#!/usr/bin/env bash
# Disk and Inode Alert (v1.0.0) - from srvScripts.com
# Source, docs and updates: https://srvscripts.com/scripts/disk-inode-alert/
# Copyright (c) 2026 srvScripts.com. MIT licence: if you copy, share or adapt this script, keep this notice and credit srvScripts.com.
# disk-inode-alert.sh — warn before a filesystem runs out of space or inodes, with growth rate and days-to-full
# https://srvscripts.com/scripts/disk-inode-alert/   License: MIT
#
# Checks every real filesystem (tmpfs, devtmpfs, overlay, squashfs and friends are skipped)
# for block and inode usage. Keeps a tiny state file so each run can report growth since the
# previous run and estimate how many days are left. Over a threshold it lists the largest and
# the most inode-heavy directories on that filesystem.
#   bash disk-inode-alert.sh                          # warn 80%, crit 90%
#   bash disk-inode-alert.sh --warn 85 --crit 95 --days 14
#   bash disk-inode-alert.sh -q --mail ops@example.com  # cron: silent unless there is a problem
# Exit codes: 0 all OK, 1 at least one WARN/CRIT, 2 usage or dependency error.
set -uo pipefail
export LC_ALL=C

WARN=80; CRIT=90; DAYS=7; QUIET=0; MAILTO=""; COLOR=1; SCAN=1; DU_TIMEOUT=60
STATE=/var/lib/srvscripts/disk-inode-alert.state; USE_STATE=1
GROWTH_MIN=3600; BASE_MAX=43200      # growth is measured against a baseline 1h..12h old
SKIP_TYPES="tmpfs devtmpfs overlay squashfs ramfs iso9660 efivarfs nsfs fuse.lxcfs"

usage() {
  cat <<'EOF'
Usage: disk-inode-alert.sh [options]
  --warn PCT         warning threshold for space and inodes (default 80)
  --crit PCT         critical threshold for space and inodes (default 90)
  --days N           also warn when a filesystem is estimated to fill within N days (default 7, 0 = off)
  --state FILE       state file for growth tracking (default /var/lib/srvscripts/disk-inode-alert.state)
  --no-state         do not read or write the state file
  --no-scan          do not run du on filesystems over threshold
  --du-timeout SEC   time limit for each du scan (default 60)
  --mail ADDRESS     mail the report to ADDRESS when there is a problem (needs mail or sendmail)
  -q, --quiet        print nothing when everything is OK
  --no-color         plain output
  -h, --help         this help
EOF
}

need_arg() { [[ $# -ge 2 && -n "$2" ]] || { echo "Option $1 needs a value" >&2; exit 2; }; }
while [[ $# -gt 0 ]]; do
  case "$1" in
    --warn) need_arg "$@"; WARN=$2; shift 2 ;;
    --crit) need_arg "$@"; CRIT=$2; shift 2 ;;
    --days) need_arg "$@"; DAYS=$2; shift 2 ;;
    --state) need_arg "$@"; STATE=$2; shift 2 ;;
    --no-state) USE_STATE=0; shift ;;
    --no-scan) SCAN=0; shift ;;
    --du-timeout) need_arg "$@"; DU_TIMEOUT=$2; shift 2 ;;
    --mail) need_arg "$@"; MAILTO=$2; shift 2 ;;
    -q|--quiet) QUIET=1; shift ;;
    --no-color) COLOR=0; shift ;;
    -h|--help) usage; exit 0 ;;
    *) echo "Unknown option: $1 (try --help)" >&2; exit 2 ;;
  esac
done
for n in "$WARN" "$CRIT" "$DAYS" "$DU_TIMEOUT"; do
  [[ "$n" =~ ^[0-9]+$ ]] || { echo "Thresholds must be whole numbers, got '$n'" >&2; exit 2; }
done
(( WARN < CRIT )) || { echo "--warn ($WARN) must be lower than --crit ($CRIT)" >&2; exit 2; }
command -v df >/dev/null || { echo "df not found" >&2; exit 2; }
[[ -t 1 ]] || COLOR=0

if (( COLOR )); then R=$'\e[31m'; Y=$'\e[33m'; G=$'\e[32m'; N=$'\e[0m'; else R=""; Y=""; G=""; N=""; fi
hr() { printf '\n== %s ==\n' "$*"; }
human() { numfmt --to=iec --suffix=B "$1" 2>/dev/null || echo "${1}B"; }   # takes bytes

# ---- read the previous state: "mount used_kb iused epoch" per line --------------------------
declare -A PREV_USED PREV_IUSED PREV_TS
if (( USE_STATE )) && [[ -r "$STATE" ]]; then
  while read -r m u i t; do
    [[ -n "$m" && "$t" =~ ^[0-9]+$ ]] || continue
    PREV_USED[$m]=$u; PREV_IUSED[$m]=$i; PREV_TS[$m]=$t
  done < "$STATE"
fi

# ---- collect filesystems -----------------------------------------------------------------------
# GNU df --output gives space and inodes in one pass; -x drops pseudo filesystems.
skip_args=()
for t in $SKIP_TYPES; do skip_args+=(-x "$t"); done
NOW=$(date +%s)
declare -a ROWS=()
declare -A SEEN
while read -r src fstype size used avail pcent itotal iused ipcent target; do
  [[ "$size" =~ ^[0-9]+$ ]] && (( size > 0 )) || continue
  [[ "$target" == /home/virtfs/* ]] && continue     # cPanel jailshell bind mounts
  [[ -n "${SEEN[$src]:-}" && "$src" == /dev/* ]] && continue   # same device bind-mounted twice
  SEEN[$src]=1
  ROWS+=("$target|$fstype|$size|$used|$avail|${pcent%\%}|$itotal|$iused|${ipcent%\%}")
done < <(df -k --output=source,fstype,size,used,avail,pcent,itotal,iused,ipcent,target "${skip_args[@]}" 2>/dev/null | tail -n +2)
(( ${#ROWS[@]} )) || { echo "No filesystems returned by df (GNU coreutils df is required)" >&2; exit 2; }

# ---- helpers -------------------------------------------------------------------------------------
level_of() {   # percent -> 0 ok, 1 warn, 2 crit
  local p=$1
  [[ "$p" =~ ^[0-9]+$ ]] || { echo 0; return; }
  if (( p >= CRIT )); then echo 2; elif (( p >= WARN )); then echo 1; else echo 0; fi
}
days_left() {  # free, grown, seconds -> days until full (empty if not growing)
  awk -v f="$1" -v g="$2" -v s="$3" 'BEGIN{ if (g <= 0 || s <= 0) exit; d = f / (g * 86400 / s); printf "%.1f", d }'
}
top_dirs() {   # mount, du-mode(space|inodes)
  local mnt=$1 mode=$2 out rc
  local args=(-x --max-depth=2)
  [[ "$mode" == inodes ]] && args+=(--inodes) || args+=(-k)
  out=$(timeout "$DU_TIMEOUT" du "${args[@]}" "$mnt" 2>/dev/null); rc=$?
  printf '%s\n' "$out" | awk -v m="$mnt" -F'\t' '$2 != m' | sort -rn | head -10 |
    while IFS=$'\t' read -r n path; do
      if [[ "$mode" == inodes ]]; then printf '      %12s  %s\n' "$n" "$path"
      else printf '      %12s  %s\n' "$(human $(( n * 1024 )))" "$path"; fi
    done
  (( rc == 124 )) && printf '      (du stopped after %ss; list is partial — raise --du-timeout)\n' "$DU_TIMEOUT"
}

# ---- report ------------------------------------------------------------------------------------
PROBLEMS=0
declare -a HOT=()
report() {
  local row mnt fstype size used avail pct itot iused ipct lvl ilvl worst status grow gtxt full ifull el ibased
  hr "Filesystems (warn ${WARN}%, crit ${CRIT}%$( (( DAYS )) && printf ', or full within %s days' "$DAYS"))"
  printf '  %-6s %-24s %-11s %8s %8s %6s %7s %12s %9s\n' STATUS MOUNT TYPE SIZE FREE SPACE INODES GROWTH/DAY "FULL IN"
  for row in "${ROWS[@]}"; do
    IFS='|' read -r mnt fstype size used avail pct itot iused ipct <<<"$row"
    lvl=$(level_of "$pct"); ilvl=$(level_of "$ipct")
    worst=$(( lvl > ilvl ? lvl : ilvl ))
    gtxt="-"; full="-"; ibased=0
    # growth needs a baseline at least GROWTH_MIN old, so short spikes do not produce silly estimates
    if [[ -n "${PREV_TS[$mnt]:-}" ]] && (( NOW - PREV_TS[$mnt] >= GROWTH_MIN )); then
      el=$(( NOW - PREV_TS[$mnt] ))
      grow=$(( used - PREV_USED[$mnt] ))          # KB since last run
      gtxt=$(awk -v g="$grow" -v s="$el" 'BEGIN{ d = g * 1024 * 86400 / s; sgn = (d < 0) ? "-" : "+"; if (d < 0) d = -d
        if (g == 0) { printf "0"; exit }; split("B KB MB GB TB", u, " "); i = 1; while (d >= 1024 && i < 5) { d /= 1024; i++ } printf "%s%.1f%s", sgn, d, u[i] }')
      full=$(days_left "$avail" "$grow" "$el")
      if [[ "$itot" =~ ^[0-9]+$ ]] && (( itot > 0 )) && [[ "${PREV_IUSED[$mnt]:-}" =~ ^[0-9]+$ ]]; then
        ifull=$(days_left $(( itot - iused )) $(( iused - PREV_IUSED[$mnt] )) "$el")
        if [[ -n "$ifull" ]] && { [[ -z "$full" ]] || awk -v a="$ifull" -v b="$full" 'BEGIN{exit !(a < b)}'; }; then
          full="$ifull"; ibased=1             # inodes will run out before space
        fi
      fi
      if [[ -n "$full" ]]; then
        (( DAYS > 0 )) && awk -v a="$full" -v d="$DAYS" 'BEGIN{exit !(a < d)}' && (( worst < 1 )) && worst=1
        full="${full}d"; (( ibased )) && full="${full}(i)"
      else
        full="-"
      fi
    fi
    case $worst in
      2) status="${R}CRIT${N}  " ;;
      1) status="${Y}WARN${N}  " ;;
      *) status="${G}OK${N}    " ;;
    esac
    if (( worst > 0 )); then PROBLEMS=$(( PROBLEMS + 1 )); HOT+=("$mnt|$lvl|$ilvl"); fi
    [[ "$ipct" =~ ^[0-9]+$ ]] && ipct="${ipct}%" || ipct="-"     # btrfs/zfs report no inode limit
    printf '  %s %-24s %-11.11s %8s %8s %5s%% %7s %12s %9s\n' "$status" "$mnt" "$fstype" \
      "$(human $(( size * 1024 )))" "$(human $(( avail * 1024 )))" "$pct" "$ipct" "$gtxt" "$full"
  done
  if (( SCAN )) && (( ${#HOT[@]} )); then
    command -v du >/dev/null || { echo "  skipped: du not installed"; return; }
    for row in "${HOT[@]}"; do
      IFS='|' read -r mnt lvl ilvl <<<"$row"
      if (( lvl > 0 )); then hr "Largest directories on $mnt (du -x, depth 2)"; top_dirs "$mnt" space; fi
      if (( ilvl > 0 )); then hr "Most files (inodes) on $mnt (du --inodes, depth 2)"; top_dirs "$mnt" inodes; fi
    done
  fi
}

TMP_OUT=$(mktemp) || exit 2
trap 'rm -f "$TMP_OUT"' EXIT
report > "$TMP_OUT"      # plain redirection, not a pipe: PROBLEMS and HOT stay in this shell

# ---- save state for the next run ----------------------------------------------------------------
if (( USE_STATE )); then
  if mkdir -p "$(dirname "$STATE")" 2>/dev/null && : > "$STATE.tmp" 2>/dev/null; then
    for row in "${ROWS[@]}"; do
      IFS='|' read -r mnt _ _ used _ _ _ iused _ <<<"$row"
      [[ "$mnt" == *" "* ]] && continue      # keep the state file one-record-per-line simple
      if [[ -n "${PREV_TS[$mnt]:-}" ]] && (( NOW - PREV_TS[$mnt] < BASE_MAX )); then
        # keep the older baseline so frequent runs still measure growth over hours, not minutes
        printf '%s %s %s %s\n' "$mnt" "${PREV_USED[$mnt]}" "${PREV_IUSED[$mnt]}" "${PREV_TS[$mnt]}" >> "$STATE.tmp"
      else
        printf '%s %s %s %s\n' "$mnt" "$used" "${iused//-/0}" "$NOW" >> "$STATE.tmp"
      fi
    done
    mv -f "$STATE.tmp" "$STATE"
  else
    echo "  INFO  state not saved: cannot write $STATE (run as root or use --state)" >> "$TMP_OUT"
  fi
fi

if (( PROBLEMS )); then
  printf '\n%d filesystem(s) need attention on %s.\n' "$PROBLEMS" "$(hostname)" >> "$TMP_OUT"
else
  printf '\nAll %d filesystem(s) OK.\n' "${#ROWS[@]}" >> "$TMP_OUT"
fi
if (( ! QUIET || PROBLEMS )); then cat "$TMP_OUT"; fi

# ---- optional mail -------------------------------------------------------------------------------
if [[ -n "$MAILTO" ]] && (( PROBLEMS )); then
  subject="Disk/inode alert on $(hostname): $PROBLEMS filesystem(s)"
  body=$(sed 's/\x1b\[[0-9;]*m//g' "$TMP_OUT")
  if command -v mail >/dev/null; then
    printf '%s\n' "$body" | mail -s "$subject" "$MAILTO" || echo "mail command failed" >&2
  elif [[ -x /usr/sbin/sendmail ]]; then
    printf 'To: %s\nSubject: %s\n\n%s\n' "$MAILTO" "$subject" "$body" | /usr/sbin/sendmail -t || echo "sendmail failed" >&2
  else
    echo "skipped: --mail given but neither mail nor sendmail is installed" >&2
  fi
fi
exit $(( PROBLEMS > 0 ? 1 : 0 ))