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+# Xubuntu Setup — Asus T101HA (`ears-tablet`)
+
+Working notes for setting up an Asus T101HA (Atom x5-Z8350, 2 GB RAM / ~1.8 GB
+usable, eMMC) as a Mono + GTK#3 development and runtime machine.
+
+User: `ears` · Hostname: `ears-tablet`
+
+---
+
+## Contents
+
+- [0. Recommended baseline](#0-recommended-baseline)
+- [1. Installing Xubuntu](#1-installing-xubuntu)
+  - [1.1 Check firmware bitness first](#11-check-firmware-bitness-first--this-determines-everything)
+  - [1.2 Build the USB](#12-build-the-usb)
+  - [1.3 BIOS](#13-bios)
+  - [1.4 Install](#14-install)
+  - [1.5 Post-install GRUB fix (IA32 only)](#15-post-install-grub-fix-ia32-machines-only)
+  - [1.6 Expect to fix afterwards](#16-expect-to-fix-afterwards)
+- [2. First boot / recovery mode](#2-first-boot--recovery-mode)
+- [3. Low-RAM tuning](#3-low-ram-tuning)
+  - [Option A — `zram-tools`](#option-a--zram-tools-simple)
+  - [Option B — `systemd-zram-generator`](#option-b--systemd-zram-generator-current-preferred-on-2404)
+  - [Swappiness](#swappiness)
+- [4. apt: repair and sources](#4-apt-repair-and-sources)
+  - [4.1 The modern layout](#41-the-modern-layout)
+  - [4.2 Correct stock sources](#42-correct-stock-sources-2510-example--substitute-your-codename)
+  - [4.3 Which host? archive vs old-releases](#43-which-host-archive-vs-old-releases)
+  - [4.4 Check for genuinely broken packages](#44-check-for-genuinely-broken-packages)
+  - [4.5 Don't do these](#45-dont-do-these)
+  - [4.6 `full-upgrade` checklist](#46-full-upgrade-checklist)
+  - [4.7 Reboot needed?](#47-reboot-needed)
+- [5. Mono + GTK#3](#5-mono--gtk3)
+  - [Install](#install)
+  - [Optional](#optional)
+  - [Verify](#verify)
+  - [Smoke test](#smoke-test)
+  - [Notes vs. the WSL guide](#notes-vs-the-wsl-guide)
+- [6. Display rotation + touchscreen](#6-display-rotation--touchscreen)
+  - [Identify devices](#identify-devices)
+  - [Matrices](#matrices)
+  - [Persistence script](#persistence-script)
+  - [Login screen (LightDM)](#login-screen-lightdm--separate-from-your-session)
+  - [Better: rotate before the session starts](#better-rotate-before-the-session-starts)
+  - [Wallpaper breaks after rotating](#wallpaper-breaks-after-rotating)
+  - [Auto-rotation (optional)](#auto-rotation-optional)
+- [7. Audio](#7-audio)
+  - [Install and test](#install-and-test)
+  - [Choosing the right card](#choosing-the-right-card)
+  - [Renumbering at the kernel level](#renumbering-at-the-kernel-level)
+  - [Caveats](#caveats)
+- [8. Running a script at boot](#8-running-a-script-at-boot)
+- [9. File transfer to/from Windows](#9-file-transfer-tofrom-windows)
+- [10. Quick reference](#10-quick-reference)
+
+---
+
+## 0. Recommended baseline
+
+**Target: Xubuntu 24.04 LTS (Minimal ISO).**
+
+Reasons, from the apt/Mono investigation:
+- The machine was found running **Ubuntu 25.10 "questing"**, which hit end of
+  life on **9 July 2026**. No further updates will ever be published for it.
+- `gtk-sharp3` is **not packaged on 25.10**, and upgrading to 26.04 would not
+  bring it back.
+- `gtk-sharp3` **is** packaged on 24.04 (noble), supported to 2029.
+- Xfce on 24.04 idles around 500–600 MB, which matters at 1.8 GB RAM.
+
+Mono + `mcs` + GTK# is the correct toolchain for this hardware — the .NET SDK
+(~800 MB) and Avalonia are far heavier.
+
+Before reinstalling, back up: `*.cs`, `*.glade`, SSH keys, browser profile.
+
+```bash
+lsblk            # is /home a separate partition?
+df -h /
+free -h
+mkdir -p ~/backup && cp ~/*.cs ~/*.glade ~/backup/
+```
+
+If `/home` is its own partition, it can be preserved during install (assign
+`/home` **without** format). Use the same username to keep permissions clean.
+
+---
+
+## 1. Installing Xubuntu
+
+### 1.1 Check firmware bitness first — this determines everything
+
+In Windows: **Settings → System → About → System type**
+
+- *32-bit operating system, x64-based processor* → **IA32 UEFI**, needs the
+  bootia32 workaround below.
+- *64-bit* → skip the GRUB steps.
+
+### 1.2 Build the USB
+
+Ventoy includes IA32 UEFI support, so try it first. If it won't boot, fall back
+to Rufus and copy a 32-bit `bootia32.efi` (GRUB) into `/EFI/BOOT` on the stick.
+
+From Linux, writing directly:
+
+```bash
+sudo dd if=xubuntu-24.04-minimal-amd64.iso of=/dev/sdX bs=4M status=progress conv=fsync
+```
+
+> Verify the target with `lsblk` first. `dd` to the wrong disk destroys it
+> silently.
+
+Verify the ISO: `sha256sum` against the checksum on the download page.
+
+### 1.3 BIOS
+
+- F2 at power-on
+- **Disable Secure Boot** (the ia32 GRUB is unsigned)
+- Boot menu is usually F12 / Esc
+
+### 1.4 Install
+
+Choose **Install**, not *Try* — the live session eats RAM you don't have.
+Don't open Firefox or anything else during install. Let it create swap.
+
+### 1.5 Post-install GRUB fix (IA32 machines only)
+
+The installer writes a 64-bit `grubx64.efi` the firmware can't read. Boot the
+live session, chroot in, and:
+
+```bash
+grub-install --target=i386-efi --efi-directory=/boot/efi
+```
+
+This is **not optional** on IA32 firmware.
+
+### 1.6 Expect to fix afterwards
+
+| Component | Notes |
+|---|---|
+| Wi-Fi | RTL8723BS SDIO — finicky |
+| Audio | ESS ES8316 codec, needs UCM configs |
+| Touchscreen | Works, but rotation needs manual matrix (§6) |
+| Auto-rotation | Needs `iio-sensor-proxy` + custom handler |
+
+A recent 6.x kernel fixes most of these.
+
+---
+
+## 2. First boot / recovery mode
+
+If the user account lacks admin rights:
+
+```bash
+usermod -aG sudo ears
+groups ears                       # confirm 'sudo' appears
+hostnamectl set-hostname ears-tablet
+localectl set-locale LANG=en_US.UTF-8   # optional, cosmetic
+exit                              # then 'resume'
+```
+
+`usermod -aG sudo` is the one that isn't optional — without it you can log in
+but can't run any admin command.
+
+---
+
+## 3. Low-RAM tuning
+
+### Option A — `zram-tools` (simple)
+
+```bash
+sudo apt install zram-tools
+```
+
+Edit `/etc/default/zramswap`:
+```
+PERCENT=60
+ALGO=zstd
+```
+
+### Option B — `systemd-zram-generator` (current, preferred on 24.04+)
+
+```bash
+sudo apt install systemd-zram-generator
+
+sudo tee /etc/systemd/zram-generator.conf > /dev/null <<'EOF'
+[zram0]
+zram-size = min(ram / 2, 4096)
+compression-algorithm = zstd
+swap-priority = 100
+EOF
+
+sudo systemctl daemon-reload
+sudo systemctl start systemd-zram-setup@zram0.service
+swapon --show     # expect /dev/zram0
+zramctl
+```
+
+The package does nothing without a config file containing at least one section.
+
+### Swappiness
+
+Swapping to zram is cheap, so raise it so the kernel actually uses it:
+
+```bash
+echo 'vm.swappiness=100' | sudo tee /etc/sysctl.d/99-zram.conf
+```
+
+Reboot. Verdict: worth it at 2–4 GB, marginal at 8 GB, skip above 16 GB.
+zram compresses **RAM** — it does nothing for low disk space.
+
+---
+
+## 4. apt: repair and sources
+
+### 4.1 The modern layout
+
+Since 24.04, archive config lives in **`/etc/apt/sources.list.d/ubuntu.sources`**
+(deb822 format). `/etc/apt/sources.list` being empty is normal, not a symptom.
+Most apt advice online predates this and edits a file that does nothing.
+
+### 4.2 Correct stock sources (25.10 example — substitute your codename)
+
+```bash
+sudo tee /etc/apt/sources.list.d/ubuntu.sources > /dev/null <<'EOF'
+Types: deb
+URIs: http://archive.ubuntu.com/ubuntu/
+Suites: questing questing-updates questing-backports
+Components: main restricted universe multiverse
+Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg
+
+Types: deb
+URIs: http://security.ubuntu.com/ubuntu/
+Suites: questing-security
+Components: main restricted universe multiverse
+Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg
+EOF
+
+sudo apt update
+```
+
+Do not drop the `Signed-By:` line — without it apt falls back to the legacy
+trusted-keyring and you get confusing "not signed" errors later.
+
+`ubuntu.sources.curtin.orig` is the installer's pristine backup. apt ignores
+`.orig` files. Useful as a reference, don't copy blindly.
+
+### 4.3 Which host? archive vs old-releases
+
+An EOL release only moves to `old-releases.ubuntu.com` when the migration
+actually runs — which can lag the EOL date by weeks. Pointing there too early
+gives four clean 404s. Test before switching:
+
+```bash
+for p in questing questing-updates questing-backports questing-security; do
+  echo -n "$p: "
+  curl -sI "http://old-releases.ubuntu.com/ubuntu/dists/$p/Release" | head -1
+done
+
+curl -sI http://archive.ubuntu.com/ubuntu/dists/questing/Release | head -1
+```
+
+`200` = pocket exists. `404` = drop it or use the other host.
+
+### 4.4 Check for genuinely broken packages
+
+All read-only, cheapest first:
+
+```bash
+sudo dpkg --audit          # clean = no output at all
+sudo apt-get check         # verifies the dependency tree
+dpkg -l | grep -v '^ii' | grep -v '^rc'
+apt-mark showhold          # held packages are silently skipped on upgrade
+```
+
+dpkg status codes (desired state, then actual):
+
+| Code | Meaning |
+|---|---|
+| `ii` | Healthy |
+| `rc` | Removed, config left — harmless |
+| `iU` | Unpacked, never configured |
+| `iF` | Half-configured |
+| `iH` | Half-installed |
+| `iW` / `it` | Waiting on / pending triggers |
+| `*R*` | Reinstall required → `apt install --reinstall <name>` |
+
+Then repair:
+
+```bash
+sudo dpkg --configure -a
+sudo apt --fix-broken install
+sudo apt full-upgrade
+```
+
+### 4.5 Don't do these
+
+```bash
+# WRONG — killall receives 'sudo', 'rm', paths etc. as process names
+sudo killall apt apt-get dpkg 2>/dev/null sudo rm /var/lib/apt/lists/lock ...
+
+# DANGEROUS — rm -rf also targets files named sudo, apt, clean, update in $PWD
+sudo rm -rf /var/lib/apt/lists/* sudo apt clean sudo apt update
+```
+
+These must be separate lines. Also: killing `dpkg` mid-transaction is what
+*creates* the broken state. Check first with `ps aux | grep -E 'apt|dpkg'`.
+
+Don't remove `universe` — it's an Ubuntu component, not a PPA, and
+`gtk-sharp3` lives there. And never run
+`add-apt-repository --remove ppa:repository-name/ppa` literally; that's a
+placeholder from a copied guide.
+
+### 4.6 `full-upgrade` checklist
+
+- Use `full-upgrade`, not `upgrade` — it permits removals where deps changed
+- Read the summary line; mass removals of desktop/kernel packages = stop
+- Plug the tablet in; power loss mid-`dpkg` recreates the broken state
+- On config prompts, keeping the local version (the default) is safe unless
+  you know you edited it
+- Then `sudo apt autoremove` — but answer `n` if anything with `efi` appears
+- Reboot before `do-release-upgrade` so the newest kernel is running
+
+### 4.7 Reboot needed?
+
+```bash
+[ -f /var/run/reboot-required ] && cat /var/run/reboot-required.pkgs
+sudo needrestart     # interactive; shows what's running old libs
+```
+
+Kernel / initramfs / systemd / glibc → reboot. Everything else → restart the
+service.
+
+---
+
+## 5. Mono + GTK#3
+
+### Install
+
+```bash
+sudo add-apt-repository universe
+sudo apt update
+sudo apt install mono-complete gtk-sharp3
+```
+
+| Package | Contents | Size |
+|---|---|---|
+| `mono-runtime` | JIT + `mscorlib` only | ~15 MB |
+| `mono-devel` | Compiler + the BCL you need | ~200–400 MB |
+| `mono-complete` | Runtime + `mcs` + entire class library + F#/VB | ~300–500 MB |
+
+**Avoid `mono-runtime`.** The BCL is split across dozens of
+`libmono-system-*-cil` packages; hello-world runs, but anything touching LINQ,
+XML, HTTP, or `System.IO.Ports` (the COM-port combo box in `homepage.glade`)
+throws `Could not load file or assembly`. On a tight disk, `mono-devel` saves
+~100 MB over `mono-complete` and still covers everything this project needs.
+
+### Optional
+
+```bash
+sudo apt install glade         # visual designer — skip on this machine
+sudo apt install libgdiplus    # only if using System.Drawing
+sudo apt install libcanberra-gtk3-module   # silences a harmless console warning
+```
+
+### Verify
+
+```bash
+mono --version
+mcs --version
+pkg-config --list-all | grep gtk-sharp     # want gtk-sharp-3.0
+apt policy gtk-sharp3
+```
+
+### Smoke test
+
+```bash
+cat > gtkcheck.cs <<'EOF'
+using System;
+using Gtk;
+
+class GtkCheck {
+    static void Main() {
+        Application.Init();
+        var win = new Window("Hello GTK#3");
+        win.SetDefaultSize(300, 200);
+        win.DeleteEvent += (o, args) => Application.Quit();
+
+        var button = new Button("Click me");
+        button.Clicked += (o, args) => Console.WriteLine("Clicked!");
+        win.Add(button);
+
+        win.ShowAll();
+        Application.Run();
+    }
+}
+EOF
+
+mcs -pkg:gtk-sharp-3.0 gtkcheck.cs
+mono gtkcheck.exe
+```
+
+Do the throwaway test first — it isolates "is gtk-sharp3 working" from "does my
+app compile."
+
+Then the real thing:
+
+```bash
+mcs -pkg:gtk-sharp-3.0 program.cs MainWindow.cs ArduinoConnection.cs -out:test.exe
+mono test.exe
+```
+
+(`ArduinoConnection.cs` is needed because `MainWindow` calls
+`_arduino.Disconnect()`; omitting it gives `CS0246`.)
+
+### Notes vs. the WSL guide
+
+- No WSLg, no `$DISPLAY` fiddling — Xfce is itself GTK3, so the app picks up the
+  system theme and the window just appears.
+- Only exception: over SSH you need `ssh -X`.
+- Companion files (`-r:` DLLs, `homepage.glade`) must sit next to the `.exe`, or
+  you get `FileNotFoundException`.
+- `homepage.glade` targets GTK 3.24, which 22.04 and 24.04 both ship.
+- `gtk-sharp2` is gone from 24.04 onward — use `gtk-sharp3`.
+
+---
+
+## 6. Display rotation + touchscreen
+
+X11 does **not** rotate touch input when you rotate the display. The touch
+device needs its own coordinate transformation matrix.
+
+### Identify devices
+
+```bash
+xrandr                          # output name — DSI-1, or None-1 on this unit
+xinput list --name-only         # look for Silead / GSL / SIS, NOT 'Touchpad'
+```
+
+> On this tablet the output reported as **`None-1`** (xrandr's fallback when the
+> connector type isn't identified — it can change between kernels) and the
+> touchscreen as **`SIS0457:00 0457:11ED`**.
+
+### Matrices
+
+| Rotation | Matrix |
+|---|---|
+| normal | `1 0 0 0 1 0 0 0 1` |
+| right (90° CW) | `0 1 0 -1 0 1 0 0 1` |
+| left (90° CCW) | `0 -1 1 1 0 0 0 0 1` |
+| inverted (180°) | `-1 0 1 0 -1 1 0 0 1` |
+
+```bash
+xrandr --output None-1 --rotate right
+xinput set-prop "SIS0457:00 0457:11ED" "Coordinate Transformation Matrix" 0 1 0 -1 0 1 0 0 1
+```
+
+### Persistence script
+
+```bash
+nano ~/rotate.sh
+```
+
+```bash
+#!/bin/bash
+sleep 3
+OUT=$(xrandr | awk '/ connected/{print $1; exit}')
+xrandr --output "$OUT" --rotate right
+TS=$(xinput list --name-only | grep -iE 'silead|gsl|touchscreen|SIS' | grep -vi 'touchpad' | head -1)
+[ -n "$TS" ] && xinput set-prop "$TS" "Coordinate Transformation Matrix" 0 1 0 -1 0 1 0 0 1
+xset s off
+xset -dpms
+```
+
+```bash
+chmod +x ~/rotate.sh
+~/rotate.sh          # test before automating
+```
+
+Then **Settings → Session and Startup → Application Autostart → Add**, command
+`/home/ears/rotate.sh`.
+
+> **Gotcha:** grepping bare `touch` matches the **trackpad** and rotates the
+> pointer instead. Use `touchscreen` and exclude `touchpad`. To undo:
+> ```bash
+> TP=$(xinput list --name-only | grep -i -m1 touchpad)
+> xinput set-prop "$TP" "Coordinate Transformation Matrix" 1 0 0 0 1 0 0 0 1
+> ```
+> Or just log out — the matrix isn't saved anywhere.
+
+The `sleep 3` matters; the touchscreen isn't registered the instant the session
+starts. Raise to 5 if touch still comes out wrong.
+
+**Try Settings → Display first.** Its rotation dropdown often persists on its
+own, leaving the script to handle only the `xinput` part.
+
+### Login screen (LightDM — separate from your session)
+
+```bash
+sudo nano /etc/lightdm/lightdm.conf
+```
+```ini
+[Seat:*]
+display-setup-script=/usr/bin/xrandr --output None-1 --rotate right
+```
+
+### Better: rotate before the session starts
+
+```bash
+sudo nano /etc/X11/xorg.conf.d/10-monitor.conf
+```
+```
+Section "Monitor"
+    Identifier "DSI-1"
+    Option "Rotate" "right"
+EndSection
+```
+
+Whole machine including the text console — add to `/etc/default/grub`:
+`fbcon=rotate:1` plus `video=DSI-1:panel_orientation=right_side_up`, then
+`sudo update-grub`.
+
+### Wallpaper breaks after rotating
+
+The desktop paints the wallpaper onto a surface sized for the old geometry and
+doesn't repaint after `xrandr`. On Xfce:
+
+```bash
+xfdesktop --reload
+```
+
+Also set the image style to **scaled** — `spanned` and `zoom` misbehave badly
+when the aspect ratio flips. Rotating before the session starts avoids this
+entirely.
+
+### Auto-rotation (optional)
+
+Xfce has no built-in handler. Confirm the sensor works before writing anything:
+
+```bash
+sudo apt install -y iio-sensor-proxy
+monitor-sensor        # tilt the tablet; orientation should print
+```
+
+If nothing prints, this unit needs a kernel quirk — not worth chasing.
+
+```bash
+monitor-sensor | while read -r line; do
+  case "$line" in
+    *normal*)    R=normal;   M="1 0 0 0 1 0 0 0 1" ;;
+    *right-up*)  R=right;    M="0 1 0 -1 0 1 0 0 1" ;;
+    *left-up*)   R=left;     M="0 -1 1 1 0 0 0 0 1" ;;
+    *bottom-up*) R=inverted; M="-1 0 1 0 -1 1 0 0 1" ;;
+    *) continue ;;
+  esac
+  xrandr --output DSI-1 --rotate "$R"
+  xinput set-prop "SIS0457:00 0457:11ED" "Coordinate Transformation Matrix" $M
+done
+```
+
+> Most community auto-rotate scripts only call `xrandr` and leave touch behind.
+> If a script doesn't contain `xinput set-prop`, it won't rotate touch.
+
+---
+
+## 7. Audio
+
+### Install and test
+
+```bash
+sudo apt install alsa-utils      # this is what provides aplay
+
+aplay --version
+aplay -l                          # list playback devices
+aplay /usr/share/sounds/alsa/Front_Center.wav
+speaker-test -c 2 -t wav -l 1
+```
+
+PipeWire/PulseAudio layer:
+
+```bash
+pactl info                  # "Server Name" tells you which
+pactl list short sinks
+paplay /usr/share/sounds/alsa/Front_Center.wav
+```
+
+### Choosing the right card
+
+Neither config file exists by default — create whichever you prefer:
+
+```bash
+nano ~/.asoundrc              # per-user; wins over the system file
+# or
+sudo nano /etc/asound.conf    # system-wide, incl. root and systemd services
+```
+
+```
+defaults.pcm.card 1
+defaults.ctl.card 1
+```
+
+`ctl` is what `alsamixer` reads, `pcm` is what `aplay` reads — set both. No
+reload needed; it's read per-process.
+
+With `plughw` conversion behaviour as the default:
+
+```
+pcm.!default {
+    type plug
+    slave.pcm "hw:1,0"
+}
+ctl.!default {
+    type hw
+    card 1
+}
+```
+
+Verify — `-v` prints the resolved device:
+
+```bash
+aplay -D default -v /usr/share/sounds/alsa/Front_Center.wav 2>&1 | head -20
+```
+
+### Renumbering at the kernel level
+
+```bash
+cat /proc/asound/modules
+sudo nano /etc/modprobe.d/alsa-card-order.conf
+```
+```
+options snd_soc_sst_bytcr_rt5640 index=0
+options snd_hda_intel index=1
+```
+```bash
+sudo update-initramfs -u && sudo reboot
+```
+
+### Caveats
+
+- **PipeWire ignores all of the above.** `~/.asoundrc` only governs programs
+  talking to ALSA directly (`aplay`, `alsamixer`). For desktop apps use
+  `pactl set-default-sink` or `pavucontrol`.
+- Save your mixer levels or they come back muted: `sudo alsactl store 1`
+- Device busy → use `aplay -D default file.wav`, not `-D hw:0,0`
+- Permission errors → `sudo usermod -aG audio $USER`, then re-login
+- `aplay` handles WAV/AU/RAW only — use `mpg123` or `ffplay` for MP3/FLAC
+
+---
+
+## 8. Running a script at boot
+
+```bash
+sudo nano /usr/local/bin/myscript.sh
+sudo chmod +x /usr/local/bin/myscript.sh
+```
+
+Start with `#!/bin/bash` and use **absolute paths** — there's almost no
+environment at boot.
+
+```bash
+sudo nano /etc/systemd/system/myscript.service
+```
+
+```ini
+[Unit]
+Description=My boot script
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+ExecStart=/usr/local/bin/myscript.sh
+RemainAfterExit=yes
+
+[Install]
+WantedBy=multi-user.target
+```
+
+```bash
+sudo systemctl daemon-reload
+sudo systemctl enable --now myscript.service
+systemctl status myscript.service
+journalctl -u myscript.service
+```
+
+Variations:
+
+- Long-running daemon → `Type=simple`, drop `RemainAfterExit`
+- Before the login screen → `Before=display-manager.service` in `[Unit]`,
+  `WantedBy=display-manager.service` in `[Install]`
+- Quick and dirty → `sudo crontab -e`, then
+  `@reboot /usr/local/bin/myscript.sh` (no logging, no ordering)
+- Drop `After=`/`Wants=` if networking isn't needed — it'll run earlier
+
+> **A root systemd service cannot rotate the display** — no `DISPLAY`, no
+> `XAUTHORITY`. Use the config-level methods in §6 instead. Same for audio: a
+> root service has no audio session, so use `systemctl --user` or target the
+> hardware device directly.
+
+---
+
+## 9. File transfer to/from Windows
+
+**Tailscale is not required.** It creates a private network *across the
+internet* — only needed to reach the tablet from outside your home. For a
+tablet and PC on the same Wi-Fi it's just another background daemon on a
+2 GB machine.
+
+Lightest option — SSH:
+
+```bash
+sudo apt install -y openssh-server
+```
+
+Connect from Windows with WinSCP or `scp` in PowerShell. No configuration
+beyond the above.
+
+Samba is only worth it if you want the tablet's folders to appear in Windows
+Explorer as a normal network drive.
+
+---
+
+## 10. Quick reference
+
+```bash
+# state
+free -h; df -h /; lsblk; swapon --show
+cat /etc/os-release
+. /etc/os-release; echo $VERSION_CODENAME
+
+# apt health
+sudo dpkg --audit; sudo apt-get check; apt-mark showhold
+ls /etc/apt/sources.list.d/
+cat /etc/apt/sources.list.d/ubuntu.sources
+
+# display
+xrandr; xinput list --name-only
+~/rotate.sh; xfdesktop --reload
+
+# audio
+aplay -l; pactl list short sinks
+aplay /usr/share/sounds/alsa/Front_Center.wav
+sudo alsactl store 1
+
+# build
+mcs -pkg:gtk-sharp-3.0 program.cs MainWindow.cs ArduinoConnection.cs -out:test.exe
+mono test.exe
+```
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