src/config.rs

@@ -612,6 +612,13 @@ pub fn load_config(path: &str) -> Result<ConfigLoad> {
             let filename = p.file_name().unwrap_or(p.as_os_str());
             v.push(crate::config_dir().join(filename));
             v.push(crate::data_dir().join(filename));
+            // Interactive root and sudo'd users: always consult the XDG path
+            // so `touch ~/.config/numa/numa.toml` works regardless of whether
+            // config_dir() routed to FHS (issue #81).
+            let suggested = crate::suggested_config_path();
+            if !v.contains(&suggested) {
+                v.push(suggested);
+            }
         }
         v
     };
@@ -632,11 +639,7 @@ pub fn load_config(path: &str) -> Result<ConfigLoad> {
         }
     }
 
-    // Show config_dir candidate as the "expected" path — it's actionable
+    let display_path = crate::suggested_config_path().to_string_lossy().to_string();
-    let display_path = candidates
-        .get(1)
-        .map(|p| p.to_string_lossy().to_string())
-        .unwrap_or_else(|| resolve_path(path));
     log::info!("config not found, using defaults (create {})", display_path);
     Ok(ConfigLoad {
         config: Config::default(),

src/lib.rs

@@ -44,6 +44,42 @@ pub fn hostname() -> String {
         .unwrap_or_else(|| "numa".to_string())
 }
 
+/// Path to suggest to an interactive user when asking them to create
+/// `numa.toml`. Prefers `$HOME/.config/numa/numa.toml` when HOME is set
+/// (actionable without sudo); falls back to `config_dir()` otherwise.
+///
+/// Note: `config_dir()` routes interactive root to FHS (`/var/lib/numa`)
+/// so that runtime state like `services.json` stays continuous with the
+/// installed daemon. This helper exists specifically to give advisories
+/// and `load_config` an XDG-aware path for user-authored config, without
+/// moving runtime state out of FHS — see issue #81.
+pub(crate) fn suggested_config_path() -> std::path::PathBuf {
+    #[cfg(not(windows))]
+    {
+        resolve_suggested_config_path(std::env::var("HOME").ok().as_deref(), config_dir)
+    }
+    #[cfg(windows)]
+    {
+        config_dir().join("numa.toml")
+    }
+}
+
+#[cfg(not(windows))]
+fn resolve_suggested_config_path<F>(home: Option<&str>, fallback_dir: F) -> std::path::PathBuf
+where
+    F: FnOnce() -> std::path::PathBuf,
+{
+    if let Some(home) = home {
+        if !home.is_empty() && home != "/" {
+            return std::path::PathBuf::from(home)
+                .join(".config")
+                .join("numa")
+                .join("numa.toml");
+        }
+    }
+    fallback_dir().join("numa.toml")
+}
+
 /// Shared config directory for persistent data (services.json, etc).
 /// Unix users: ~/.config/numa/
 /// Linux root daemon: /var/lib/numa (FHS) — falls back to /usr/local/var/numa
@@ -163,4 +199,73 @@ mod tests {
     fn linux_data_dir_only_fhs_uses_fhs() {
         assert_eq!(resolve_linux_data_dir(false, true), "/var/lib/numa");
     }
+
+    #[cfg(not(windows))]
+    fn fhs() -> std::path::PathBuf {
+        std::path::PathBuf::from("/var/lib/numa")
+    }
+
+    #[cfg(not(windows))]
+    #[test]
+    fn suggested_config_path_prefers_home() {
+        assert_eq!(
+            resolve_suggested_config_path(Some("/home/alice"), fhs),
+            std::path::PathBuf::from("/home/alice/.config/numa/numa.toml"),
+        );
+    }
+
+    #[cfg(not(windows))]
+    #[test]
+    fn suggested_config_path_prefers_root_home_over_fhs() {
+        // Interactive root: HOME=/root is a real user context, not a daemon signal.
+        // Advisory must point where load_config will actually look — issue #81.
+        assert_eq!(
+            resolve_suggested_config_path(Some("/root"), fhs),
+            std::path::PathBuf::from("/root/.config/numa/numa.toml"),
+        );
+    }
+
+    #[cfg(not(windows))]
+    #[test]
+    fn suggested_config_path_falls_back_when_home_unset() {
+        assert_eq!(
+            resolve_suggested_config_path(None, fhs),
+            std::path::PathBuf::from("/var/lib/numa/numa.toml"),
+        );
+    }
+
+    #[cfg(not(windows))]
+    #[test]
+    fn suggested_config_path_falls_back_when_home_is_root() {
+        // systemd services sometimes have HOME=/ — don't treat that as a real home.
+        assert_eq!(
+            resolve_suggested_config_path(Some("/"), fhs),
+            std::path::PathBuf::from("/var/lib/numa/numa.toml"),
+        );
+    }
+
+    #[cfg(not(windows))]
+    #[test]
+    fn suggested_config_path_falls_back_when_home_is_empty() {
+        assert_eq!(
+            resolve_suggested_config_path(Some(""), fhs),
+            std::path::PathBuf::from("/var/lib/numa/numa.toml"),
+        );
+    }
+
+    #[cfg(not(windows))]
+    #[test]
+    fn suggested_config_path_skips_fallback_when_home_valid() {
+        // Happy path shouldn't probe the filesystem via config_dir().
+        let called = std::cell::Cell::new(false);
+        let fallback = || {
+            called.set(true);
+            std::path::PathBuf::from("/should/not/be/used")
+        };
+        let _ = resolve_suggested_config_path(Some("/home/alice"), fallback);
+        assert!(
+            !called.get(),
+            "fallback must not be invoked when HOME is valid"
+        );
+    }
 }

src/system_dns.rs

@@ -91,7 +91,7 @@ pub fn try_port53_advisory(bind_addr: &str, err: &std::io::Error) -> Option<Stri
          sudo numa install       (on Windows, run as Administrator)
 
     2. Run on a non-privileged port for testing.
-       Create ~/.config/numa/numa.toml with:
+       Create {} with:
 
          [server]
          bind_addr = \"127.0.0.1:5354\"
@@ -100,7 +100,8 @@ pub fn try_port53_advisory(bind_addr: &str, err: &std::io::Error) -> Option<Stri
        Then run:  numa
        Test with: dig @127.0.0.1 -p 5354 example.com
 
-"
+",
+        crate::suggested_config_path().display()
     ))
 }
 

src/tls.rs

@@ -66,13 +66,14 @@ pub fn try_data_dir_advisory(err: &crate::Error, data_dir: &Path) -> Option<Stri
          sudo numa install       (on Windows, run as Administrator)
 
     2. Point data_dir at a path you can write.
-       Create ~/.config/numa/numa.toml with:
+       Create {} with:
 
          [server]
          data_dir = \"/path/you/can/write\"
 
 ",
-        data_dir.display()
+        data_dir.display(),
+        crate::suggested_config_path().display()
     ))
 }
 

tests/docker/hold53.py

@@ -0,0 +1,5 @@
+import socket, signal
+s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 0)
+s.bind(("", 53))
+signal.pause()

tests/docker/issue-81.sh

@@ -0,0 +1,164 @@
+#!/usr/bin/env bash
+#
+# End-to-end validation of the issue #81 fix (config path advisory).
+#
+# Builds numa from two source trees — the buggy baseline and the fix
+# candidate — inside one debian:bookworm container, then runs four
+# scenarios to prove:
+#
+#   1. replication/main  — reporter's sequence, bug confirmed
+#   2. replication/fix   — reporter's sequence, bug is gone
+#   3. existing/main     — pre-installed config at FHS data dir still loads
+#   4. existing/fix      — same, unchanged by the fix (no regression)
+#
+# Scenarios 3 and 4 guard against the fear that the fix might change
+# candidate order and break existing daemon installs (including the
+# macOS Homebrew-prefix layout at /usr/local/var/numa/).
+#
+# Usage:
+#   MAIN_SRC=/path/to/main-checkout FIX_SRC=/path/to/fix-worktree \
+#     ./tests/docker/issue-81.sh
+#
+# Defaults: MAIN_SRC = $(git rev-parse --show-toplevel), FIX_SRC = same.
+
+set -euo pipefail
+
+MAIN_SRC="${MAIN_SRC:-$(git rev-parse --show-toplevel)}"
+FIX_SRC="${FIX_SRC:-$MAIN_SRC}"
+
+GREEN="\033[32m"; RED="\033[31m"; RESET="\033[0m"
+
+echo "── issue #81 validation ──"
+echo "  main: $MAIN_SRC"
+echo "  fix:  $FIX_SRC"
+echo
+
+docker run --rm \
+    --platform linux/amd64 \
+    -v "$MAIN_SRC:/main:ro" \
+    -v "$FIX_SRC:/fix:ro" \
+    -v "$(dirname "$0")/hold53.py:/tmp/hold53.py:ro" \
+    -v numa-port53-cargo:/root/.cargo \
+    -v numa-port53-target:/work/target \
+    debian:bookworm bash -c '
+set -euo pipefail
+
+# Paths and ports used by all scenarios — keep in one place so the
+# heredocs and the verdict greps cannot drift.
+XDG_CONFIG="/root/.config/numa/numa.toml"
+FHS_CONFIG="/var/lib/numa/numa.toml"
+TEST_PORT="5354"
+TEST_API_PORT="5380"
+
+apt-get update -qq && apt-get install -y -qq curl build-essential python3 2>&1 | tail -1
+if ! command -v cargo &>/dev/null; then
+    curl -sSf https://sh.rustup.rs | sh -s -- -y --profile minimal --quiet
+fi
+. "$HOME/.cargo/env"
+
+build_from() {
+    local label="$1"; local src="$2"
+    mkdir -p "/work/$label"
+    tar -C "$src" --exclude=./target --exclude=./.git -cf - . | tar -C "/work/$label" -xf -
+    (cd "/work/$label" && cargo build --release --locked 2>&1 | tail -1)
+    cp "/work/$label/target/release/numa" "/work/numa-$label"
+}
+
+build_from main /main
+build_from fix /fix
+
+holder=0
+stop_holder() {
+    if [ "$holder" -ne 0 ]; then
+        kill "$holder" 2>/dev/null || true
+        wait "$holder" 2>/dev/null || true
+        holder=0
+    fi
+}
+trap stop_holder EXIT
+
+start_holder() {
+    python3 /tmp/hold53.py &
+    holder=$!
+    sleep 0.3
+}
+
+write_test_config() {
+    local path="$1"
+    mkdir -p "$(dirname "$path")"
+    cat > "$path" <<EOF
+[server]
+bind_addr = "127.0.0.1:$TEST_PORT"
+api_port = $TEST_API_PORT
+EOF
+}
+
+verdict() {
+    local label="$1"; local expected="$2"; local file="$3"
+    # "cannot bind to" is printed by the advisory when numa fails to start.
+    # Its absence is a reliable proxy for "numa bound successfully" because
+    # the banner-only log we capture contains no other failure surface.
+    if grep -q "cannot bind to" "$file"; then
+        echo "  [$label] did not bind $TEST_PORT — numa ignored the XDG config"
+        [ "$expected" = "ignored" ] && return 0 || return 1
+    else
+        echo "  [$label] bound $TEST_PORT — config loaded"
+        [ "$expected" = "bound" ] && return 0 || return 1
+    fi
+}
+
+scenario_replication() {
+    local label="$1"; local bin="/work/numa-$label"; local expected="$2"
+    echo
+    echo "════════ REPLICATION / $label ════════"
+    rm -rf /root/.config/numa /var/lib/numa
+    mkdir -p "$(dirname "$XDG_CONFIG")"
+
+    start_holder
+    set +e
+    timeout 5 "$bin" > /tmp/run1.txt 2>&1
+    set -e
+    echo "── step 1: advisory printed by $label ──"
+    grep -E "Create .* with:" /tmp/run1.txt | sed "s/^/  /" || echo "  <no advisory line>"
+
+    write_test_config "$XDG_CONFIG"
+    echo "── step 2: wrote config at $XDG_CONFIG ──"
+
+    set +e
+    timeout 3 "$bin" > /tmp/run2.txt 2>&1
+    set -e
+    stop_holder
+
+    verdict "$label" "$expected" /tmp/run2.txt
+}
+
+scenario_existing_install() {
+    local label="$1"; local bin="/work/numa-$label"
+    echo
+    echo "════════ EXISTING INSTALL / $label ════════"
+    rm -rf /root/.config/numa /var/lib/numa
+    write_test_config "$FHS_CONFIG"
+
+    start_holder
+    set +e
+    timeout 3 "$bin" > /tmp/run.txt 2>&1
+    set -e
+    stop_holder
+
+    verdict "$label" "bound" /tmp/run.txt
+}
+
+RC=0
+scenario_replication main ignored || RC=1
+scenario_replication fix bound || RC=1
+scenario_existing_install main || RC=1
+scenario_existing_install fix || RC=1
+
+echo
+if [ "$RC" -eq 0 ]; then
+    echo "── all scenarios matched expectations ──"
+else
+    echo "── FAILURE: one or more scenarios diverged ──"
+fi
+exit $RC
+'