code.delx.au - monosys/blob - bsnap/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 mnt="$2"
  61     local lvname="" vgname=""
  62     read -r lvname vgname _ < <(get_lvm_vgname_lvname "${mnt}")
  63
  64     echo "snapshot ${vgname}/${lvname}"
  65     lvcreate -L1G --snapshot --name "${lvname}-snap" "${vgname}/${lvname}"
  66     mount -o ro "/dev/${vgname}/${lvname}-snap" "/a${mnt}"
  67 }
  68
  69 function unsnap_lvm {
  70     local mnt="$2"
  71     local lvname="" vgname=""
  72
  73     if mountpoint -q "/a$mnt"; then
  74         umount "/a$mnt"
  75     fi
  76
  77     read -r lvname vgname _ < <(get_lvm_vgname_lvname "${mnt}")
  78     if lvdisplay "${vgname}/${lvname}-snap" &> /dev/null; then
  79         lvremove -f "${vgname}/${lvname}-snap"
  80     fi
  81 }
  82
  83 function get_lvm_vgname_lvname {
  84     local mnt="$1" subvol=""
  85     lvdisplay --noheadings -C "$(findmnt -n -o source "$mnt")"
  86 }
  87
  88 function snap_btrfs {
  89     local mnt="$2" opts="$3" snapdir=""
  90
  91     snapdir="$(get_btrfs_snapshot_dir "$opts" "$mnt")"
  92     btrfs subvolume snapshot "$mnt" "$snapdir"
  93
  94     mount --bind "$snapdir" "/a${mnt}"
  95 }
  96
  97 function unsnap_btrfs {
  98     local mnt="$2" opts="$3" snapdir=""
  99
 100     local snapmnt="/a$2"
 101     if mountpoint -q "$snapmnt"; then
 102         umount "$snapmnt"
 103     fi
 104
 105     snapdir="$(get_btrfs_snapshot_dir "$opts" "$mnt")"
 106     if [ -d "$snapdir" ]; then
 107         btrfs subvolume delete "$snapdir"
 108     fi
 109 }
 110
 111 function get_btrfs_snapshot_dir {
 112     local opts="$1" mnt="$2" subvol=""
 113     subvol="$(echo "$opts" | sed -nE 's/^.*\bsubvol=([^,]+)\b.*$/\1/p')"
 114     if [ -z "$subvol" ]; then
 115         echo "Unknown subvol for mountpoint: $mnt"
 116         exit 1
 117     fi
 118     echo "/.snapshots/tmp-bsnap-${subvol}"
 119 }
 120
 121 if [ "$(id -u)" -ne 0 ]; then
 122     echo "Must be root"
 123     exit 1
 124 fi
 125
 126 if [ "${1:-}" = "off" ]; then
 127     unsnap
 128 elif [ "${1:-}" = "on" ]; then
 129     snap
 130 else
 131     echo "Usage: $0 on|off"
 132     exit 1
 133 fi