Add initial Linux operations Bash toolkit with network diagnostics

2026-05-05 21:26:02 +00:00
parent 0a242e82b7
commit 9fb291f834
6 changed files with 437 additions and 0 deletions
@@ -0,0 +1,148 @@
+#!/usr/bin/env bash
+set -o errexit
+set -o nounset
+set -o pipefail
+
+target="${1:-}"
+status=0
+warnings=()
+criticals=()
+
+section() {
+  printf '\n[%s]\n' "$1"
+}
+
+warn() {
+  warnings+=("$1")
+  printf 'WARNING: %s\n' "$1"
+}
+
+critical() {
+  criticals+=("$1")
+  status=1
+  printf 'CRITICAL: %s\n' "$1"
+}
+
+have() {
+  command -v "$1" >/dev/null 2>&1
+}
+
+run_if_available() {
+  local command_name="$1"
+  shift
+
+  if have "$command_name"; then
+    "$@" || warn "$command_name command failed"
+  else
+    warn "$command_name command not available"
+  fi
+}
+
+section "LOCAL NETWORK"
+if have ip; then
+  ip addr || warn "ip addr command failed"
+  printf '\nRouting table:\n'
+  ip route || warn "ip route command failed"
+  printf '\nDefault gateway:\n'
+  if ! ip route show default; then
+    critical "default gateway not found"
+  elif ! ip route show default | grep -q '^default '; then
+    critical "default gateway not configured"
+  fi
+else
+  warn "ip command not available"
+fi
+
+section "INTERFACES"
+active_interfaces=0
+if have ip; then
+  ip -br link || warn "interface state query failed"
+  active_interfaces="$(ip -br link 2>/dev/null | awk '$2 == "UP" && $1 != "lo" {count++} END {print count+0}')"
+  if (( active_interfaces == 0 )); then
+    critical "no active non-loopback interface detected"
+  else
+    printf 'OK: %s active non-loopback interface(s) detected\n' "$active_interfaces"
+  fi
+else
+  warn "cannot inspect interface state without ip command"
+fi
+
+section "DNS"
+if [[ -r /etc/resolv.conf ]]; then
+  cat /etc/resolv.conf
+else
+  warn "/etc/resolv.conf not readable"
+fi
+
+dns_target="${target:-localhost}"
+if have getent; then
+  if getent hosts "$dns_target" >/dev/null 2>&1; then
+    printf 'OK: DNS resolution succeeded for %s\n' "$dns_target"
+    getent hosts "$dns_target"
+  else
+    critical "DNS resolution failed for ${dns_target}"
+  fi
+elif have nslookup; then
+  if nslookup "$dns_target"; then
+    printf 'OK: DNS resolution succeeded for %s\n' "$dns_target"
+  else
+    critical "DNS resolution failed for ${dns_target}"
+  fi
+else
+  warn "no DNS lookup tool available"
+fi
+
+section "CONNECTIVITY"
+if [[ -n "$target" ]]; then
+  if have ping; then
+    if ping -c 3 -W 2 "$target"; then
+      printf 'OK: ping succeeded for %s\n' "$target"
+    else
+      critical "ping failed for ${target}"
+    fi
+  else
+    warn "ping command not available"
+  fi
+
+  run_if_available traceroute traceroute "$target"
+
+  if have nc; then
+    if nc -vz -w 3 "$target" 443; then
+      printf 'OK: TCP 443 reachable on %s\n' "$target"
+    else
+      critical "TCP 443 connectivity failed for ${target}"
+    fi
+  elif have curl; then
+    if curl --head --silent --show-error --connect-timeout 5 "https://${target}" >/dev/null; then
+      printf 'OK: HTTPS connectivity succeeded for %s\n' "$target"
+    else
+      critical "HTTPS connectivity failed for ${target}"
+    fi
+  else
+    warn "no TCP connectivity test tool available (nc or curl)"
+  fi
+else
+  printf 'OK: no target provided; skipped remote connectivity checks\n'
+fi
+
+section "PORTS"
+if have ss; then
+  ss -tuln || warn "ss command failed"
+else
+  warn "ss command not available"
+fi
+
+section "SUMMARY"
+if (( ${#criticals[@]} > 0 )); then
+  printf 'CRITICAL: %s issue(s) detected\n' "${#criticals[@]}"
+fi
+
+if (( ${#warnings[@]} > 0 )); then
+  printf 'WARNING: %s warning(s) detected\n' "${#warnings[@]}"
+fi
+
+if (( status == 0 )); then
+  printf 'OK: no obvious DNS or connectivity problems detected\n'
+fi
+
+exit "$status"