backup/lvm

   1 #!/bin/sh
   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.$opmode" in
  24 4.snap|2.drop)
  25         ;;
  26 *)
  27         cat >&2 <<'END'
  28 usage: .../lvm snap VARDIR DEV MOUNT
  29        .../lvm drop VARDIR
  30 END
  31         exit 1
  32         ;;
  33 esac
  34
  35
  36 #---------- clean up anything
  37
  38 umount -v "$snmnt" || true
  39 test ! -d "$snmnt" || rmdir -- "$snmnt"
  40
  41 set +e
  42 old_lv_dev="$(readlink $vardir/snap-device)"
  43 rc=$?
  44 set -e
  45
  46 if [ $rc = 0 ]; then
  47         set +e
  48         lvchange    $lvm_lvtools_opts -a n $old_lv_dev
  49         lvremove -f $lvm_lvtools_opts      $old_lv_dev
  50         set -e
  51         rm $vardir/snap-device
  52 fi
  53
  54 if test "$opmode" = drop; then
  55         echo 'lvm snap dropped'
  56         exit 0
  57 fi
  58
  59 #---------- create snapshot
  60
  61 fstype="$(mount | sed -n \
  62  "s,^$device on $mountpoint type \([a-z0-9][a-z0-9]*\) .*,-t \1 ,p")"
  63
  64 if [ -z "$lvm_lvsize_opts" ]; then
  65         df="$(df -k $device)"
  66         blocks="$(printf "%s" "$df" |  sed -n '2,$s,^/dev/[^    ]*[     ][      ]*[0-9][0-9]*[  ][      ]*\([0-9][0-9]*\)[      ].*,\1,p')"
  67         lvm_lvsize_opts="-L $blocks"K
  68 fi
  69
  70 lvpath="$(dirname "$device")/$lvm_lv"
  71
  72 ln -s -- "$lvpath" "$vardir"/snap-device
  73
  74 sync
  75 lvcreate -s \
  76         $lvm_lvtools_opts \
  77         $lvm_lvsize_opts \
  78         -n $lvm_lv \
  79         $lvm_lvcreate_opts "$device" $lvm_lvcreate_args
  80
  81 mkdir -- "$snmnt"
  82 mount -v -r $fstype $lvm_mount_opts "$lvpath" "$snmnt"
  83
  84 echo 'lvm snap activated'