fix(installer): safer disk picker, single install at a time, surface silent archinstall failures

- drives: classify by lsblk TRAN/ROTA (SATA SSDs were labelled HDD and lost
  to bigger spinning disks); drop zram, eMMC boot/rpmb areas, read-only and
  0-byte disks; grey out disks under 16 GB; rank USB disks last; warn about
  >2 TB disks on BIOS (MBR); boot-stick fallback via archiso kernel args
  when bootmnt is gone; timeouts on lsblk/smartctl/blkid
- step 2 only accepts a disk that was actually offered
- /install/run refuses a second concurrent install and disables the button
- archinstall's exit code is tracked: OOM kills / signals now show as errors
  instead of a progress bar stuck forever
- disk-probe exceptions land in the install log instead of a bare 500

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_app.py

@@ -226,3 +226,108 @@ def test_log_page_running_state_has_no_restart_button(monkeypatch, tmp_path):
     html = app_module.app.test_client().get("/install/log").get_data(as_text=True)
     assert "next-steps" not in html
     assert "install_reboot" not in html and "restart now" not in html
+
+
+def test_nonzero_exit_without_traceback_is_an_error():
+    import app as app_module
+
+    # OOM kill / signal: archinstall dies mid-pacstrap and prints nothing.
+    log = "Installing packages: ['base'\n"
+    assert app_module.parse_install_progress(log)["status"] == "running"
+    assert app_module.parse_install_progress(log, exit_code=-9)["status"] == "error"
+    assert app_module.parse_install_progress(log, exit_code=0)["status"] == "running"
+
+
+class _FakeProc:
+    def __init__(self, code=None):
+        self.code = code
+
+    def poll(self):
+        return self.code
+
+
+def _install_env(monkeypatch, tmp_path):
+    import app as app_module
+
+    monkeypatch.setattr(app_module, "STATE_DIR", tmp_path)
+    monkeypatch.setattr(app_module, "INSTALL_LOG", tmp_path / "install.log")
+    monkeypatch.setattr(app_module, "_install_proc", None)
+    monkeypatch.delenv("FURTKA_DRY_RUN", raising=False)
+    monkeypatch.setitem(app_module.settings, "boot_drive", "/dev/sda")
+    monkeypatch.setitem(app_module.settings, "username", "u")
+    monkeypatch.setitem(app_module.settings, "password", "pw12345678")
+    monkeypatch.setattr(app_module, "release_disk", lambda d: [f"released {d}"])
+    monkeypatch.setattr(app_module, "build_disk_config", lambda d: {"device": d})
+    return app_module
+
+
+def test_install_run_refuses_second_concurrent_install(monkeypatch, tmp_path):
+    app_module = _install_env(monkeypatch, tmp_path)
+    spawned = []
+    monkeypatch.setattr(
+        app_module, "spawn_archinstall", lambda *a: spawned.append(a) or _FakeProc()
+    )
+    client = app_module.app.test_client()
+    assert client.post("/install/run").status_code == 302
+    assert client.post("/install/run").status_code == 302
+    assert len(spawned) == 1
+
+
+def test_install_run_disk_probe_failure_lands_in_log(monkeypatch, tmp_path):
+    app_module = _install_env(monkeypatch, tmp_path)
+
+    def boom(_):
+        raise RuntimeError("parted could not read /dev/sda")
+
+    monkeypatch.setattr(app_module, "build_disk_config", boom)
+    resp = app_module.app.test_client().post("/install/run")
+    assert resp.status_code == 302
+    log = (tmp_path / "install.log").read_text()
+    assert "Traceback (most recent call last)" in log
+    assert app_module.parse_install_progress(log)["status"] == "error"
+
+
+def test_install_log_json_reports_crashed_archinstall(monkeypatch, tmp_path):
+    app_module = _install_env(monkeypatch, tmp_path)
+    (tmp_path / "install.log").write_text("Installing packages: ['base'\n")
+    monkeypatch.setattr(app_module, "_install_proc", _FakeProc(code=137))
+    data = app_module.app.test_client().get("/install/log.json").get_json()
+    assert data["progress"]["status"] == "error"
+    assert "exit code 137" in data["log"]
+
+
+def test_step2_rejects_disk_not_offered(monkeypatch):
+    import app as app_module
+
+    offered = [
+        {
+            "name": "/dev/sda",
+            "usable": True,
+            "size": "500 GB",
+            "type_label": "SSD",
+            "health_label": "Healthy",
+            "score": 27,
+            "reason": "",
+            "warning": "",
+        },
+        {
+            "name": "/dev/sdb",
+            "usable": False,
+            "size": "8 GB",
+            "type_label": "USB",
+            "health_label": "Status unknown",
+            "score": 10,
+            "reason": "Too small",
+            "warning": "",
+        },
+    ]
+    monkeypatch.setattr(app_module, "list_scored_devices", lambda: offered)
+    monkeypatch.setitem(app_module.settings, "boot_drive", "")
+    client = app_module.app.test_client()
+    for bad in ("/dev/sdb", "/dev/nope", "/etc/passwd"):
+        resp = client.post("/install/step2", data={"boot_drive": bad})
+        assert resp.status_code == 200
+        assert app_module.settings["boot_drive"] == ""
+    resp = client.post("/install/step2", data={"boot_drive": "/dev/sda"})
+    assert resp.status_code == 302
+    assert app_module.settings["boot_drive"] == "/dev/sda"

tests/test_drives.py

@@ -1,47 +1,63 @@
+import json
+
+import drives
+import pytest
 from drives import (
-    get_drive_type_label,
+    MIN_DISK_GB,
+    _boot_device_from_cmdline,
+    classify_drive,
+    format_size,
     get_drive_type_score,
     get_size_score,
-    parse_lsblk_output,
+    parse_lsblk_json,
-    parse_size_gb,
-    score_device,
 )
 
-
+GB = 1024**3
-def test_parse_size_gb_terabytes():
-    assert parse_size_gb("1T") == 1024.0
 
 
-def test_parse_size_gb_gigabytes():
+def _lsblk(*entries):
-    assert parse_size_gb("500G") == 500.0
+    """Build lsblk -J output. Each entry: (name, size_gb, type, extra-dict)."""
+    devs = []
+    for name, size_gb, dev_type, *extra in entries:
+        d = {
+            "name": name,
+            "size": int(size_gb * GB),
+            "type": dev_type,
+            "ro": False,
+            "rm": False,
+            "tran": "sata",
+            "rota": True,
+        }
+        if extra:
+            d.update(extra[0])
+        devs.append(d)
+    return json.dumps({"blockdevices": devs})
 
 
-def test_parse_size_gb_megabytes():
+@pytest.fixture(autouse=True)
-    assert parse_size_gb("2048M") == 2.0
+def _smart_passed(monkeypatch):
+    monkeypatch.setattr(drives, "_smart_status", lambda _: "passed")
 
 
-def test_parse_size_gb_european_comma_decimal():
+def _names(devices):
-    assert parse_size_gb("1,5T") == 1.5 * 1024
+    return [d["name"] for d in devices]
 
 
-def test_parse_size_gb_empty_returns_none():
+def test_classify_uses_transport_and_rotation():
-    assert parse_size_gb("") is None
+    assert classify_drive("nvme0n1", tran="nvme", rota=False) == "NVMe"
+    assert classify_drive("sda", tran="sata", rota=False) == "SSD"
+    assert classify_drive("sda", tran="sata", rota=True) == "HDD"
+    assert classify_drive("mmcblk0", tran="", rota=False) == "eMMC"
+    assert classify_drive("sdb", tran="usb", rota=False) == "USB"
+    assert classify_drive("sdc", tran="", rota=True, removable=True) == "USB"
+    # SD cards in a built-in reader are removable mmc — still eMMC/mmc class.
+    assert classify_drive("mmcblk1", tran="", rota=False, removable=True) == "eMMC"
 
 
-def test_parse_size_gb_unknown_unit_returns_none():
+def test_type_scores_rank_internal_over_usb():
-    assert parse_size_gb("500K") is None
+    assert get_drive_type_score("NVMe") > get_drive_type_score("SSD")
-
+    assert get_drive_type_score("SSD") > get_drive_type_score("HDD")
-
+    assert get_drive_type_score("HDD") > get_drive_type_score("USB")
-def test_drive_type_score_nvme():
-    assert get_drive_type_score("/dev/nvme0n1") == 15
-
-
-def test_drive_type_score_ssd():
-    assert get_drive_type_score("/dev/ssd0") == 10
-
-
-def test_drive_type_score_hdd_fallback():
-    assert get_drive_type_score("/dev/sda") == 5
 
 
 def test_size_score_bands():
@@ -51,67 +67,145 @@ def test_size_score_bands():
     assert get_size_score(1024) == 10
 
 
-def test_score_device_sums_type_and_size(monkeypatch):
+def test_format_size():
-    import drives
+    assert format_size(500 * GB) == "500 GB"
-
+    assert format_size(1024 * GB) == "1 TB"
-    monkeypatch.setattr(drives, "get_drive_health", lambda _: 10)
+    assert format_size(int(1.5 * 1024 * GB)) == "1.5 TB"
-    assert score_device("/dev/nvme0n1", 1024) == 15 + 10 + 10
+    assert format_size(int(7.5 * GB)) == "7.5 GB"
-    assert score_device("/dev/sda", 64) == 5 + 10 + 5
 
 
-def test_parse_lsblk_drops_loop_and_rom(monkeypatch):
+def test_drops_loop_rom_zram_and_emmc_boot_areas():
-    import drives
+    out = _lsblk(
-
+        ("loop0", 2.5, "loop"),
-    monkeypatch.setattr(drives, "_smart_status", lambda _: "passed")
+        ("sr0", 1, "rom"),
-    output = "loop0   2.5G loop\nsr0    1024M rom\nsda    500G disk\nnvme0n1  1T disk\n"
+        ("zram0", 4, "disk"),
-    devices = parse_lsblk_output(output)
+        ("mmcblk0boot0", 0.004, "disk"),
-    names = [d["name"] for d in devices]
+        ("mmcblk0boot1", 0.004, "disk"),
-    assert names == ["/dev/nvme0n1", "/dev/sda"]
+        ("mmcblk0rpmb", 0.004, "disk"),
+        ("mmcblk0", 64, "disk", {"tran": "", "rota": False}),
+    )
+    assert _names(parse_lsblk_json(out)) == ["/dev/mmcblk0"]
 
 
-def test_parse_lsblk_attaches_human_labels(monkeypatch):
+def test_drops_empty_card_reader_slots_and_read_only_disks():
-    import drives
+    out = _lsblk(
-
+        ("sdc", 0, "disk", {"rm": True, "tran": "usb"}),
-    monkeypatch.setattr(drives, "_smart_status", lambda _: "passed")
+        ("sdd", 500, "disk", {"ro": True}),
-    output = "nvme0n1  1T disk\n"
+        ("sda", 500, "disk"),
-    [dev] = parse_lsblk_output(output)
+    )
-    assert dev["type_label"] == "NVMe"
+    assert _names(parse_lsblk_json(out)) == ["/dev/sda"]
-    assert dev["health_label"] == "Healthy"
 
 
-def test_parse_lsblk_surfaces_smart_warning(monkeypatch):
+def test_ssd_beats_bigger_hdd():
-    import drives
+    # Regression: sdX SSDs used to be labelled HDD, so the 2 TB spinning disk
+    # won the recommendation over the 256 GB SSD.
+    out = _lsblk(
+        ("sda", 2048, "disk", {"rota": True}),
+        ("sdb", 256, "disk", {"rota": False}),
+    )
+    devices = parse_lsblk_json(out)
+    assert _names(devices) == ["/dev/sdb", "/dev/sda"]
+    assert [d["type_label"] for d in devices] == ["SSD", "HDD"]
 
+
+def test_usb_disk_ranked_after_internal():
+    out = _lsblk(
+        ("sda", 32, "disk", {"tran": "usb", "rota": False, "rm": True}),
+        ("mmcblk0", 32, "disk", {"tran": "", "rota": False}),
+    )
+    devices = parse_lsblk_json(out)
+    assert _names(devices) == ["/dev/mmcblk0", "/dev/sda"]
+    assert devices[1]["warning"]
+
+
+def test_too_small_disk_listed_but_unusable_and_last():
+    out = _lsblk(
+        ("sda", MIN_DISK_GB - 1, "disk", {"rota": False}),
+        ("sdb", 500, "disk"),
+    )
+    devices = parse_lsblk_json(out)
+    assert _names(devices) == ["/dev/sdb", "/dev/sda"]
+    assert devices[0]["usable"] is True
+    assert devices[1]["usable"] is False
+    assert str(MIN_DISK_GB) in devices[1]["reason"]
+
+
+def test_bios_warns_about_disks_over_2tb():
+    out = _lsblk(("sda", 4096, "disk"))
+    [bios] = parse_lsblk_json(out, uefi=False)
+    [efi] = parse_lsblk_json(out, uefi=True)
+    assert "2 TB" in bios["warning"]
+    assert efi["warning"] == ""
+
+
+def test_surfaces_smart_warning(monkeypatch):
     monkeypatch.setattr(drives, "_smart_status", lambda _: "failed")
-    [dev] = parse_lsblk_output("sda 500G disk\n")
+    [dev] = parse_lsblk_json(_lsblk(("sda", 500, "disk")))
     assert dev["health_label"] == "SMART warning"
 
 
-def test_drive_type_label_nvme_ssd_hdd():
+def test_accepts_old_util_linux_string_flags():
-    assert get_drive_type_label("/dev/nvme0n1") == "NVMe"
+    out = json.dumps(
-    assert get_drive_type_label("/dev/ssd0") == "SSD"
+        {
-    assert get_drive_type_label("/dev/sda") == "HDD"
+            "blockdevices": [
+                {
+                    "name": "sda",
+                    "size": str(500 * GB),
+                    "type": "disk",
+                    "ro": "0",
+                    "rm": "0",
+                    "tran": "sata",
+                    "rota": "0",
+                },
+            ]
+        }
+    )
+    [dev] = parse_lsblk_json(out)
+    assert dev["type_label"] == "SSD"
 
 
-def test_parse_lsblk_handles_empty_output():
+def test_handles_empty_and_garbage_output():
-    assert parse_lsblk_output("") == []
+    assert parse_lsblk_json("") == []
+    assert parse_lsblk_json("not json") == []
 
 
-def test_parse_lsblk_drops_boot_usb(monkeypatch):
+def test_drops_boot_usb():
-    import drives
+    out = _lsblk(
-
+        ("sda", 500, "disk"),
-    monkeypatch.setattr(drives, "_smart_status", lambda _: "passed")
+        ("sdb", 16, "disk", {"tran": "usb"}),
-    output = "sda    500G disk\nsdb     16G disk\nnvme0n1  1T disk\n"
+        ("nvme0n1", 1024, "disk", {"tran": "nvme", "rota": False}),
-    devices = parse_lsblk_output(output, boot_disk="sdb")
+    )
-    names = [d["name"] for d in devices]
+    assert _names(parse_lsblk_json(out, boot_disk="sdb")) == ["/dev/nvme0n1", "/dev/sda"]
-    assert "/dev/sdb" not in names
-    assert names == ["/dev/nvme0n1", "/dev/sda"]
 
 
-def test_parse_lsblk_no_boot_disk_keeps_all(monkeypatch):
+def test_boot_device_from_cmdline(monkeypatch):
-    import drives
+    calls = []
 
-    monkeypatch.setattr(drives, "_smart_status", lambda _: "passed")
+    class R:
-    output = "sda 500G disk\nsdb  16G disk\n"
+        returncode = 0
-    names = [d["name"] for d in parse_lsblk_output(output, boot_disk=None)]
+        stdout = "/dev/sdb1\n"
-    assert set(names) == {"/dev/sda", "/dev/sdb"}
+
+    monkeypatch.setattr(drives, "_run", lambda cmd, **_: calls.append(cmd) or R())
+    cmdline = "BOOT_IMAGE=/vmlinuz archisosearchuuid=2026-08-25-10-00-00-00 quiet"
+    assert _boot_device_from_cmdline(cmdline) == "/dev/sdb1"
+    assert calls[-1] == ["blkid", "-U", "2026-08-25-10-00-00-00"]
+    assert _boot_device_from_cmdline("archisolabel=FURTKA_2620") == "/dev/sdb1"
+    assert calls[-1] == ["blkid", "-L", "FURTKA_2620"]
+    assert _boot_device_from_cmdline("archisodevice=/dev/sr0") == "/dev/sr0"
+    assert _boot_device_from_cmdline("quiet splash") is None
+
+
+def test_boot_disk_whole_disk_iso(monkeypatch):
+    # dd-written stick: ISO filesystem on the whole disk, PKNAME empty.
+    class R:
+        def __init__(self, out):
+            self.returncode = 0
+            self.stdout = out
+
+    def fake_run(cmd, **_):
+        if cmd[0] == "findmnt":
+            return R("/dev/sdb\n")
+        return R("\n")
+
+    monkeypatch.setattr(drives, "_run", fake_run)
+    assert drives._boot_disk_name() == "sdb"

webinstaller/app.py

@@ -8,6 +8,8 @@ import os
 import re
 import subprocess
 import sys
+import threading
+import traceback
 from datetime import UTC
 from pathlib import Path
 
@@ -108,7 +110,13 @@ PROGRESS_ERROR_HINTS = [
 ]
 
 
-def parse_install_progress(log):
+def parse_install_progress(log, exit_code=None):
+    """Progress dict from the install log.
+
+    `exit_code` is archinstall's return code once the process has ended
+    (None while running or unknown). A non-zero exit is an error even when
+    the log has no Traceback — OOM kills and signals print nothing.
+    """
     percent = 2
     phase = "Starting up…"
     for marker, pct, label in PROGRESS_PHASES:
@@ -118,7 +126,7 @@ def parse_install_progress(log):
 
     if percent >= 100:
         status = "done"
-    elif any(m in log for m in PROGRESS_ERROR_MARKERS):
+    elif any(m in log for m in PROGRESS_ERROR_MARKERS) or exit_code not in (None, 0):
         status = "error"
         phase = "Installation failed — open Show details below"
         for marker, hint in PROGRESS_ERROR_HINTS:
@@ -127,6 +135,13 @@ def parse_install_progress(log):
                 break
     else:
         status = "running"
+        if percent == 18:
+            # archinstall waits for NTP time sync with no timeout. Only a hint:
+            # it usually clears on its own within a minute.
+            phase = (
+                "Syncing time and packages — if this takes more than a few "
+                "minutes, check that the network cable is plugged in"
+            )
 
     return {"percent": percent, "phase": phase, "status": status}
 
@@ -596,15 +611,20 @@ def install_step_1():
 
 @app.route("/install/step2", methods=["GET", "POST"])
 def install_step_2():
+    drives = list_scored_devices()
+    error = ""
     if request.method == "POST":
         boot_drive = request.form.get("boot_drive", "").strip()
-        if boot_drive:
+        # Only accept a disk we actually offered — never a free-form path.
+        if any(d["name"] == boot_drive and d["usable"] for d in drives):
             settings["boot_drive"] = boot_drive
             return redirect(url_for("install_overview"))
+        error = "Please pick one of the disks below."
     return render_template(
         "install/step2.html",
-        drives=list_scored_devices(),
+        drives=drives,
         selected=settings.get("boot_drive", ""),
+        error=error,
     )
 
 
@@ -614,12 +634,50 @@ def install_overview():
     return render_template("install/overview.html", settings=masked)
 
 
+# The running archinstall process, so a second click (double-submit, Back +
+# Install again, a second browser) can't start another install on the same
+# disk, and so the progress page can see an exit without a Traceback.
+_install_proc = None
+_install_lock = threading.Lock()
+
+
+def _install_exit_code():
+    return None if _install_proc is None else _install_proc.poll()
+
+
+def _read_install_log():
+    log = INSTALL_LOG.read_text(errors="replace") if INSTALL_LOG.exists() else ""
+    code = _install_exit_code()
+    if code not in (None, 0):
+        log += f"\n\narchinstall stopped unexpectedly (exit code {code}).\n"
+    return log, code
+
+
 @app.route("/install/run", methods=["POST"])
 def install_run():
     if not settings["boot_drive"] or not settings["username"] or not settings["password"]:
         return redirect(url_for("install_step_1"))
-    config_path, creds_path = write_install_files(settings, STATE_DIR)
+    with _install_lock:
+        if _install_proc is not None and _install_proc.poll() is None:
+            return redirect(url_for("install_log_view"))
+        return _start_install()
+
+
+def _start_install():
+    global _install_proc
+    STATE_DIR.mkdir(parents=True, exist_ok=True)
     INSTALL_LOG.write_bytes(b"")
+    try:
+        config_path, creds_path = write_install_files(settings, STATE_DIR)
+    except Exception:
+        # archinstall's disk probe raises on disks it can't parse (broken
+        # GPT, odd card readers). Put the traceback where the progress page
+        # finds it instead of a bare "Internal Server Error".
+        with INSTALL_LOG.open("a") as fh:
+            fh.write(
+                f"Could not read the layout of {settings['boot_drive']}.\n" + traceback.format_exc()
+            )
+        return redirect(url_for("install_log_view"))
     if os.environ.get("FURTKA_DRY_RUN") == "1":
         INSTALL_LOG.write_text(
             f"DRY RUN: would exec archinstall --config {config_path} "
@@ -631,33 +689,33 @@ def install_run():
         # while those hold the partitions open (first hardware bench, 26.19).
         with INSTALL_LOG.open("a") as fh:
             fh.write("\n".join(release_disk(settings["boot_drive"])) + "\n\n")
-        spawn_archinstall(config_path, creds_path, INSTALL_LOG)
+        _install_proc = spawn_archinstall(config_path, creds_path, INSTALL_LOG)
     return redirect(url_for("install_log_view"))
 
 
 @app.route("/install/log")
 def install_log_view():
-    log = INSTALL_LOG.read_text() if INSTALL_LOG.exists() else ""
+    log, code = _read_install_log()
     return render_template(
         "install/log.html",
         log=log,
-        progress=parse_install_progress(log),
+        progress=parse_install_progress(log, code),
         hostname=settings["hostname"],
     )
 
 
 @app.route("/install/log.json")
 def install_log_json():
-    log = INSTALL_LOG.read_text() if INSTALL_LOG.exists() else ""
+    log, code = _read_install_log()
-    return jsonify(log=log, progress=parse_install_progress(log))
+    return jsonify(log=log, progress=parse_install_progress(log, code))
 
 
 @app.route("/install/reboot", methods=["POST"])
 def install_reboot():
     # Only allow rebooting once the install has actually finished — we don't
     # want a panicked click during install to reboot mid-pacstrap.
-    log = INSTALL_LOG.read_text() if INSTALL_LOG.exists() else ""
+    log, code = _read_install_log()
-    if parse_install_progress(log)["status"] != "done":
+    if parse_install_progress(log, code)["status"] != "done":
         return redirect(url_for("install_log_view"))
     # Delay reboot a few seconds so the browser can finish fetching CSS / assets
     # for the rebooting page before the Flask server (and network) go away.

webinstaller/drives.py

@@ -1,55 +1,89 @@
+import json
+import re
 import subprocess
+from pathlib import Path
+
+# Smallest disk we offer as an install target. The base system plus Docker
+# needs ~6 GB; the rest is headroom for images and app data.
+MIN_DISK_GB = 16
+
+# MBR (what archinstall lays out on BIOS boxes) can't address past 2 TiB.
+MBR_LIMIT_GB = 2048
+
+# Block devices lsblk reports as TYPE=disk that are never install targets:
+# compressed RAM swap and the eMMC hardware boot / RPMB areas (4 MB, usually
+# read-only) that show up next to mmcblk0 on every eMMC mini-PC and laptop.
+_PSEUDO_DISK_RE = re.compile(r"^(zram\d+|mmcblk\d+boot\d+|mmcblk\d+rpmb)$")
+
+_SUBPROCESS_TIMEOUT = 15
+
+
+def _run(cmd, timeout=_SUBPROCESS_TIMEOUT):
+    """subprocess.run with a timeout; None when the tool is missing or hangs."""
+    try:
+        return subprocess.run(cmd, capture_output=True, text=True, timeout=timeout)
+    except (FileNotFoundError, subprocess.TimeoutExpired):
+        return None
+
+
+def _parent_disk(device):
+    result = _run(["lsblk", "-no", "PKNAME", device])
+    if result is None or result.returncode != 0:
+        return None
+    lines = [line.strip() for line in result.stdout.splitlines() if line.strip()]
+    return lines[0] if lines else None
+
+
+def _boot_device_from_cmdline(cmdline):
+    """Resolve the boot partition from archiso's kernel args, or None."""
+    args = dict(arg.split("=", 1) for arg in cmdline.split() if "=" in arg)
+    if args.get("archisodevice", "").startswith("/dev/"):
+        return args["archisodevice"]
+    if args.get("archisosearchuuid"):
+        cmd = ["blkid", "-U", args["archisosearchuuid"]]
+    elif args.get("archisolabel"):
+        cmd = ["blkid", "-L", args["archisolabel"]]
+    else:
+        return None
+    result = _run(cmd)
+    if result is None or result.returncode != 0:
+        return None
+    return result.stdout.strip() or None
 
 
 def _boot_disk_name():
     """Return the parent disk name of the live-ISO boot media (e.g. "sdb"), or None.
 
-    On a normal box `/run/archiso/bootmnt` does not exist and we return None,
+    On bare metal booted from USB this is the stick we booted from — we want
-    leaving the device list untouched. On bare metal booted from USB this is
+    to filter it out so the user can't accidentally pick it as the install
-    the stick we booted from — we want to filter it out so the user can't
+    target. Primary source is the mount behind /run/archiso/bootmnt; when
-    accidentally pick it as the install target.
+    that's gone (copytoram unmounts it) fall back to the UUID/label archiso
+    put on the kernel command line.
     """
+    partition = None
+    result = _run(["findmnt", "-no", "SOURCE", "/run/archiso/bootmnt"])
+    if result is not None and result.returncode == 0:
+        partition = result.stdout.strip() or None
+    if partition is None:
         try:
-        result = subprocess.run(
+            partition = _boot_device_from_cmdline(Path("/proc/cmdline").read_text())
-            ["findmnt", "-no", "SOURCE", "/run/archiso/bootmnt"],
+        except OSError:
-            capture_output=True,
+            partition = None
-            text=True,
+    if partition is None:
-        )
-    except FileNotFoundError:
         return None
-    if result.returncode != 0:
+    # A stick written with dd has the ISO filesystem on the whole disk, where
-        return None
+    # PKNAME is empty — the device itself is then the disk.
-    partition = result.stdout.strip()
+    return _parent_disk(partition) or Path(partition).name
-    if not partition:
-        return None
-    try:
-        parent = subprocess.run(
-            ["lsblk", "-no", "PKNAME", partition],
-            capture_output=True,
-            text=True,
-        )
-    except FileNotFoundError:
-        return None
-    if parent.returncode != 0:
-        return None
-    name = parent.stdout.strip().splitlines()[0] if parent.stdout.strip() else ""
-    return name or None
 
 
 def _smart_status(device):
-    try:
+    result = _run(["smartctl", "-H", device])
-        result = subprocess.run(
+    if result is None:
-            ["smartctl", "-H", device],
-            capture_output=True,
-        )
-        output = result.stdout.decode()
-        if "PASSED" in output:
-            return "passed"
-        elif "FAILED" in output:
-            return "failed"
         return "unknown"
-    except Exception as e:
+    if "PASSED" in result.stdout:
-        print(f"Error checking SMART status for {device}: {e}")
+        return "passed"
+    if "FAILED" in result.stdout:
+        return "failed"
     return "unknown"
 
 
@@ -60,40 +94,33 @@ _HEALTH_LABEL = {
     "unknown": "Status unknown",
 }
 
+_TYPE_SCORE = {"NVMe": 15, "SSD": 10, "eMMC": 8, "HDD": 5, "USB": 0}
+
 
 def get_drive_health(device):
     return _HEALTH_SCORE[_smart_status(device)]
 
 
-def get_drive_type_score(device):
+def classify_drive(name, tran="", rota=None, removable=False):
-    name = device.lower()
+    """Human label for a disk: NVMe, SSD, eMMC, HDD or USB.
-    if "nvme" in name:
-        return 15
-    if "ssd" in name:
-        return 10
-    return 5
 
-
+    Uses lsblk's transport and rotational flags — the kernel name alone
-def get_drive_type_label(device):
+    can't tell an SSD from a spinning disk (both are sdX).
-    name = device.lower()
+    """
-    if "nvme" in name:
+    tran = (tran or "").lower()
+    if tran == "usb" or (removable and not name.startswith("mmcblk")):
+        return "USB"
+    if tran == "nvme" or name.startswith("nvme"):
         return "NVMe"
-    if "ssd" in name:
+    if tran == "mmc" or name.startswith("mmcblk"):
+        return "eMMC"
+    if rota is False:
         return "SSD"
     return "HDD"
 
 
-def parse_size_gb(size_str):
+def get_drive_type_score(type_label):
-    size_str = size_str.strip().upper().replace(",", ".")
+    return _TYPE_SCORE.get(type_label, 5)
-    if not size_str:
-        return None
-    if size_str.endswith("T"):
-        return float(size_str[:-1]) * 1024
-    if size_str.endswith("G"):
-        return float(size_str[:-1])
-    if size_str.endswith("M"):
-        return float(size_str[:-1]) / 1024
-    return None
 
 
 def get_size_score(size_gb):
@@ -106,61 +133,98 @@ def get_size_score(size_gb):
     return 10
 
 
-def score_device(device, size_gb):
+def format_size(size_bytes):
-    return get_drive_type_score(device) + get_drive_health(device) + get_size_score(size_gb)
+    gb = size_bytes / 1024**3
+    if gb >= 1024:
+        return f"{gb / 1024:.1f} TB".replace(".0 ", " ")
+    if gb >= 10:
+        return f"{gb:.0f} GB"
+    return f"{gb:.1f} GB"
 
 
-def parse_lsblk_output(output, boot_disk=None):
+def _flag(value):
-    """Parse `lsblk -dn -o NAME,SIZE,TYPE` output into scored device dicts.
+    # util-linux ≥2.37 emits JSON booleans; older builds emit "0"/"1".
+    if isinstance(value, bool):
+        return value
+    return str(value).strip() in ("1", "true")
 
-    Keeps only TYPE=disk so the live ISO's own squashfs (loop) and the boot
+
-    CD-ROM (rom) don't show up as install targets. If `boot_disk` is given,
+def parse_lsblk_json(output, boot_disk=None, uefi=True):
-    that disk is also dropped — it's the USB stick the live ISO booted from
+    """Parse `lsblk -J -d -b -o NAME,SIZE,TYPE,RO,RM,TRAN,ROTA` into device dicts.
-    on bare metal, where it appears as TYPE=disk and would otherwise be a
+
-    valid-looking install target.
+    Keeps only real, writable, non-empty TYPE=disk devices (drops the live
+    ISO's loop/rom, zram, eMMC boot areas, empty card-reader slots) and the
+    USB stick we booted from. Disks too small to install on stay in the list
+    with `usable=False` and a reason so the user sees why they're greyed out.
+    Sorted best-first; unusable disks last.
     """
+    try:
+        entries = json.loads(output or "{}").get("blockdevices", [])
+    except json.JSONDecodeError:
+        return []
     devices = []
-    for line in output.strip().split("\n"):
+    for e in entries:
-        if not line:
+        name = e.get("name") or ""
+        if e.get("type") != "disk" or not name:
             continue
-        parts = line.split()
+        if _PSEUDO_DISK_RE.match(name) or (boot_disk and name == boot_disk):
-        if len(parts) < 3:
             continue
-        name, size, dev_type = parts[0], parts[1], parts[2]
+        try:
-        if dev_type != "disk":
+            size_bytes = int(e.get("size") or 0)
-            continue
+        except (TypeError, ValueError):
-        if boot_disk and name == boot_disk:
+            size_bytes = 0
+        if size_bytes <= 0 or _flag(e.get("ro", False)):
             continue
+        size_gb = size_bytes / 1024**3
+        type_label = classify_drive(
+            name,
+            tran=e.get("tran") or "",
+            rota=_flag(e.get("rota")) if e.get("rota") is not None else None,
+            removable=_flag(e.get("rm", False)),
+        )
         device = f"/dev/{name}"
-        size_gb = parse_size_gb(size)
+        usable = size_gb >= MIN_DISK_GB
-        status = _smart_status(device)
+        status = _smart_status(device) if usable else "unknown"
-        score = get_drive_type_score(device) + _HEALTH_SCORE[status] + get_size_score(size_gb)
+        warning = ""
+        if not uefi and size_gb > MBR_LIMIT_GB:
+            warning = (
+                "This computer starts in legacy (BIOS) mode, which can only use "
+                "the first 2 TB of this disk. Switch the firmware to UEFI to use all of it."
+            )
+        elif type_label == "USB":
+            warning = (
+                "This is a USB drive — it works, but an internal disk is faster and more reliable."
+            )
         devices.append(
             {
                 "name": device,
-                "size": size,
+                "size": format_size(size_bytes),
-                "type_label": get_drive_type_label(device),
+                "size_gb": size_gb,
+                "type_label": type_label,
                 "health_label": _HEALTH_LABEL[status],
-                "score": score,
+                "score": get_drive_type_score(type_label)
+                + _HEALTH_SCORE[status]
+                + get_size_score(size_gb),
+                "usable": usable,
+                "reason": "" if usable else f"Too small — Furtka needs at least {MIN_DISK_GB} GB",
+                "warning": warning,
             }
         )
-    devices.sort(key=lambda d: d["score"], reverse=True)
+    devices.sort(key=lambda d: (d["usable"], d["score"]), reverse=True)
     return devices
 
 
 def list_scored_devices():
-    """Return [{name, size, score}, ...] for all physical disks, highest score first."""
+    """Return [{name, size, score, usable, ...}, ...] for all physical disks, best first."""
-    try:
+    result = _run(["lsblk", "-J", "-d", "-b", "-o", "NAME,SIZE,TYPE,RO,RM,TRAN,ROTA"])
-        result = subprocess.run(
+    if result is None or result.returncode != 0:
-            ["lsblk", "-dn", "-o", "NAME,SIZE,TYPE"],
+        print(f"Error listing devices: {result.stderr if result else 'lsblk unavailable'}")
-            capture_output=True,
-            text=True,
-            check=True,
-        )
-    except subprocess.CalledProcessError as e:
-        print(f"Error listing devices: {e}")
         return []
-    return parse_lsblk_output(result.stdout, boot_disk=_boot_disk_name())
+    return parse_lsblk_json(
+        result.stdout,
+        boot_disk=_boot_disk_name(),
+        uefi=Path("/sys/firmware/efi").exists(),
+    )
 
 
 def main():
@@ -168,11 +232,11 @@ def main():
     if not devices:
         print("No storage devices found.")
         return
-    print(f"\n{'Device':<20} {'Size':<10} {'Score'}")
+    print(f"\n{'Device':<20} {'Size':<10} {'Type':<6} {'Score'}")
-    print("-" * 40)
+    print("-" * 46)
     for d in devices:
-        print(f"{d['name']:<20} {d['size']:<10} {d['score']}")
+        note = "" if d["usable"] else f"  ({d['reason']})"
-    print(f"\nBest drive for boot: {devices[0]['name']} (score {devices[0]['score']})")
+        print(f"{d['name']:<20} {d['size']:<10} {d['type_label']:<6} {d['score']}{note}")
 
 
 if __name__ == "__main__":

webinstaller/static/style.css

@@ -190,9 +190,17 @@ select:focus {
   background: var(--bg-card);
   border: 1px solid var(--border);
   border-radius: 8px;
+  flex-wrap: wrap;
   cursor: pointer;
   transition: border-color 120ms, background 120ms;
 }
+.drive-disabled { cursor: not-allowed; opacity: 0.6; }
+.drive-disabled:hover { border-color: var(--border); }
+.drive .drive-note {
+  flex-basis: 100%;
+  font-size: 0.82rem;
+  color: var(--fg-muted);
+}
 .drive:hover { border-color: color-mix(in srgb, var(--accent) 50%, var(--border)); }
 .drive input[type="radio"] {
   accent-color: var(--accent);

webinstaller/templates/install/overview.html

@@ -22,7 +22,8 @@
     </table>
 </div>
 
-<form method="post" action="{{ url_for('install_run') }}">
+<form method="post" action="{{ url_for('install_run') }}"
+      onsubmit="this.querySelector('button').disabled = true; this.querySelector('button').textContent = 'Starting…';">
     <div class="actions">
         <button type="submit" class="btn btn-danger">Install — wipe drive and proceed</button>
         <a href="{{ url_for('install_step_1') }}" class="btn btn-link">← Start over</a>

webinstaller/templates/install/step2.html

@@ -7,33 +7,47 @@
 <h1>Boot drive</h1>
 <p class="lede">Pick the disk Furtka will install onto. We pre-select the drive that looks fastest and healthiest.</p>
 
-{% if not drives %}
+{% set usable = drives | selectattr("usable") | list %}
+{% set pick = selected if (selected and usable | selectattr("name", "equalto", selected) | list) else (usable[0].name if usable else "") %}
+
+{% if error %}
+<div class="alert alert-error">{{ error }}</div>
+{% endif %}
+
+{% if not usable %}
 <div class="alert alert-error">
-    No physical disks detected. The live ISO can't see any install targets — check your BIOS / SATA controller.
+    {% if drives %}
+    None of the disks in this computer is big enough for Furtka (it needs at least 16 GB).
+    {% else %}
+    No disk found to install onto. Check that the disk is connected, and in the BIOS/UEFI settings
+    that the SATA mode is "AHCI" rather than "RAID" or "Intel RST" — Linux can't see disks in RAID mode.
+    {% endif %}
 </div>
 {% endif %}
 
 <form method="post" action="{{ url_for('install_step_2') }}">
     <div class="drive-list">
         {% for d in drives %}
-        <label class="drive">
+        <label class="drive{% if not d.usable %} drive-disabled{% endif %}">
             <input type="radio" name="boot_drive" value="{{ d.name }}"
-                {% if (selected and d.name == selected) or (not selected and loop.first) %}checked{% endif %} />
+                {% if not d.usable %}disabled{% elif d.name == pick %}checked{% endif %} />
             <span class="name">{{ d.name }}</span>
-            {% if not selected and loop.first %}
+            {% if not selected and d.usable and loop.first %}
             <span class="badge-recommended">Recommended</span>
             {% endif %}
             <span class="meta">
                 <span class="chip">{{ d.size }}</span>
                 <span class="chip">{{ d.type_label }}</span>
-                <span class="chip">{{ d.health_label }}</span>
+                {% if d.usable %}<span class="chip">{{ d.health_label }}</span>{% endif %}
             </span>
+            {% if d.reason %}<span class="drive-note">{{ d.reason }}</span>{% endif %}
+            {% if d.warning %}<span class="drive-note">{{ d.warning }}</span>{% endif %}
         </label>
         {% endfor %}
     </div>
 
     <div class="actions">
-        <button type="submit" class="btn btn-primary" {% if not drives %}disabled{% endif %}>Next — review</button>
+        <button type="submit" class="btn btn-primary" {% if not usable %}disabled{% endif %}>Next — review</button>
         <a href="{{ url_for('install_step_1') }}" class="btn btn-link">← Back</a>
     </div>
 </form>