mdw@git.distorted.org.uk Git - distorted-backup/blob - snap.ro

   1 #! /bin/sh
   2 ###
   3 ### Make fake snapshots by remounting a filesystem readonly
   4 ###
   5 ### (c) 2011 Mark Wooding
   6 ###
   7
   8 ###----- Licensing notice ---------------------------------------------------
   9 ###
  10 ### This program is free software; you can redistribute it and/or modify
  11 ### it under the terms of the GNU General Public License as published by
  12 ### the Free Software Foundation; either version 2 of the License, or
  13 ### (at your option) any later version.
  14 ###
  15 ### This program is distributed in the hope that it will be useful,
  16 ### but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ### GNU General Public License for more details.
  19 ###
  20 ### You should have received a copy of the GNU General Public License
  21 ### along with this program; if not, write to the Free Software Foundation,
  22 ### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  23
  24 set -e
  25 quis=${0##*/}
  26
  27 ###--------------------------------------------------------------------------
  28 ### Parse the command line.
  29
  30 ## Provide help or version information.
  31 usage="usage: $quis DEVICE [KEY=VALUE ...]"
  32 version="$quis, version 1.0.0"
  33 case "$#,$1" in
  34   0,*) echo >&2 "$usage"; exit 1 ;;
  35   *,-v | *,--version) echo "$version"; exit ;;
  36   *,-h | *,--help)
  37     cat <<EOF
  38 $version
  39 $usage
  40
  41 Option keys:
  42   dir=MOUNTPT           Mount point of filesystem.
  43   op=OPERATION          \`snap' to create snapshot, or \`unsnap' to remove.
  44   tag=TAG               Disambiguation tag to store in filesystem.
  45 EOF
  46     exit
  47     ;;
  48 esac
  49
  50 ## Scan the option keys.
  51 dev=$1; shift
  52 Oop=snap Otag=snap
  53 win=t
  54 for i in "$@"; do
  55   case "$i" in
  56     ?*=*) ;;
  57     *) echo >&2 "$quis: malformed option \`$i'"; exit 1 ;;
  58   esac
  59   k=${i%%=*} v=${i#*=}
  60   case "$k" in *.ro) k=${k%.ro} ;; ?*.?*) continue ;; esac
  61   case "$k" in
  62     op | tag | dir) eval "O$k=\$v" ;;
  63     *) echo >&2 "$quis: unknown option \`$k'"; win=nil ;;
  64   esac
  65 done
  66 case $win in nil) exit 1 ;; esac
  67
  68 ## Find a mount point if none was given.
  69 sdn='s/^b[^ ]*  *[^ ]*  *[^ ]*  *[^ ]*  *\([0-9]*\),  *\([0-9]*\) .*$/\1:\2/'
  70 case "${Odir+t}" in
  71   t) ;;
  72   *)
  73     exec 3</etc/mtab
  74     devno=$(ls -lL "/dev/$dev" | sed "$sdn")
  75     case "$devno" in
  76       *:*) ;;
  77       *) echo >&2 "$quis: $dev is not a block device"; exit 1 ;;
  78     esac
  79     while read <&3 d m fs hunoz; do
  80       if [ ! -b "$d" ]; then continue; fi
  81       dn=$(ls -lL "$d" | sed "$sdn")
  82       case "$dn" in
  83         "$devno")
  84           case "${Odir+t}" in
  85             t) echo >&2 "$quis: /dev/$dev mounted multiple times"; exit 1 ;;
  86           esac
  87           Odir=$m
  88           ;;
  89       esac
  90     done
  91     exec 3>&-
  92     ;;
  93 esac
  94 case "${Odir+t}" in
  95   t) ;; *) echo >&2 "$quis: /dev/$dev apparently not mounted"; exit 1 ;;
  96 esac
  97
  98 ###--------------------------------------------------------------------------
  99 ### Take or remove the snapshot.
 100
 101 case "$Oop" in
 102
 103   snap)
 104     echo "$Otag" >"$Odir/.snap"
 105     mount -oremount,ro "/dev/$dev" "$Odir"
 106     echo "$dev"
 107     ;;
 108
 109   unsnap)
 110     if [ ! -f "$Odir/.snap" ]; then
 111       echo >&2 "$quis: no snapshot tag"
 112       exit 1
 113     fi
 114     read tag <"$Odir/.snap"
 115     case "$tag" in
 116       "$Otag") ;;
 117       *)
 118         echo >&2 "$quis: tag mismatch (found \`$tag' but expected \`$Otag')"
 119         exit 1
 120         ;;
 121     esac
 122     mount -oremount,rw "/dev/$dev" "$Odir"
 123     rm "$Odir/.snap"
 124     ;;
 125
 126   *)
 127     echo >&2 "$quis: unknown operation \`$Oop'"
 128     exit 1
 129     ;;
 130
 131 esac
 132
 133 ###----- That's all, folks --------------------------------------------------