backup/lvm

   1 #!/bin/bash
   2 # invoked by backup scripts as
   3 #    lvm snap $vardir $device $mountpoint
   4 #               creates and mounts on $vardir/snap-mount
   5 #               creates $vardir/snap-device -> device
   6 #    lvm drop $vardir
   7
   8 set -e
   9
  10 nargs=$#
  11 opmode="$1"
  12 vardir="$2"
  13 device="$3"
  14 mountpoint="$4"
  15
  16 lvm_lv=chiark-backup
  17 lvm_lvtools_opts='-A n'
  18 lvm_lvcreate_opts=
  19 lvm_lvcreate_args=
  20
  21 test ! -f /etc/chiark-backup/settings.sh || . /etc/chiark-backup/settings.sh
  22
  23 case "$nargs.$opmode" in
  24 4.snap|2.drop)
  25         ;;
  26 *)
  27         cat >&2 <<'END'
  28 usage: .../lvm snap VARDIR DEV MOUNT
  29        .../lvm drop VARDIR
  30 END
  31         exit 1
  32         ;;
  33 esac
  34
  35
  36 #---------- clean up anything
  37
  38 snmnt="$vardir/snap-mount"
  39 umount -v "$snmnt" || true
  40 test ! -d "$snmnt" || rmdir -- "$snmnt"
  41
  42 set +e
  43 old_lv_dev="$(readlink $vardir/snap-device)"
  44 rc=$?
  45 set -e
  46
  47 if [ $rc = 0 ]; then
  48         set +e
  49         lvchange    $lvm_lvtools_opts -a n $old_lv_dev
  50         lvremove -f $lvm_lvtools_opts      $old_lv_dev
  51         set -e
  52         rm $vardir/snap-device
  53 fi
  54
  55 if test "$opmode" = drop; then
  56         echo 'lvm snap dropped'
  57         exit 0
  58 fi
  59
  60 #---------- create snapshot
  61
  62 fstype="$(mount | sed -n \
  63  "s,^$device on $mountpoint type \([a-z0-9][a-z0-9]*\) .*,-t \1 ,p")"
  64
  65 if [ -z "$lvm_lvsize_opts" ]; then
  66         vggroup="${device#/dev/}"
  67         vggroup="${vggroup%/*}"
  68         vgdisplay_out="$(really vgdisplay -c "$vggroup")"
  69         extents="$(printf "%s" "$vgdisplay_out" | awk -F: '{print $16}')"
  70         lvm_lvsize_opts="-l $extents"
  71 fi
  72
  73 lvpath="$(dirname "$device")/$lvm_lv"
  74
  75 ln -s -- "$lvpath" "$vardir"/snap-device
  76
  77 sync
  78 lvcreate -s \
  79         $lvm_lvtools_opts \
  80         $lvm_lvsize_opts \
  81         -n $lvm_lv \
  82         $lvm_lvcreate_opts "$device" $lvm_lvcreate_args
  83
  84 mkdir -- "$snmnt"
  85 mount -v -r $fstype $lvm_mount_opts "$lvpath" "$snmnt"
  86
  87 echo 'lvm snap activated'