Installer implemented in the live CD! However we still need to add some old realtek network card support for r1

board/mentalnet/INSTALL-GUIDE.md

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+# Mentalnet GNU/Linux — Install & Test Guide
+
+Mentalnet GNU/Linux is a small, TTY-only distribution for 90s Intel
+Pentium-class PCs, built with Buildroot 2025.02.17. The ISO is a live
+CD: the entire system runs from the CD with a read-only root, and the
+same CD carries a built-in hard disk installer (`mentalnet-install`).
+
+- Kernel: `6.12.104-mentalnet-intel32` (slimmed i386 config)
+- Login: `root` / `mnlinux`
+- Hostname: `mentalnet`
+- Live CD size: ~100 MB
+
+---
+
+## 1. System requirements
+
+### Running the live CD
+
+| Component   | Requirement                                              |
+|-------------|----------------------------------------------------------|
+| CPU         | i586 (generic Pentium) or any newer x86                  |
+| RAM         | 128 MB minimum (64 MB usually works)                      |
+| CD drive    | IDE/ATAPI CD-ROM (PIIX-era ATA controller)                |
+| Display     | VGA text console, PS/2 keyboard/mouse                     |
+| USB         | USB keyboards, mice and mass storage (UHCI/OHCI/EHCI)     |
+| Serial      | 8250 UART (kernel log is mirrored to COM1)                |
+| NICs (opt.) | NE2000-PCI clones (RTL8029 etc.), Intel e100/e1000/e1000e, Realtek 8139, 3Com 3c59x |
+
+### Installing to a hard disk
+
+- IDE/ATA disk with at least **400 MB** free (the whole disk is wiped)
+- The machine must be able to boot from CD (El Torito, BIOS boot)
+
+---
+
+## 2. What's on the media
+
+The live system mounts its root filesystem **read-only** from the CD.
+Everything writable lives in RAM:
+
+- `/tmp`, `/run`, `/dev/shm` are tmpfs
+- `/var/log`, `/var/run`, `/var/cache`, `/var/spool`, `/var/tmp`
+  are symlinks into those tmpfs areas
+
+Services started at boot:
+
+| Service    | Purpose                                        |
+|------------|------------------------------------------------|
+| DHCP       | `eth0` configured via udhcpc                   |
+| syslogd    | kernel + system logging (to `/tmp/log`)        |
+| lighttpd   | web server, port 80                            |
+| dropbear   | SSH server, port 22                            |
+| chronyd    | NTP time sync                                  |
+| crond      | cron daemon                                    |
+| iptables   | firewall rules                                 |
+
+DNS from DHCP works on the live CD too: `/etc/resolv.conf` is a
+symlink into tmpfs that `udhcpc` writes through.
+
+---
+
+## 3. Building from source
+
+The build tree is a standard Buildroot 2025.02.17 checkout with the
+Mentalnet configuration applied. Install the usual Buildroot host
+dependencies (see `docs/manual/prerequisite.txt` in the Buildroot
+manual), then:
+
+```
+make
+```
+
+Build outputs land in `output/images/`:
+
+| File              | Purpose                                          |
+|-------------------|--------------------------------------------------|
+| `rootfs.iso9660`  | the bootable live CD / installer ISO             |
+| `bzImage`         | the kernel (also inside the ISO and ext2 image)  |
+| `rootfs.ext2`     | 2 GB raw disk image variant (for QEMU testing)   |
+| `grub-eltorito.img` / `grub.img` | GRUB core images (used by the ISO) |
+
+A full build takes a while; rebuilds after config changes are much
+faster. After editing kernel fragments or the overlay, plain `make`
+picks the changes up.
+
+---
+
+## 4. Testing in QEMU
+
+All commands are run from the Buildroot tree root. Exit a
+`-nographic` session with `Ctrl-A x`.
+
+### 4.1 Live CD, graphical window
+
+```
+qemu-system-i386 -m 128 -cdrom output/images/rootfs.iso9660
+```
+
+Expect the GRUB menu ("Mentalnet GNU/Linux", 10s timeout), a kernel
+boot and a login prompt on the VGA console.
+
+### 4.2 Headless (serial console)
+
+```
+qemu-system-i386 -m 128 -nographic \
+  -kernel output/images/bzImage \
+  -append "console=ttyS0 root=/dev/sr0 ro" \
+  -cdrom output/images/rootfs.iso9660
+```
+
+This bypasses GRUB and shows the whole boot on the terminal.
+
+### 4.3 Low-memory margin test
+
+Same as 4.2 but with `-m 64`. The live system should still come up.
+
+### 4.4 NE2000 network test
+
+```
+qemu-system-i386 -m 128 -nographic -nic model=ne2k_pci \
+  -kernel output/images/bzImage \
+  -append "console=ttyS0 root=/dev/sr0 ro" \
+  -cdrom output/images/rootfs.iso9660
+```
+
+After login, `ip link` should show a configured `eth0`.
+
+### 4.5 Disk image variant
+
+```
+qemu-system-i386 -m 128 -nographic \
+  -kernel output/images/bzImage \
+  -append "console=ttyS0 root=/dev/sda1 rootwait rw" \
+  -drive file=output/images/rootfs.ext2,format=raw,if=ide
+```
+
+(`rootfs.ext2` also contains `/boot/bzImage` and a GRUB config for
+disk boot.)
+
+### 4.6 Full installer end-to-end test
+
+```
+# 1. create a throwaway disk
+qemu-img create -f qcow2 /tmp/mn-test.qcow2 512M
+
+# 2. boot the live CD with the test disk attached
+qemu-system-i386 -m 128 -nographic \
+  -kernel output/images/bzImage \
+  -append "console=ttyS0 root=/dev/sr0 ro" \
+  -cdrom output/images/rootfs.iso9660 \
+  -drive file=/tmp/mn-test.qcow2,format=qcow2,if=ide
+```
+
+Log in and run `mentalnet-install`:
+
+```
+Disk to install to (e.g. sda): sda
+Type YES to continue: YES
+Create a swap partition? [y/N]: y
+```
+
+When it prints `Installation complete!`:
+
+```
+poweroff
+```
+
+Then boot **only** the test disk (no `-cdrom`, no `-kernel`) — this
+exercises the installed GRUB in the MBR:
+
+```
+qemu-system-i386 -m 128 -nographic \
+  -drive file=/tmp/mn-test.qcow2,format=qcow2,if=ide
+```
+
+The kernel log (mirrored to the serial console by the installed
+config) should show `EXT4-fs (sda1): mounted ... r/w` and
+`Run /sbin/init as init process`.
+
+---
+
+## 5. Installing to a hard disk (real hardware)
+
+> **WARNING: the installer destroys ALL data on the target disk
+> without further notice.** Double-check the disk name before
+> confirming.
+
+1. Boot the machine from the CD (El Torito boot).
+2. Log in as `root` (password `mnlinux`).
+3. Run:
+
+   ```
+   mentalnet-install
+   ```
+
+4. Answer the prompts:
+   - **Disk to install to** — e.g. `sda` (the installer lists
+     detected disks with their sizes first)
+   - **Type YES** — destroys everything on that disk
+   - **Create a swap partition? [y/N]** — recommended on machines
+     with little RAM; the swap is sized at 2x RAM, capped at 512 MB
+
+5. The installer then:
+   - writes a fresh MBR partition table (root partition starts at
+     sector 2048, leaving room for the GRUB core image)
+   - creates an ext4 filesystem labelled `rootfs` (+ swap if chosen)
+   - copies the whole system from the CD
+   - generates `/etc/fstab`
+   - installs GRUB to the MBR and writes the boot menu
+
+6. When it prints `Installation complete!`:
+
+   ```
+   poweroff
+   ```
+
+   Remove the CD and power on — the machine now boots from its own
+   disk.
+
+The installed GRUB menu has a 5s timeout and boots automatically.
+
+---
+
+## 6. Post-install notes
+
+- The installed root filesystem is **read-write**, so all services
+  behave normally: chrony keeps its drift file, dropbear generates
+  SSH host keys on first boot, logs persist under `/var/log`.
+- DHCP DNS works the same way as on the live CD (`resolv.conf`
+  symlink into tmpfs).
+- Kernel boot messages are mirrored to `COM1` (ttyS0) — handy for
+  debugging headless or semi-broken machines.
+- Login is `root` / `mnlinux` (same as the live system).
+
+---
+
+## 7. Troubleshooting
+
+| Symptom | Likely cause / fix |
+|---------|--------------------|
+| GRUB menu does not appear, or the machine reboots before booting, in QEMU | Try more RAM (`-m 256`). Memory pressure during development was the culprit more than once. |
+| Kernel panic: `Unable to mount root fs` | The CD drive is on an unsupported controller. The kernel targets PIIX-era IDE/ATA; modern SATA-only setups are out of scope. |
+| `Remounting root filesystem read-write ... failed` on live boot | Cosmetic. The CD root is read-only by design; all writes go to tmpfs. |
+| Installer: `/dev/sdX1 did not appear after partitioning` | The kernel was still re-reading the partition table. Simply run the installer again. |
+| Installer: `disk is too small` | At least 400 MB is needed. |
+| Forgot the password | It is `mnlinux` (set at build time in the Buildroot config). |
+| No network | Check the NIC against the supported list in section 1. QEMU: use `-nic model=ne2k_pci` or the default e1000. |
+
+---
+
+## 8. Maintainer file map
+
+Everything Mentalnet-specific lives here:
+
+| File | Purpose |
+|------|---------|
+| `board/mentalnet/grub-embedded.cfg` | config embedded into the GRUB core image: searches for the medium containing `/boot/bzImage` instead of hardcoding a device |
+| `board/mentalnet/linux-slim.config` | kernel config fragment: keeps the classic PCI NICs, ATA/ATAPI, USB HID/storage, serial and VGA console; drops wireless, sound, DRM, RAID, PCMCIA, debug |
+| `board/mentalnet/overlay/usr/sbin/mentalnet-install` | the hard disk installer |
+| `board/mentalnet/overlay/usr/share/mentalnet/grub-disk.cfg` | boot menu template written to installed systems (`@ROOTDEV@` is replaced) |
+| `board/mentalnet/overlay/etc/resolv.conf` | symlink so DHCP DNS works on the read-only CD |
+| `board/mentalnet/overlay/etc/lighttpd/` | web server configuration |
+| `fs/iso9660/grub.cfg` | live CD boot menu (`root=/dev/sr0 ro`) |
+| `localversion.config` | kernel version suffix (`-mentalnet-intel32`) |
+| `.config` | Buildroot configuration: GRUB2 embedded config path and module list, kernel fragment list, e2fsprogs/grub install tools |

board/mentalnet/overlay/usr/sbin/mentalnet-install

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+#!/bin/sh
+#
+# mentalnet-install - install Mentalnet GNU/Linux from the live CD onto a hard disk
+#
+# Run as root on the live system:  mentalnet-install
+#
+# The installed system boots from its own MBR (GRUB) with the root
+# filesystem on a single ext4 partition (plus optional swap).
+
+set -u
+
+MIN_DISK_SECTORS=819200		# 400 MiB minimum target disk
+BOOT_START_SECTORS=2048		# first sector of root: leaves the MBR gap
+				# free for the GRUB core.img embedding
+MNT=/mnt/hd
+
+msg()	{ printf '%s\n' "$*"; }
+warn()	{ printf 'WARNING: %s\n' "$*"; }
+die()	{ printf 'ERROR: %s\n' "$*" >&2; exit 1; }
+
+# make sure a failed run never leaves the target disk mounted
+cleanup() {
+	grep -q " $MNT " /proc/mounts 2>/dev/null && umount "$MNT" 2>/dev/null
+	[ -n "${TMNT:-}" ] && umount /mnt 2>/dev/null
+	return 0
+}
+trap cleanup EXIT
+
+[ "$(id -u)" -eq 0 ] || die "please run as root"
+
+for t in fdisk mkfs.ext4 mkswap grub-install; do
+	command -v "$t" >/dev/null 2>&1 || die "required tool '$t' not found"
+done
+
+banner() {
+	clear 2>/dev/null
+	msg ""
+	msg "  ============================================================"
+	msg "    Mentalnet GNU/Linux - hard disk installer"
+	msg "  ============================================================"
+	msg ""
+	msg "  This will copy the live system from the CD onto a local"
+	msg "  disk, install the GRUB bootloader, and make the disk"
+	msg "  bootable on its own."
+	msg ""
+}
+
+list_disks() {
+	for d in /sys/block/*; do
+		dev=${d##*/}
+		case "$dev" in
+			sr*|loop*|ram*|zram*|md*|dm-*|fd*|nbd*) continue ;;
+		esac
+		size=$(cat "$d/size" 2>/dev/null) || continue
+		mib=$((size / 2048))
+		model=$(cat "$d/device/model" 2>/dev/null | tr -d ' ')
+		printf '    /dev/%-6s %6s MiB   %s\n' "$dev" "$mib" "${model:-}"
+	done
+}
+
+banner
+msg "  Detected disks:"
+list_disks
+msg ""
+
+printf '  Disk to install to (e.g. sda): '
+read -r DISK
+[ -n "${DISK:-}" ] || die "no disk given"
+case "$DISK" in
+	sr*|loop*|ram*|zram*|md*|dm-*|fd*|nbd*) die "refusing to use $DISK" ;;
+	*[!/a-z0-9]*) die "invalid disk name" ;;
+esac
+DEV="/dev/$DISK"
+SYS="/sys/block/$DISK"
+[ -d "$SYS" ] && [ -b "$DEV" ] || die "$DEV is not a block device"
+
+SIZE=$(cat "$SYS/size")
+[ "$SIZE" -ge "$MIN_DISK_SECTORS" ] \
+	|| die "$DEV is too small (need $((MIN_DISK_SECTORS / 2048)) MiB minimum)"
+
+if grep -q "^$DEV" /proc/mounts; then
+	die "$DEV (or a partition on it) is currently mounted"
+fi
+
+msg ""
+warn "ALL DATA on $DEV will be DESTROYED without further notice."
+printf '  Type YES to continue: '
+read -r ANSWER
+[ "${ANSWER:-}" = "YES" ] || { msg "Aborted."; exit 0; }
+
+# --- swap? ---------------------------------------------------------------
+printf '  Create a swap partition? [y/N]: '
+read -r SWAPANS
+SWAP=0
+case "${SWAPANS:-}" in
+	y|Y|yes|Yes|YES) SWAP=1 ;;
+esac
+
+SWAP_SECTORS=0
+if [ "$SWAP" -eq 1 ]; then
+	MEM_KB=$(awk '/^MemTotal:/{print $2}' /proc/meminfo)
+	SWAP_MIB=$((MEM_KB / 1024 * 2))
+	[ "$SWAP_MIB" -gt 512 ] && SWAP_MIB=512
+	[ "$SWAP_MIB" -lt 32 ] && SWAP_MIB=32
+	SWAP_SECTORS=$((SWAP_MIB * 2048))
+	msg "  Swap partition: ${SWAP_MIB} MiB"
+fi
+
+# --- partition -----------------------------------------------------------
+msg "  Partitioning $DEV (MBR, root at sector $BOOT_START_SECTORS) ..."
+
+if [ "$SWAP" -eq 1 ]; then
+	P1_END=$((SIZE - SWAP_SECTORS - 1))
+	P2_START=$((SIZE - SWAP_SECTORS))
+	printf 'o\nn\np\n1\n%d\n%d\nn\np\n2\n%d\n%d\nt\n2\n82\na\n1\nw\n' \
+		"$BOOT_START_SECTORS" "$P1_END" \
+		"$P2_START" "$((SIZE - 1))" \
+	| fdisk -u "$DEV" >/dev/null || die "fdisk failed"
+else
+	printf 'o\nn\np\n1\n%d\n%d\na\nw\n' \
+		"$BOOT_START_SECTORS" "$((SIZE - 1))" \
+	| fdisk -u "$DEV" >/dev/null || die "fdisk failed"
+fi
+
+ROOTPART="${DEV}1"
+i=0
+while [ ! -b "$ROOTPART" ] && [ "$i" -lt 10 ]; do
+	i=$((i + 1))
+	partprobe "$DEV" 2>/dev/null
+	sleep 1
+done
+[ -b "$ROOTPART" ] || die "$ROOTPART did not appear after partitioning"
+
+# --- filesystems ---------------------------------------------------------
+msg "  Creating ext4 filesystem on $ROOTPART ..."
+mkfs.ext4 -F -L rootfs "$ROOTPART" >/dev/null || die "mkfs.ext4 failed"
+
+if [ "$SWAP" -eq 1 ]; then
+	msg "  Creating swap on ${DEV}2 ..."
+	mkswap "${DEV}2" >/dev/null || die "mkswap failed"
+fi
+
+# --- copy the live system ------------------------------------------------
+# /mnt lives on the read-only CD, so put a writable tmpfs over it to
+# get a usable mount point
+TMNT=
+if ! grep -q ' /mnt ' /proc/mounts; then
+	mount -t tmpfs -o mode=0755 tmpfs /mnt || die "cannot set up /mnt"
+	TMNT=1
+fi
+mkdir -p "$MNT"
+mount -t ext4 "$ROOTPART" "$MNT" || die "could not mount $ROOTPART"
+
+msg "  Copying the system (this takes a while) ..."
+
+# NOTE: one single tar invocation per side. busybox tar stops reading at
+# the first end-of-archive marker, so piping several archives through
+# '-' would silently transfer only the first directory.
+DIRS=
+for d in bin boot etc home lib lib32 lib64 media opt root sbin srv usr var; do
+	[ -e "/$d" ] && DIRS="$DIRS $d"
+done
+(cd / && tar -cf - $DIRS) | (cd "$MNT" && tar -xpf -) \
+	|| die "copying failed"
+
+# mount points that live in tmpfs on the CD
+mkdir -p "$MNT/proc" "$MNT/sys" "$MNT/dev" "$MNT/tmp" "$MNT/run" "$MNT/mnt"
+
+# CD-only artifacts must not end up on the disk
+rm -f "$MNT/boot/grub/grub-eltorito.img"
+
+# --- /etc/fstab ----------------------------------------------------------
+msg "  Writing /etc/fstab ..."
+cat > "$MNT/etc/fstab" <<EOF
+# /etc/fstab - generated by mentalnet-install
+$ROOTPART / ext4 rw,noatime 0 1
+proc /proc proc defaults 0 0
+devpts /dev/pts devpts defaults,gid=5,mode=620,ptmxmode=0666 0 0
+tmpfs /dev/shm tmpfs mode=1777 0 0
+tmpfs /tmp tmpfs mode=1777 0 0
+tmpfs /run tmpfs mode=0755,nosuid,nodev 0 0
+sysfs /sys sysfs defaults 0 0
+EOF
+if [ "$SWAP" -eq 1 ]; then
+	printf '%s none swap sw 0 0\n' "${DEV}2" >> "$MNT/etc/fstab"
+fi
+
+# --- bootloader ----------------------------------------------------------
+msg "  Writing bootloader configuration ..."
+sed "s|@ROOTDEV@|$ROOTPART|" /usr/share/mentalnet/grub-disk.cfg \
+	> "$MNT/boot/grub/grub.cfg" \
+	|| die "could not write grub.cfg"
+
+msg "  Installing GRUB to the MBR of $DEV ..."
+grub-install --boot-directory="$MNT/boot" "$DEV" >/dev/null 2>&1 \
+	|| die "grub-install failed"
+
+sync
+umount "$MNT" || umount -f "$MNT" || die "could not unmount $MNT"
+[ -n "$TMNT" ] && umount /mnt
+
+msg ""
+msg "  ============================================================"
+msg "    Installation complete!"
+msg "  ============================================================"
+msg ""
+msg "  Root partition : $ROOTPART (ext4)"
+[ "$SWAP" -eq 1 ] && msg "  Swap           : ${DEV}2 (${SWAP_MIB} MiB)"
+msg "  Login          : root / mnlinux"
+msg ""
+msg "  Remove the CD and reboot:   poweroff"
+msg ""

board/mentalnet/overlay/usr/share/mentalnet/grub-disk.cfg

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+set default="0"
+set timeout="5"
+
+menuentry "Mentalnet GNU/Linux" {
+    linux /boot/bzImage root=@ROOTDEV@ rootwait rw console=ttyS0,9600n8 console=tty0
+}