code.delx.au - monosys/blob - bsnap

   1 #!/bin/bash
   2
   3 set -eu
   4
   5 function snap {
   6     unsnap
   7
   8     mkdir -p /a
   9
  10     dispatch snap < /etc/fstab
  11 }
  12
  13 function unsnap {
  14     tac /etc/fstab | dispatch unsnap
  15
  16     if [ -d "/a" ]; then
  17         rmdir /a
  18     fi
  19 }
  20
  21 function dispatch {
  22     local action="" snaptype=""
  23     local dev="" mnt="" fstype="" opts="" dump=""
  24
  25     while read -r dev mnt fstype opts dump pass; do
  26         snaptype="$(get_snaptype "$fstype" "$dump")"
  27         if [ -z "$snaptype" ]; then
  28             continue
  29         fi
  30         action="${1}_${snaptype}"
  31         echo "$action $mnt"
  32         "$action" "$dev" "$mnt" "$opts"
  33     done
  34 }
  35
  36 function get_snaptype {
  37     local fstype="$1" dump="$2"
  38     if [ "$dump" = "1" ]; then
  39         echo bind
  40     elif [ "$dump" = "2" ] && [ "$fstype" = "btrfs" ]; then
  41         echo btrfs
  42     elif [ "$dump" = "2" ]; then
  43         echo lvm
  44     fi
  45 }
  46
  47 function snap_bind {
  48     local mnt="$2"
  49     mount --bind "${mnt}" "/a${mnt}"
  50 }
  51
  52 function unsnap_bind {
  53     local snapmnt="/a$2"
  54     if mountpoint -q "$snapmnt"; then
  55         umount "$snapmnt"
  56     fi
  57 }
  58
  59 function snap_lvm {
  60     local dev="$1" mnt="$2"
  61     local lvname="" vgname=""
  62     read -r lvname vgname _ < <(lvdisplay --noheadings -C "$dev")
  63     echo "snapshot ${vgname}/${lvname}"
  64     lvcreate -L1G --snapshot --name "${lvname}snap" "${vgname}/${lvname}"
  65     mount -o ro "${dev}snap" "/a${mnt}"
  66 }
  67
  68 function unsnap_lvm {
  69     local snapdev="${1}snap"
  70     local snapmnt="/a$2"
  71     if mountpoint -q "$snapmnt"; then
  72         umount "$snapmnt"
  73     fi
  74     if [ -b "$(readlink -f "$snapdev")" ]; then
  75         lvremove -f "${dev}snap"
  76     fi
  77 }
  78
  79 function snap_btrfs {
  80     local mnt="$2" opts="$3" snapdir=""
  81
  82     snapdir="$(get_btrfs_snapshot_dir "$opts" "$mnt")"
  83     btrfs subvolume snapshot "$mnt" "$snapdir"
  84
  85     mount --bind "$snapdir" "/a${mnt}"
  86 }
  87
  88 function unsnap_btrfs {
  89     local mnt="$2" opts="$3" snapdir=""
  90
  91     local snapmnt="/a$2"
  92     if mountpoint -q "$snapmnt"; then
  93         umount "$snapmnt"
  94     fi
  95
  96     snapdir="$(get_btrfs_snapshot_dir "$opts" "$mnt")"
  97     if [ -d "$snapdir" ]; then
  98         btrfs subvolume delete "$snapdir"
  99     fi
 100 }
 101
 102 function get_btrfs_snapshot_dir {
 103     local opts="$1" mnt="$2" subvol=""
 104     subvol="$(echo "$opts" | sed -nE 's/^.*\bsubvol=([^,]+)\b.*$/\1/p')"
 105     if [ -z "$subvol" ]; then
 106         echo "Unknown subvol for mountpoint: $mnt"
 107         exit 1
 108     fi
 109     echo "/$(hostname -s)/${subvol}-snap"
 110 }
 111
 112 if [ "$(id -u)" -ne 0 ]; then
 113     echo "Must be root"
 114     exit 1
 115 fi
 116
 117 if [ "${1:-}" = "off" ]; then
 118     unsnap
 119 elif [ "${1:-}" = "on" ]; then
 120     snap
 121 else
 122     echo "Usage: $0 on|off"
 123     exit 1
 124 fi