44
  45 backup_source=/srv/
  46 backup_root=/mnt/backup/
  47 filesync_cmd=filesync
  48 month_cycles=2
  49
  50 month=`date +%m`
  51 day=`date +%d`
  52 month_mod=`expr $month % $month_cycles`
  53 backup_dir="${backup_root}/month${month_mod}/"
  54 backup_full="${backup_dir}/full/"
  55 backup_day="${backup_dir}/day${day}/"
  56 backup_cfg="${backup_dir}/backup.month"
  57 log_dir="${backup_dir}/logs/"
  58
  59 do_backup_full() {
  60         rm -rf "$backup_full"
  61         rm -rf "${backup_dir}/day*"
  62         rm -rf "${log_dir}/*"
  63         echo $month > "$backup_cfg"
  64         # we write to a logfile to prevent getting the stdout mailed by cron
  65         # which would mean megabytes per run on a big number of files
  66         # this way the logs will be cleared together with the data after
  67         # completion of a cycle.
  68         logfile="${log_dir}/full.log"
  69         "$filesync_cmd" -e -d -f "$backup_source" "$backup_full" > "$logfile"
  70 }
  71
  72 do_backup_daily() {
  73         logfile="${log_dir}/day${day}.log"
  74         "$filesync_cmd" -e -d -f "$backup_source" "$backup_full" "$backup_day" > "$logfile"
  75 }
  76
  77
  78 mkdir -p "${backup_dir}" "${log_dir}" || (echo failed to create directory structure; exit 1)
  79
  80 if [ -e "$backup_cfg" ] ; then
  81         cont=`cat "$backup_cfg"`
  82         if [ "$cont" = "$month" ] ; then
  83                 do_backup_daily
  84         else
  85                 do_backup_full
  86         fi
  87 else
  88         do_backup_full
  89 fi