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 file is part of the distorted.org.uk backup suite.
  11 ###
  12 ### distorted-backup is free software; you can redistribute it and/or modify
  13 ### it under the terms of the GNU General Public License as published by
  14 ### the Free Software Foundation; either version 2 of the License, or
  15 ### (at your option) any later version.
  16 ###
  17 ### distorted-backup is distributed in the hope that it will be useful,
  18 ### but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ### GNU General Public License for more details.
  21 ###
  22 ### You should have received a copy of the GNU General Public License along
  23 ### with distorted-backup; if not, write to the Free Software Foundation,
  24 ### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25
  26 set -e
  27 quis=${0##*/}
  28
  29 ###--------------------------------------------------------------------------
  30 ### Parse the command line.
  31
  32 ## Provide help or version information.
  33 usage="usage: $quis DEVICE [KEY=VALUE ...]"
  34 version="$quis, version 1.0.0"
  35 case "$#,$1" in
  36   0,*) echo >&2 "$usage"; exit 1 ;;
  37   *,-v | *,--version) echo "$version"; exit ;;
  38   *,-h | *,--help)
  39     cat <<EOF
  40 $version
  41 $usage
  42
  43 Option keys:
  44   dir=MOUNTPT           Mount point of filesystem.
  45   op=OPERATION          \`snap' to create snapshot, or \`unsnap' to remove.
  46   tag=TAG               Disambiguation tag to store in filesystem.
  47 EOF
  48     exit
  49     ;;
  50 esac
  51
  52 ## Scan the option keys.
  53 dev=$1; shift
  54 Oop=snap Otag=snap
  55 win=t
  56 for i in "$@"; do
  57   case "$i" in
  58     ?*=*) ;;
  59     *) echo >&2 "$quis: malformed option \`$i'"; exit 1 ;;
  60   esac
  61   k=${i%%=*} v=${i#*=}
  62   case "$k" in *.ro) k=${k%.ro} ;; ?*.?*) continue ;; esac
  63   case "$k" in
  64     op | tag | dir) eval "O$k=\$v" ;;
  65     *) echo >&2 "$quis: unknown option \`$k'"; win=nil ;;
  66   esac
  67 done
  68 case $win in nil) exit 1 ;; esac
  69
  70 ## Find a mount point if none was given.
  71 sdn='s/^b[^ ]*  *[^ ]*  *[^ ]*  *[^ ]*  *\([0-9]*\),  *\([0-9]*\) .*$/\1:\2/'
  72 case "${Odir+t}" in
  73   t) ;;
  74   *)
  75     exec 3</etc/mtab
  76     devno=$(ls -lL "/dev/$dev" | sed "$sdn")
  77     case "$devno" in
  78       *:*) ;;
  79       *) echo >&2 "$quis: $dev is not a block device"; exit 1 ;;
  80     esac
  81     while read <&3 d m fs hunoz; do
  82       if [ ! -b "$d" ]; then continue; fi
  83       dn=$(ls -lL "$d" | sed "$sdn")
  84       case "$dn" in
  85         "$devno")
  86           case "${Odir+t}" in
  87             t) echo >&2 "$quis: /dev/$dev mounted multiple times"; exit 1 ;;
  88           esac
  89           Odir=$m
  90           ;;
  91       esac
  92     done
  93     exec 3>&-
  94     ;;
  95 esac
  96 case "${Odir+t}" in
  97   t) ;; *) echo >&2 "$quis: /dev/$dev apparently not mounted"; exit 1 ;;
  98 esac
  99
 100 ###--------------------------------------------------------------------------
 101 ### Take or remove the snapshot.
 102
 103 case "$Oop" in
 104
 105   snap)
 106     echo "$Otag" >"$Odir/.snap"
 107     mount -oremount,ro "/dev/$dev" "$Odir"
 108     echo "$dev"
 109     ;;
 110
 111   unsnap)
 112     if [ ! -f "$Odir/.snap" ]; then
 113       echo >&2 "$quis: no snapshot tag"
 114       exit 1
 115     fi
 116     read tag <"$Odir/.snap"
 117     case "$tag" in
 118       "$Otag") ;;
 119       *)
 120         echo >&2 "$quis: tag mismatch (found \`$tag' but expected \`$Otag')"
 121         exit 1
 122         ;;
 123     esac
 124     mount -oremount,rw "/dev/$dev" "$Odir"
 125     rm "$Odir/.snap"
 126     ;;
 127
 128   *)
 129     echo >&2 "$quis: unknown operation \`$Oop'"
 130     exit 1
 131     ;;
 132
 133 esac
 134
 135 ###----- That's all, folks --------------------------------------------------