btrfs/mksnapshot/btrfs-mksnapshot

   1 #!/bin/bash
   2 #
   3 # btrfs-mksnapshot -- Make snapshots of btrfs filesystems
   4 # Copyright (c)2013-2020 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 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=$VOLUME_PATH"
  50
  51 # Detect btrfs filesystem
  52 FS_NAME=$(btrfs filesystem show -m "$VOLUME_PATH" 2>/dev/null | head -1 | cut -d"'" -f2)
  53 if [ -z "$FS_NAME" ]; then
  54         echo "$NAME: Failed to detect btrfs filesystem label for \"$VOLUME_PATH\"!"
  55         exit 1
  56 fi
  57
  58 [ -z "$DRY_RUN" ] || echo "FS_NAME=$FS_NAME"
  59
  60 # Detect btrfs subvolume name
  61 VOLUME_NAME=$(findmnt -nf -o source "$VOLUME_PATH" | grep -F '[' | sed -r 's|^.*\[/(.*)\]|\1|')
  62 if [ -z "$VOLUME_NAME" ] && [ "$VOLUME_PATH" = "/" ]; then
  63         VOLUME_NAME=$(btrfs subvolume get-default / | cut -d' ' -f9)
  64 fi
  65 if [ -z "$VOLUME_NAME" ]; then
  66         echo "$NAME: Failed to detect btrfs subvolume name for \"$VOLUME_PATH\"!"
  67         exit 1
  68 fi
  69 BASE_VOLUME_NAME=$(echo "$VOLUME_NAME" | cut -d'@' -f1)
  70
  71 if [ -n "$DRY_RUN" ]; then
  72         echo "VOLUME_NAME=$VOLUME_NAME"
  73         echo "BASE_VOLUME_NAME=$BASE_VOLUME_NAME"
  74 fi
  75
  76 # Detect mount point of the whole btrfs filesystem
  77 FS_MOUNT_PATH="/media/$FS_NAME"
  78 if [ ! -d "$FS_MOUNT_PATH" ]; then
  79         echo "$NAME: Directory \"$FS_MOUNT_PATH\" does not exist!"
  80         exit 1
  81 fi
  82 if ! grep -q " $FS_MOUNT_PATH btrfs " /proc/mounts; then
  83         echo "$NAME: btrfs \"$FS_NAME\" seems not to be mounted on \"$FS_MOUNT_PATH\"!"
  84         exit 1
  85 fi
  86
  87 [ -z "$DRY_RUN" ] || echo "FS_MOUNT_PATH=$FS_MOUNT_PATH"
  88
  89 # Generate snapshot name
  90 i=1
  91 date=$(date +%Y%m%d)
  92 while true; do
  93         id="$date-$i"
  94         [ -e "$FS_MOUNT_PATH/$BASE_VOLUME_NAME@$id" ] || break
  95         if [ -n "$ONLY_ONE_PER_DAY" ]; then
  96                 echo "Snapshot \"$BASE_VOLUME_NAME@$id\" of \"$VOLUME_PATH\" (\"$VOLUME_NAME\") in btrfs \"$FS_NAME\" already exists."
  97                 exit 0
  98         fi
  99         i=$((i + 1))
 100 done
 101 NEW_VOLUME_NAME="$BASE_VOLUME_NAME@$id"
 102
 103 [ -z "$DRY_RUN" ] || echo "NEW_VOLUME_NAME=$NEW_VOLUME_NAME"
 104
 105 [ -z "$DRY_RUN" ] || exit 0
 106
 107 echo "Creating snapshot of \"$VOLUME_PATH\" (\"$VOLUME_NAME\") in btrfs \"$FS_NAME\" ..."
 108 set -x
 109
 110 cd "$FS_MOUNT_PATH" || exit 1
 111 btrfs subvolume snapshot -r "$VOLUME_NAME" "$NEW_VOLUME_NAME"
 112 find . -maxdepth 1 \( -name "$BASE_VOLUME_NAME" -o \
 113  -name "$BASE_VOLUME_NAME"@'*' \) -exec ls -1d {} \; | sort | column