| 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 -------------------------------------------------- |