diff --git a/README.md b/README.md
index 49c0dd4..1b88c6d 100644
--- a/README.md
+++ b/README.md
@@ -91,6 +91,21 @@ deno task test    # unit tests (sync, reconciliation, rules, reports)
 deno task check   # svelte-check
 ```
 
+### Troubleshooting: "unable to open database file"
+
+The container runs as the non-root `deno` user (uid 1000), so `/data` must be
+writable by it:
+
+- **Named volume** (`-v quantum-data:/data`) — works out of the box; Podman and
+  Docker copy the image's ownership into a fresh volume.
+- **Bind mount** (`-v /srv/quantum:/data`) — the host directory keeps its host
+  ownership. With rootless Podman, either add the `:U` option
+  (`-v /srv/quantum:/data:U`, chowns to the container user) or run
+  `podman unshare chown -R 1000:1000 /srv/quantum` once. On SELinux hosts
+  (Fedora and friends) you also want `:Z`, i.e. `:U,Z`.
+- A volume first created by some other image/user keeps its old ownership;
+  `podman volume inspect` shows its path if you need to fix it up.
+
 ## Operational notes
 
 - **The database file is secret-grade.** It contains the SimpleFIN Access URL
diff --git a/src/lib/server/db.ts b/src/lib/server/db.ts
index 7417ea5..d0d546b 100644
--- a/src/lib/server/db.ts
+++ b/src/lib/server/db.ts
@@ -1,6 +1,7 @@
 import { DatabaseSync } from 'node:sqlite';
 import { mkdirSync, readFileSync, readdirSync } from 'node:fs';
 import { dirname, join } from 'node:path';
+import process from 'node:process';
 
 const MIGRATION_FILE = /^(\d+)_.*\.sql$/;
 
@@ -18,8 +19,21 @@ export function getDb(): DatabaseSync {
 }
 
 export function openDatabase(dbPath: string, migrationsDir: string): DatabaseSync {
-	if (dbPath !== ':memory:') mkdirSync(dirname(dbPath), { recursive: true });
-	const db = new DatabaseSync(dbPath);
+	let db: DatabaseSync;
+	try {
+		if (dbPath !== ':memory:') mkdirSync(dirname(dbPath), { recursive: true });
+		db = new DatabaseSync(dbPath);
+	} catch (err) {
+		const reason = err instanceof Error ? err.message : String(err);
+		throw new Error(
+			`Cannot open database at ${dbPath}: ${reason}\n` +
+				`The server runs as uid ${process.getuid?.() ?? '?'} — the directory must be ` +
+				`writable by it. In a container, bind mounts keep host ownership: with rootless ` +
+				`Podman use "-v /host/path:/data:U" (chowns to the container user) or ` +
+				`"podman unshare chown -R 1000:1000 /host/path"; a named volume ` +
+				`(-v quantum-data:/data) inherits correct ownership from the image automatically.`
+		);
+	}
 	db.exec('PRAGMA journal_mode = WAL');
 	db.exec('PRAGMA foreign_keys = ON');
 	runMigrations(db, migrationsDir);