# Explorer frontend 404 fix — runbook

**Date:** 2026-03-02  
**Issue:** Root path (`/`) at https://explorer.d-bis.org returns 404 "Page not found".  
**Cause:** Nginx proxies `/` to Blockscout :4000; Blockscout is API-only and has no route for GET `/`.

**Status:** ✅ **FIXED** (2026-03-02). Nginx now serves the custom frontend from `/var/www/html` for `/` and SPA paths; `/api/v1/` and `/api/config/*` preserved. All endpoints verified 200.

---

## 1. How the UI is supposed to be served

This deployment uses a **custom frontend** (SolaceScanScout), not the built-in Blockscout web UI:

- **Static frontend:** Built files under `/var/www/html/` on VMID 5000:
  - `index.html` (main SPA shell, contains "SolaceScanScout")
  - `explorer-spa.js`, `favicon.ico`, `apple-touch-icon.png`, `/snap/`, etc.
- **Blockscout (port 4000):** API only. The Phoenix router has no route for `GET /`; it serves `/api/*` and returns 404 for `/`.
- **Nginx:** Should serve the static frontend for `/` and SPA paths, and proxy only `/api/`, `/api/v1/`, `/api/config/*`, `/health` to the appropriate backends (Blockscout :4000, token-aggregation :3001, or static config files).

**Relevant docs/config:**

- `explorer-monorepo/scripts/fix-nginx-serve-custom-frontend.sh` — nginx config that serves `/var/www/html` for `/` and SPA paths.
- `explorer-monorepo/scripts/fix-nginx-conflicts-vmid5000.sh` — current “conflicts” config: proxies `location /` to :4000 (no static root).
- `explorer-monorepo/scripts/deploy-frontend-to-vmid5000.sh` — deploys frontend files and can apply the custom-frontend nginx config.
- This runbook replaces ad-hoc 404 notes; use `explorer-monorepo/scripts/` above for nginx and deploy.
- `explorer-monorepo/docs/BLOCKSCOUT_START_AND_BUILD.md` — Blockscout container/assets; UI in this setup is the custom frontend, not Blockscout’s own UI.

---

## 2. What we confirmed on VMID 5000

- **Custom frontend present:** `/var/www/html/index.html` exists (~60KB), contains "SolaceScanScout"; `explorer-spa.js`, favicon, `/snap/`, etc. are present.
- **Blockscout logs:** For `GET /` to :4000, Blockscout logs:  
  `Phoenix.Router.NoRouteError`, "no route found for GET / (BlockScoutWeb.Router)". So 404 for `/` is expected when nginx sends `/` to Blockscout.
- **Live nginx:** HTTPS server block has `location / { proxy_pass http://127.0.0.1:4000; }` with **no** `root` / `try_files` for the frontend. So every request to `/` is proxied to Blockscout and returns 404.

Conclusion: the frontend files are in place; the **nginx config** is wrong (proxy-only for `/` instead of serving static files).

---

## 3. Fix: make nginx serve the custom frontend for `/`

Apply a config that, for the HTTPS (and optionally HTTP) server block:

1. Serves **`/`** from `/var/www/html` (e.g. `location = /` with `root /var/www/html` and `try_files /index.html =404`).
2. Serves **SPA paths** (e.g. `/address`, `/tx`, `/blocks`, …) from the same root with `try_files $uri $uri/ /index.html`.
3. Keeps **`/api/`**, **`/api/v1/`**, **`/api/config/*`**, **`/snap/`**, **`/health`** as they are (proxy or alias).

**Option A — Apply the full custom-frontend script (recommended)**

From the repo root, from a host that can SSH to the Proxmox node for VMID 5000 (e.g. r630-02):

```bash
# Set Proxmox host (r630-02)
export PROXMOX_R630_02=192.168.11.12   # or PROXMOX_HOST_R630_02

# Apply nginx config that serves / and SPA from /var/www/html
cd /home/intlc/projects/proxmox/explorer-monorepo
# Copy script into VM and run (requires pct exec)
EXPLORER_VM_HOST=root@192.168.11.12 bash scripts/apply-nginx-explorer-fix.sh
```

Or run the fix script **inside** VMID 5000 (e.g. after copying it in):

```bash
# From Proxmox host
pct exec 5000 -- bash /path/to/fix-nginx-serve-custom-frontend.sh
```

**Option B — Manual nginx change (HTTPS server block only)**

On VMID 5000, edit `/etc/nginx/sites-enabled/blockscout`. In the `server { listen 443 ... }` block, **replace** the single:

```nginx
location / {
    proxy_pass http://127.0.0.1:4000;
    ...
}
```

with something equivalent to:

```nginx
# Serve custom frontend for root
location = / {
    root /var/www/html;
    add_header Cache-Control "no-store, no-cache, must-revalidate";
    try_files /index.html =404;
}

# SPA paths — serve index.html for client-side routing
location ~ ^/(address|tx|block|token|tokens|blocks|transactions|bridge|weth|watchlist|nft|home|analytics|operator)(/|$) {
    root /var/www/html;
    try_files /index.html =404;
    add_header Cache-Control "no-store, no-cache, must-revalidate";
}

# All other non-API paths — static files and SPA fallback
location / {
    root /var/www/html;
    try_files $uri $uri/ /index.html;
}
```

Keep all existing `location /api/`, `location /api/v1/`, `location /api/config/`, `location /snap/`, `location /health` blocks unchanged and **before** the catch-all `location /` (so API and config still proxy correctly).

Then:

```bash
nginx -t && systemctl reload nginx
```

---

## 4. Verify

- From LAN:  
  `curl -sk -H "Host: explorer.d-bis.org" https://192.168.11.140:443/`  
  should return **200** with HTML containing "SolaceScanScout" (or similar), not "Page not found".
- Public:  
  `https://explorer.d-bis.org/` should show the explorer UI.
- API unchanged:  
  `curl -s http://192.168.11.140:4000/api/v2/stats` and `https://explorer.d-bis.org/api/v2/stats` should still return JSON.

---

## 5. Summary

| Item | Status |
|------|--------|
| How UI is served | Custom static frontend in `/var/www/html/` (index.html + SPA); Blockscout :4000 is API-only. |
| Frontend files on VMID 5000 | Present; `index.html` contains SolaceScanScout. |
| Blockscout logs for GET `/` | NoRouteError for GET `/` — expected when nginx proxies `/` to :4000. |
| Nginx fix | Serve `/` and SPA paths from `root /var/www/html` and `try_files`; proxy only `/api/` (and specific locations) to :4000. |
| Script to apply | `fix-nginx-serve-custom-frontend.sh` or `apply-nginx-explorer-fix.sh`; or apply the manual snippet above. |

---

## 6. Completion (2026-03-02)

- **Applied:** `apply-nginx-explorer-fix.sh` (via `EXPLORER_VM_HOST=root@192.168.11.12`).  
- **Script updated:** `fix-nginx-serve-custom-frontend.sh` now includes `location /api/v1/` (token-aggregation :3001) and `location = /api/config/token-list` / `location = /api/config/networks` (static JSON) so config and token-aggregation are not lost on re-apply.  
- **Verification:** From LAN, all return 200: `/` (frontend HTML), `/api/config/token-list`, `/api/config/networks`, `/api/v2/stats`, `/api/v1/chains`.