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Lulo – Udev View

The UDEV page brings rule files, the hardware database, and live device records into one surface – and it does so entirely by reading the filesystem, including the resolved device state in /run/udev/data, with no libudev dependency.

Table of Contents

  1. What the page shows
  2. Three views, three filesystem sources
  3. Rules and Hwdb
  4. Devices: reading the udev runtime database
  5. Editing
  6. See also

1. What the page shows

UDEV is an inspection and configuration surface for device handling. Like the cgroups, systemd, and tune pages it runs on the client/daemon split: a backend thread requests a snapshot from lulod, which gathers the data and caches it (see Process Model & IPC).

Subview Purpose
Rules Installed udev .rules files
Hwdb Installed .hwdb hardware-database files
Devices Live device records from udev’s runtime state

2. Three views, three filesystem sources

Each view is a directory scan or file parse – there is no udevadm subprocess and no libudev linkage.

UDEV: filesystem-only data sources Rules .rules in rule_roots[] Hwdb .hwdb in hwdb_roots[] Devices /run/udev/data records /etc/udev/rules.d, vendor dirs directory scan, suffix filter /etc + /usr/lib udev hwdb.d directory scan, suffix filter resolved device DB E:SUBSYSTEM / DEVNAME / P:syspath

3. Rules and Hwdb

The Rules and Hwdb views are directory listings of their respective roots, filtered by filename suffix (.rules, .hwdb). Both show a two-column list:

Column Meaning
src Source: /etc overrides (green) vs vendor (cyan)
file File name

Selecting a file previews a path / source header followed by a raw dump of the file. The two views share the same preview renderer, so a hwdb file reads exactly like a rule file – header plus contents. This makes the page a fast way to see how device naming, permissions, and properties are actually defined on this system across both vendor and local overrides.

Lulo UDEV Rules view with file list and rule preview
The Rules view: installed rule files with source ranking, and the selected rule file previewed.

4. Devices: reading the udev runtime database

The Devices view is the novel part. Instead of enumerating sysfs or calling libudev, it parses udev’s own resolved runtime database under /run/udev/data. Each file there is a per-device record that udev wrote after processing rules; Lulo reads it line by line, pulling out the subsystem, device node, and syspath.

Column Meaning
subsystem Device subsystem (cyan)
name Derived from devnode, then devpath, then the record filename
devnode Device node path

Selecting a device previews a header (path / subsystem / devnode / syspath) followed by the raw udev-db record, sorted by subsystem then name. Reading /run/udev/data directly is what lets the page show the resolved device state – the properties udev actually assigned – without a libudev dependency or a sysfs crawl.

5. Editing

UDEV uses the shared external-editor handoff, the same model as SCHED and SYSTEMD. Rule and hwdb files expose an edit path; pressing i opens it in $VISUAL / $EDITOR, and privileged writes commit through lulod-system’s atomic, allowlist-scoped edit protocol. The Devices view is not editable – the /run/udev/data records are runtime state, not user-authored config, so there is no edit path for them.

What exists today Not the main workflow yet
Browse rule and hwdb files Rule creation / deletion as a TUI-first flow
Inspect live device records High-level device action tooling
Edit rule and hwdb files A full udevadm replacement

6. See also