btrfs/mksnapshot/btrfs-mksnapshot

   1 #!/bin/bash -e
   2 #
   3 # btrfs-mksnapshot -- Make snapshots of btrfs filesystems
   4 # Copyright (c)2013-2014 Alexander Barton (alex@barton.de)
   5 #
   6 # This program is free software; you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation; either version 2 of the License, or
   9 # (at your option) any later version.
  10 #
  11
  12 NAME=`basename "$0"`
  13
  14 function Usage()
  15 {
  16         echo "Usage: $NAME [-1] [<path>]"; echo
  17         echo " -1      Create only one shapshot per day."
  18         echo " -n      Dry run, perform a trial run with no changes made."
  19         echo " <path>  Volume root path (default: \"/\")."
  20         echo; exit 1
  21 }
  22
  23 ONLY_ONE_PER_DAY=
  24 DRY_RUN=
  25
  26 while [ $# -ge 1 ]; do
  27         case "$1" in
  28           [^\-]*)
  29                 break
  30                 ;;
  31           -1)
  32                 ONLY_ONE_PER_DAY=1
  33                 ;;
  34           -n)
  35                 DRY_RUN=1
  36                 ;;
  37           *)
  38                 Usage
  39         esac
  40         shift
  41 done
  42 [ $# -gt 1 ] && Usage
  43
  44 [ -z "$DRY_RUN" ] || echo "ONLY_ONE_PER_DAY=$ONLY_ONE_PER_DAY"
  45
  46 # The subvolume to snapshot, "/" by default
  47 [ $# -ge 1 ] && VOLUME_PATH="$1" || VOLUME_PATH="/"
  48
  49 [ -z "$DRY_RUN" ] || echo "VOLUME_PATH=$VOLUME_PATH"
  50
  51 # Detect btrfs filesystem
  52 FS_NAME=`grep " btrfs " /etc/fstab \
  53         | grep "^LABEL=" \
  54         | grep " $VOLUME_PATH " \
  55         | cut -d'"' -f2 \
  56         | cut -d'=' -f2- \
  57         | cut -d' ' -f1`
  58 if [ -z "$FS_NAME" ]; then
  59         echo "$NAME: Failed to detect btrfs filesystem label for \"$VOLUME_PATH\"!"
  60         exit 1
  61 fi
  62
  63 [ -z "$DRY_RUN" ] || echo "FS_NAME=$FS_NAME"
  64
  65 # Detect btrfs subvolume name
  66 VOLUME_NAME=`grep " btrfs " /etc/fstab \
  67         | grep "subvol=" \
  68         | grep " $VOLUME_PATH " \
  69         | sed -r 's|.*subvol=([[:alnum:]]*).*|\1|'`
  70 if [ -z "$VOLUME_NAME" -a "$VOLUME_PATH" = "/" ]; then
  71         VOLUME_NAME=`btrfs subvolume get-default / | cut -d' ' -f9`
  72 fi
  73 if [ -z "$VOLUME_NAME" ]; then
  74         echo "$NAME: Failed to detect btrfs subvolume name for \"$VOLUME_PATH\"!"
  75         exit 1
  76 fi
  77 BASE_VOLUME_NAME=`echo "$VOLUME_NAME" | cut -d'@' -f1`
  78
  79 if [ -n "$DRY_RUN" ]; then
  80         echo "VOLUME_NAME=$VOLUME_NAME"
  81         echo "BASE_VOLUME_NAME=$BASE_VOLUME_NAME"
  82 fi
  83
  84 # Detect mount point of the whole btrfs filesystem
  85 FS_MOUNT_PATH="/media/$FS_NAME"
  86 if [ ! -d "$FS_MOUNT_PATH" ]; then
  87         echo "$NAME: Directory \"$FS_MOUNT_PATH\" does not exist!"
  88         exit 1
  89 fi
  90 grep " btrfs " /proc/mounts | grep " $FS_MOUNT_PATH " >/dev/null 2>&1
  91 if [ $? -ne 0 ]; then
  92         echo "$NAME: btrfs \"$FS_NAME\" seems not to be mounted on \"$FS_MOUNT_PATH\"!"
  93         exit 1
  94 fi
  95
  96 [ -z "$DRY_RUN" ] || echo "FS_MOUNT_PATH=$FS_MOUNT_PATH"
  97
  98 # Generate snapshot name
  99 i=1
 100 date=`date +%Y%m%d`
 101 while true; do
 102         id="$date-$i"
 103         [ -e "$FS_MOUNT_PATH/$BASE_VOLUME_NAME@$id" ] || break
 104         if [ -n "$ONLY_ONE_PER_DAY" ]; then
 105                 echo "Snapshot \"$BASE_VOLUME_NAME@$id\" of \"$VOLUME_PATH\" (\"$VOLUME_NAME\") in btrfs \"$FS_NAME\" already exists."
 106                 exit 0
 107         fi
 108         i=`expr $i + 1`
 109 done
 110 NEW_VOLUME_NAME="$BASE_VOLUME_NAME@$id"
 111
 112 [ -z "$DRY_RUN" ] || echo "NEW_VOLUME_NAME=$NEW_VOLUME_NAME"
 113
 114 [ -z "$DRY_RUN" ] || exit 0
 115
 116 echo "Creating snapshot of \"$VOLUME_PATH\" (\"$VOLUME_NAME\") in btrfs \"$FS_NAME\" ..."
 117 set -x
 118
 119 cd "$FS_MOUNT_PATH"
 120 btrfs subvolume snapshot "$VOLUME_NAME" "$NEW_VOLUME_NAME"
 121 find . -maxdepth 1 \( -name "$BASE_VOLUME_NAME" -o \
 122  -name "$BASE_VOLUME_NAME"@'*' \) -exec ls -1d {} \; | sort | column