MegaZeux Development VMs

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Revision as of 01:56, 28 October 2024 by Lachesis (talk | contribs) (→‎Graphical environment: Mention config, wmenu in Debian 13; move dmenu block here.)
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This page contains VM images for testing MegaZeux (and potentially other software) for non-x86 architectures via QEMU. Each image contains a cloned copy of the MegaZeux Git repository, all tools required to build a local copy of MegaZeux, and a minimalist window environment (i3 in Debian or CTWM in NetBSD) to run MegaZeux in.

The login for all VMs is mzx with the password mzx. The MegaZeux Git repository is located at ~/megazeux (or /megazeux in older images).

This page is currently a work-in-progress. Because of this, they are behind a password; ask Lachesis for it on Discord.

Linux/BSD

  • "Main" architectures usually correspond to existing or future MegaZeux ports and are fairly well-supported by Linux and/or BSD distributions. Linux and BSD ports are omitted from the table for obvious reasons. RISC-V is included in this group, as it is an increasingly relevant Linux (and eventually Android) target.
  • "Secondary" architectures do not correspond to existing or future MegaZeux ports, and (with the exception of m68k) are/were primarily used for business servers and workstations. While it's unlikely that MegaZeux will be run natively on most of these platforms, testing on these platforms improves MegaZeux's portability.

Build times provided were observed using an i7-7700 running QEMU from a hypervisor guest, and are mainly intended to give a sense of scale. These may vary significantly depending on your machine and setup. For platforms where --enable-kvm is relevant, it was not used.

The current head in ~/megazeux should be the most recent head a full build was tested with.

x86/ARM and other Alpine architectures

This group includes the most common architectures that MegaZeux is run on, x86 and ARM. Secondary architectures that Alpine Linux provides install media for are also included for convenience (ppc64le and s390x). Aside from ARMel, all of these images are Alpine Linux based.

The RISC-V RV64GC and LoongArch64 architectures will probably move to this group in the future.

Architecture Related Ports Distribution Options make
unit
testworlds 		Fails Other Issues Image Links
x86
qemu-system-i386 8.2.7
  • Windows
  • Mac OS X
  • Android
 Alpine Linux 3.20 
-m 2048 -smp 4
-hda [...]
4m20s (-j4)
2m11s (-j4)
32s 		— — 243MiB
x86_64
qemu-system-x86_64 8.2.7
  • Windows
  • macOS
  • Android
 Alpine Linux 3.20 
-m 2048 -smp 4
-hda [...]
2m59s (-j4)
1m31s (-j4)
21s 		— — 288MiB
ARMel
qemu-system-arm 5.2.0
  • Nintendo DS
  • Nintendo 3DS
  • Raspberry Pi
  • GP2X
 Debian Unstable[1] 
-M versatilepb -m 256M -cpu arm1176
-kernel [...] -dtb [...] -append "root=/dev/sda1 panic=10"
-hda [...]
-no-reboot
9m24s
2m44s
27s 		— Testing MZX should be done in system emulation, as several vio tests and the test worlds fail with chroot.sh due to a QEMU bug. The red and blue video components are reversed. 340MiB QEMU Raspberry Pi kernels and scripts.
ARMv7
qemu-system-arm 8.2.7
  • Android
  • Raspberry Pi
  • PlayStation Vita
  • Pandora
 Alpine Linux 3.20 
-M virt -m 2048 -cpu cortex-a15 -smp 4
-kernel [...] -initrd [...] -append "root=/dev/vda3 rootfstype=ext4"
-hda [...] -boot c
-netdev user,id=eth0
-device virtio-net-device,netdev=eth0
-device virtio-gpu
-usb -device usb-ehci,id=ehci
-device usb-mouse,bus=ehci.0
-device usb-kbd,bus=ehci.0
3m40s (-j4)
2m34s (-j4)
34s 		— SMP makes boot very slow for some reason. For faster boot (but slower compilation), disable it.
Alpine armv7 is equivalent to Debian armhf. 		243MiB See ARM64.
ARM64
qemu-system-aarch64 8.2.7
  • macOS
  • Android
  • Raspberry Pi
  • Nintendo Switch
 Alpine Linux 3.20 
-M virt -m 2048 -cpu cortex-a72 -smp 4
-kernel [...] -initrd [...] -append "root=/dev/vda3 rootfstype=ext4"
-hda [...] -boot c
-netdev user,id=eth0
-device virtio-net-device,netdev=eth0
-device VGA
-usb -device usb-ehci,id=ehci
-device usb-mouse,bus=ehci.0
-device usb-kbd,bus=ehci.0
4m01s (-j4)
1m54s (-j4)
28s 		— — 286MiB Debian Wiki (archived)

Blog post with more detailed info. (archived)
Both of these are outdated; the BIOS image seems to be included out of the box in newer QEMU versions.

PowerPC 64 LE
qemu-system-ppc64 8.2.7 		— Alpine Linux 3.20 
-M pseries-8.2 -m 2048 -smp 4,sockets=4,cores=1,threads=1
-hda [...]
-device virtio-net-pci,netdev=net0
-netdev user,id=net0
2m09s (-j4)
1m20s (-j4)
22s 		— Video freezes mid-boot, so adding -nographic may be preferable. 257MiB
s390x (IBM Z)
qemu-system-s390x 8.2.7 		— Alpine Linux 3.20 
-M s390-ccw-virtio -m 4096 -smp 4
-hda [...]
-device virtio-net-pci
-nographic
FIXME (-j4)
FIXME (-j4)
FIXME 		— No video.
This emulator seems very fragile for some systems/environments. 		235MiB

Other main architectures

This group contains all other "main" architectures. Debian is used for these images.

Architecture Related Ports Distribution Options make
unit
testworlds 		Fails Other Issues Image Links
MIPSeb
qemu-system-mips 8.2.7 		— Debian 10.13 
-M malta -m 256
-kernel [...] -initrd [...]
-append "root=/dev/sda1"
-drive [...]
-device usb-mouse -device usb-kbd
-vga std
45m49s
37m22s
1m20s 		— Use chroot.sh for compilation.
Likely the last image for this architecture, as Debian discontinued it. 		373MiB Setup (archived)
MIPSel
qemu-system-mipsel 8.2.7
  • PlayStation Portable
 Debian 12.7 
-M malta -m 256
-kernel [...] -initrd [...]
-append "root=/dev/sda1"
-device usb-mouse -device usb-kbd
-vga std
76m04s
45m08s
1m26s 		— Use chroot.sh for compilation. 420MiB Setup (archived)
MIPS64el
qemu-system-mips64el 8.2.7 		— Debian 12.7 
-M malta -m 2048 -cpu 5KEc
-kernel [...] -initrd [...]
-append "root=/dev/sda1"
-device usb-mouse -device usb-kbd
-vga std
111m53s
149m38s
53s 		— Use chroot.sh for compilation. 421MiB Setup (archived)

More info (archived)

PowerPC
qemu-system-ppc 6.0.0
  • Mac OS X
  • Nintendo Wii
  • Nintendo Wii U
 Debian Unstable 10.0[2] 
-L pc-bios -boot c
-M mac99,via=pmu -m 1G
-prom-env "boot-device=hd:,\yaboot"
-prom-env "boot-args=conf=hd:,\yaboot.conf"
-drive [...]
-serial stdio
-g 1024x768x32
4m50s
1m26s
17s 		— — 459MiB QEMU Wiki (archived)
PowerPC 64
qemu-system-ppc64 6.0.0
  • Mac OS X
 Debian Unstable 10.0[3][4] 
-L pc-bios -boot c
-M mac99,via=pmu -m 2048 -cpu 970fx
-prom-env "boot-device=hd:,\yaboot"
-prom-env "boot-args=conf=hd:,\yaboot.conf"
-drive [...]
-serial stdio
-g 1024x768x32
3m36s
59s
14s 		— — 483MiB QEMU Wiki (archived)
RISC-V RV64GC
qemu-system-riscv64 8.2.7 		— Debian Unstable[5] 
-M virt -smp 4 -m 2048M
-kernel uboot.elf
-append "console=ttyS0 rw root=/dev/vda1"
-object rng-random,filename=/dev/urandom,id=rng0
-device virtio-rng-device,rng=rng0
-device virtio-blk-device,drive=hd0
-drive file=[...],format=qcow2,id=hd0
-device virtio-net-device,netdev=usernet
-netdev user,id=usernet,hostfwd=tcp::22222-:22
-device VGA
-usb -device usb-ehci,id=ehci
-device usb-mouse,bus=ehci.0 -device usb-kbd,bus=ehci.0
3m36s (-j4)
2m59s (-j4)
32s 		— — 542MiB Debian Wiki RISC-V article (archived)
SuperH SH-4
qemu-sh4 8.2.7 (binfmt-misc)
  • Sega Dreamcast
 Debian Unstable[6] n/a 2m00s (-j4)
1m05s (-j4)
36s 		— Only works using user emulation right now; use chroot.sh. Since this VM does boot it might be an issue with newer kernels. 283MiB Building Debian VMs with debootstrap (archived)

Secondary architectures

These architectures do not correspond to any current MegaZeux ports. MegaZeux will probably never run on actual hardware several of these architectures.

Architecture Related Ports Distribution Options make
unit
testworlds 		Fails Other Issues Image Links
DEC Alpha
qemu-system-alpha 5.2.0 		— Debian Unstable 2021-04-17 
-m 2048
-kernel [...] -initrd [...]
-append "root=/dev/sda3 rw"
-drive [...]
-device VGA
4m15s
1m09s
14s 		— Use --disable-stack-protector. D-Bus and X11 currently do not work correctly due to alignment issues, so use run.serial.sh. 455MiB QEMU Wiki (archived)
Motorola 68000
qemu-system-m68k 5.2.0 		— Debian Unstable 2021-04-17 
-M q800 -m 1000M
-kernel [...] -initrd [...]
-append "root=/dev/sda1 rw console=ttyS0 console=tty"
-drive [...]
-net nic,model=dp83932 -net user
-g 800x600x16
4m34s
1m20s
20s 		— — 355MiB QEMU Wiki (archived)
PA-RISC
qemu-system-hppa 5.2.0 		— Debian Unstable 10.0[7] 
-m 2048 -accel tcg,thread=multi -smp 4
-drive [...]
-global artist.width=800
-global artist.height=600
-serial mon:stdio
34m51s (-j4)
13m02s (-j4)
1m51s 		— Use --disable-stack-protector. Emulation is SLOW! Video doesn't work yet; use run.serial.sh (see setup notes). 432MiB QEMU Wiki (archived)
PA-RISC Linux Wiki - QEMU (archived)
SPARC
qemu-system-sparc 6.0.0 		— NetBSD 9.2[8] 
-M SS-20
-m 512M
-drive [...]
-net nic -net user
5m50s
1m26s
25s
(a173946a) 		— Use --prefix /usr/pkg --disable-libsdl2. SDL2 works headless but can't find a texture format and is missing -Wl,-rpath. force_bpp=16 will match colors to the nearest indexed colors. May hang during IO operations, but so far this has only happened with pkgsrc. 358MiB QEMU Wiki (archived)
SPARC64
qemu-system-sparc64 6.0.0 		— NetBSD 9.2[9] 
-m 2048M
-drive [...]
-serial mon:stdio
14m50s
3m38s
33s
(a173946a) 		— Use --prefix /usr/pkg --disable-libsdl2. SDL2 works headless but can't find a texture format and is missing -Wl,-rpath. force_bpp=16 will match colors to the nearest indexed colors. 439MiB QEMU Wiki (archived)

Setup

If (for whatever reason) you want to set up your own VM images or a similarly configured machine, this is how the VM images above were generated.

Base image

Alpine Linux or Debian GNU/Linux are assumed in most of these steps, but they can be adapted to other distros. If one of the alternate setups is required, skip the installer steps in this section. NetBSD, which can be used for some architectures, is covered separately.

  1. Set up initial QEMU disk image. 
    qemu-img create -f qcow2 arch.debian10.qcow2 20G
  2. Extract installation media vmlinux/initrd from ISO (if needed) and set up initial install.sh script.
  3. Run installer. Leave root password blank, create user mzx with password mzx and sudo/doas access. Do not install a desktop environment.
  4. If needed, extract runtime vmlinux/vmlinuz/initrd from the virtual machine (required for ARM, MIPS, RISC-V, Alpha, m68k, and SH-4). The easiest way to do this is to use the guestfish utility from libguestfs. 
    guestfish --ro -a arch.debian10.qcow2 -i

    Then: 

    copy-out /boot/vmlinux-X.XX.X-X-ARCH .
copy-out /boot/initrd.img-X.XX.X-X-ARCH .
  5. Set up a shell script to run the VM with QEMU, if you haven't already. The older development VM images have separate run.serial.sh and run.sh scripts as needed, but it is now preferred to have one run.sh script that can run on serial when provided -nographic. This script should not use the option -enable-kvm by default; this should be provided by the user.

Environment setup

  1. Set up basic editing utils (these may be preinstalled): 
    # Debian
sudo apt install nano

    # Alpine
doas apk add nano
  2. Set up /bin/l (chmod +x). 
    #!/bin/sh

LC_COLLATE="C" \
ls -la --color=always --group-directories-first "$@"
  3. Enable the community repository in Alpine Linux by editing /etc/apk/repositories and uncommenting the community repository URL.
  4. Update packages. 
    # Debian
sudo apt update
sudo apt upgrade

    # Alpine
doas apk update
doas apk upgrade

Setup MegaZeux

  1. Install packages for the tools and dependencies required to build MegaZeux: 
    # Debian
sudo apt install build-essential gdb git zlib1g-dev libpng-dev libogg-dev libvorbis-dev libsdl2-dev

    # Alpine
doas apk add build-base gdb git zlib-dev libpng-dev libogg-dev libvorbis-dev sdl2-dev
  2. Set up MegaZeux repository: 
    cd ~
git clone https://github.com/AliceLR/megazeux
  3. Build MegaZeux and run the tests. Debug builds are used to measure the times in the table above, as release builds can be quite slow to make in these VMs. Video is not required for any of these steps. The times in the table above were measured without the -enable-kvm option. 
    ./config.sh --platform unix-devel --enable-fps [any other flags here]
time make [use -jX with -smp]
time make unittest [use -jX with -smp]
time testworlds/run.sh unix-devel

Packaging the VM image

If preparing a VM tarball, some steps should be taken to reduce the size of the image.

  1. From the guest OS, clear the apt package cache: 
    # Debian
sudo apt clean

    # Alpine
doas apk cache clean
  2. Using guestfish from the host OS, fill all unused space in the image with 0s. This will increase the size of the image to its maximum size. (This method seems to be faster than using the dd if=/dev/zero trick some places cite or using zerofree from a guest rescue disk.) 
    guestfish --rw -a arch.debian10.qcow2 -i

    zero-free-space /
  3. To shrink your working copy of the image, compact it using qemu-img (and then test it): 
    mv arch.debian10.qcow2 arch.debian10.old.qcow2
qemu-img convert -O qcow2 arch.debian10.old.qcow2 arch.debian10.qcow2
  4. Finally, generate a compressed tarball containing the image and scripts: 
    mkdir arch/
cp *.sh arch.debian10.qcow2 arch/
XZ_OPT="-9" tar -cJf vm-mzx-arch-debian-10.0.tar.xz arch/

# If you have several cores and don't mind using them all, this
# makes xz use parallel compression to speed things up.
# The resulting tarball may be significantly larger, though.
XZ_OPT="-T0 -9" tar -cJf vm-mzx-arch-debian-10.0.tar.xz arch/

Extra software

The following packages might be useful depending on the platform and setup:

  • Console utilities: 
    # Debian
sudo apt install dialog screen lm-sensors lynx

    # Alpine
doas apk add dialog screen lm-sensors lynx
  • Extra tools for building libxmp and xmp-cli from source. 
    # Debian
sudo apt install autoconf automake libtool pkgconf

    # Alpine
doas apk add autoconf automake libtool pkgconf
  • clang may be useful for its sanitizers and built-in fuzzer, but it is quite large. It is better to install this after preparing and archiving the initial VM image. 
    # Debian
sudo apt install clang clang-tools llvm

    # Alpine
doas apk add clang clang-tools llvm
  • If this machine or VM is going to be shelled into: 
    # Debian
sudo apt install openssh-server

    # Alpine (note: you can just set this up during setup-alpine)
doas apk add openssh-server
  • If memory compression is required: 
    # Debian
sudo apt install zram-tools

Graphical environment

  1. Debian only: block the installation of dmenu. This is an unnecessary application launcher that will be replaced by wmenu or rofi. This is done by: 
    echo '
Package: suckless-tools
Pin: origin *
Pin-Priority: -1
' | sudo tee /etc/apt/preferences.d/no_goosesteppers
  2. Sway is the preferred graphical environment for these virtual machines, as it is fairly lightweight and runs well in a VM. In some hardware cases it may be less buggy than X11 (encountered on AML-S905X-CC v1). For Alpine Linux, please follow their detailed setup guide for setting up eudev, seatd, and $XDG_RUNTIME_DIR. Do not use the setup-desktop script, as it will install unnecessary software such as Firefox which will bloat the image (remember, there are nearly 20 of these images). 
    # Debian
sudo apt install sway xwayland foot wmenu i3status fonts-dejavu

# wmenu is only present in Debian 13+. For Debian 12, use rofi instead:
sudo apt install rofi

    # Alpine
doas apk add sway xwayland foot wmenu swaylock swaylockd swaybg grim wl-clipboard i3status swayidle font-dejavu

# If using virtio-gpu:
doas apk add mesa-dri-gallium

    Copy the config file and edit it: 

    mkdir -p ~/.config/sway
cp /etc/sway/config ~/.config/sway/config
  3. An alternative is i3, which is X11 based. For Alpine Linux, please follow their detailed setup guide for setting up Xorg and dbus. 
    # Debian
sudo apt install xorg i3-wm i3lock i3status rofi rxvt-unicode fonts-dejavu

    # Alpine
doas apk add i3wm i3lock i3status rofi rxvt-unicode font-dejavu

    The config file will be installed to ~/.config/i3/config on the first run.

  4. You may need to preset various user roles to use a graphical desktop: 
    # Debian
sudo usermod -a -G video [user]
sudo usermod -a -G audio [user]
sudo usermod -a -G input [user]

    # Alpine
doas adduser [user] video
doas adduser [user] audio
doas adduser [user] input
  5. A launcher for i3 and/or Sway might be useful. By default, these installations use TDM, a lightweight terminal-based startx wrapper (which also supports Wayland), but this can be done in several ways.
    • Set up tdm: 
      cd ~
git clone https://github.com/dopsi/console-tdm
cd console-tdm

      # Debian
sudo apt install dialog
sudo make install

      # Alpine
doas apk add bash dialog
doas make install

      For each user that will be using tdm: 

      tdmctl init
# You can skip whichever of these window managers isn't present.
tdmctl add i3 /usr/bin/i3
tdmctl add sway /usr/bin/sway extra

      Place the following in .profile (Alpine) or .bashrc (Debian): 

      # Optional: Sway hardware cursors may not work in VirtualBox or QEMU.
# This seems to have been fixed for a while and can safely be omitted.
export WLR_NO_HARDWARE_CURSORS=1

# Enable tdm when starting on the first VT (Sway-only, from the Alpine wiki).
if [ -z "$WAYLAND_DISPLAY" ] && [ "$(tty)" = "/dev/tty1" ]; then
  (tdm --disable-long-names && clear) || true
fi

# Alternatively:
# Enable tdm when starting either of the first two VTs.
if [ -z "$DISPLAY" ] && [ -n "$XDG_VTNR" ] && [ "$XDG_VTNR" -le 2 ]; then
  (tdm --disable-long-names && clear) || true
fi

      X11 only: place this in .xinitrc to allow tdm to start the selected X desktop. 

      # i3 only: xrdb -merge "$HOME"/.Xresources
exec tdm --xstart
    • For a graphical login, xdm is tolerable in a VM and easy to set up: 
      # Debian
sudo apt install xdm

      # Alpine
doas apk add xdm
    • Alternatively, just use "startx" or "sway" manually. In the case of the former, .xinitrc needs to be preset: 
      xrdb -merge "$HOME"/.Xresources
exec i3
  6. X11 only: Debian makes xterm default instead of urxvt, so fix that: 
    sudo update-alternatives --config x-terminal-emulator

    Set up ~/.Xresources from here. This is required to make urxvt not look awful. 

    cd ~
wget https://www.digitalmzx.com/lachesis/.Xresources
  7. If applicable, update the run.sh script and make sure the VM can start up with graphics and run MegaZeux with the software renderer. This may take some trial and error to get right, which is why QEMU options that have worked in the past are provided in the above tables.

PowerPC/PPC64 (Debian Unstable)

Setting up working Debian Unstable builds for PowerPC/PPC64 currently requires a little bit of extra work.

1. ^^ An old image supporting Yaboot is currently required because all Debian Unstable PPC/PPC64 installers based on grub-ieee1275 have major installation issues (as of 2021-05-09). Skip setting up an apt repository, then add this to /etc/apt/sources.list, sudo apt update, and sudo apt dist-upgrade:
deb [trusted=yes] http://ftp.debian.org/debian-ports sid main

Install the following packages afterward to get the installation roughly equivalent to a standard install. 

sudo apt install wget curl ftp gnupg debian-keyring debian-archive-keyring

Remove the old kernel and some large dependencies pulled in by mailutils (not required for these VMs): 

sudo apt remove linux-image-4.16.0-1-*
sudo apt remove mailutils --purge
sudo apt autoremove --purge
2. ^ The version of Yaboot in older Debian Unstable PPC64 installers does not support ext4 (even though the equivalent PowerPC installer Yaboot does). Use manual partitioning instead of guided partitioning to create an ext2 /boot partition:
#1 Apple
#2 1.0 MB boot
#3 256.0 MB ext2 /boot
#4 (drive size - 2GB - 258MB) ext4 /
#5 2.0 GB swap

PA-RISC (Debian Unstable)

1. ^ The Debian Installer in newer installer images crashes prior to partitioning. Like PowerPC, an older image needs to be installed, followed by a dist-update and cleanup. Follow the PowerPC instructions above. Make sure you back up the installed image once you've verified that the installation worked. The upgrade process is slow and will involve trial and error.
2. Optional: upgrading systemd may cause the VM to get stuck in an endless boot loop while attempting to run systemd-timesyncd. It may be beneficial to place holds on the relevant systemd packages until after the initial update.
sudo apt-mark hold libpam-systemd
sudo apt-mark hold libsystemd0
sudo apt-mark hold systemd
sudo apt-mark hold systemd-sysv
sudo apt-mark hold systemd-timesyncd
3. If the sudo apt dist-upgrade fails because of libgcc-s4, do the following, then repeat the sudo apt dist-upgrade.
sudo apt install -o Dpkg::Options::="--force-overwrite" libgcc-s4
4. TODO: due to either Artist emulation bugs in QEMU or a lack of driver support in Linux, running this VM in graphical mode will result in the graphical terminal freezing at a certain point. The boot process will continue as usual and the VM can be used from the serial terminal in this situation. This Xorg config fragment can at least get X to successfully start, but the Artist window will still be frozen.
Section "Device"
 Identifier "Artist"
 Driver "fbdev"
 Option "ShadowFB" "off"
EndSection

Section "Screen"
 Identifier "Screen0"
 Device "Artist"
 DefaultDepth 8
 DefaultFbBpp 8
 SubSection "Display"
  Depth 8
  Modes "800x600_60.00"
 EndSubSection
EndSection

Setup (Debian via chroot)

For most QEMU architectures Debian supports, setting up a virtual machine image via a chroot and debootstrap is faster, less painful, and results in a smaller image. For architectures without debian-installer (or with a broken installer, which is often the case for the Ports project), it is necessary.

^^^ No Debian Installer image is available for this architecture and it must be set up manually.

Once this section is completed, it should be possible to follow the normal Linux setup guide without further modifications.

  1. Install debootstrap, qemu-user-static, and debian-ports-archive-keyring. If you aren't using Debian as a host, debian-ports-archive-keyring is available here.
  2. qemu-img create -f qcow2 [arch here].debian12.qcow2 16G
mkdir root/
  3. As root: 
    modprobe nbd
qemu-nbd -c /dev/nbd0 [arch here].debian12.qcow2
parted -s -a optimal -- /dev/nbd0 mklabel msdos mkpart primary ext4 1MiB -2GiB mkpart primary linux-swap -2GiB -0
mkfs -t ext4 -L root /dev/nbd0p1
mkswap -L swap /dev/nbd0p2
mount /dev/nbd0p1 root/

    Run debootstrap to create an initial user environment: 

    # For ARMel:
debootstrap --arch armel bookworm root/ https://ftp.debian.org/debian

# For MIPSel:
debootstrap --arch mipsel bookworm root/ https://ftp.debian.org/debian

# For MIPS64el:
debootstrap --arch mips64el bookworm root/ https://ftp.debian.org/debian

# For RISC-V:
debootstrap --arch riscv64 unstable root/ https://ftp.debian.org/debian

# For SH-4:
debootstrap --arch sh4 --keyring=/usr/share/keyrings/debian-ports-archive-keyring.gpg unstable root/ http://ftp.ports.debian.org/debian-ports

    Finally: 

    # If your host environment doesn't have binfmt_misc set up,
# now is the time to copy qemu-[arch]-static into root/bin/.
# If your host environment has binfmt_misc set up, no further
# action is required; the host kernel will be able to run guest
# executables in the chroot.

umount root/
qemu-nbd -d /dev/nbd0
  4. Set up chroot.sh based on this template. You need to edit PLATFORM_IMAGE (and PLATFORM_NBD, if you intend to chroot into multiple images simultaneously). 
    #!/bin/sh

echo "usage: sudo ./chroot.sh"
echo ""
echo "*** WARNING ***"
echo "This script is utter garbage and is not guaranteed to be portable."
echo "Use at your own risk. If your host doesn't have binfmt, copy the"
echo "appropriate qemu-user-static executable into the image /bin."
echo ""

[ "$(id -u)" = 0 ] || { echo "error: run as root or with sudo."; exit; }

PLATFORM_IMAGE=[FIXME YOUR ARCH HERE].debian12.qcow2
PLATFORM_NBD=/dev/nbd0
PLATFORM_PART="$PLATFORM_NBD"p1
PLATFORM_ROOT=root

mkdir -p "$PLATFORM_ROOT"

modprobe nbd || { echo "error: failed to initialized nbd module"; exit; }

if qemu-nbd -c "$PLATFORM_NBD" "$PLATFORM_IMAGE"; then
sleep 1
	if mount "$PLATFORM_PART" "$PLATFORM_ROOT"; then
		mount -o bind,ro /dev "$PLATFORM_ROOT"/dev
		mount -t proc none "$PLATFORM_ROOT"/proc
		mount -t sysfs none "$PLATFORM_ROOT"/sys

		chroot "$PLATFORM_ROOT" /bin/bash --login

		umount "$PLATFORM_ROOT"/dev "$PLATFORM_ROOT"/proc "$PLATFORM_ROOT"/sys "$PLATFORM_ROOT"
	else
		echo "error: failed to mount partition '$PLATFORM_PART' to '$PLATFORM_ROOT'"
	fi
	qemu-nbd -d "$PLATFORM_NBD"
else
	echo "error: failed to bind '$PLATFORM_IMAGE' to '$PLATFORM_NBD'"
fi
  5. Execute sudo ./chroot.sh to initialize qemu-nbd, mount the root partition to root/, and chroot into it. 
    # Verify machine name is armv7l (ARMel), mips (MIPSel), mips64 (MIPS64el), riscv64 (RISC-V), or sh4 (SH-4).
# Note that the kernel string will still contain the host architecture e.g. x86_64!
uname -a
  6. Edit /etc/fstab: 
    LABEL=swap none swap sw 0 0
LABEL=root / ext4 defaults 0 1

    Edit /etc/hostname: 

    [arch name here]

    Edit /etc/hosts and add at the beginning: 

    127.0.0.1    [arch name here]

    Create /etc/network/interfaces.d/eth0 (NOTE: for mipsel and mips64el, replace eth0 with enp0s11): 

    # This is the device name used by Debian and is needed for QEMU system emulation.
allow-hotplug eth0
iface eth0 inet dhcp

    Create /etc/network/interfaces.d/enp1s0: 

    # This allows networking to work from a chroot from Fedora.
allow-hotplug enp1s0
iface enp1s0 inet dhcp

    Create /etc/network/interfaces.d/lo: 

    # This configures the loopback interface.
# This breaks booting in ARMel and can be omitted for that platform.
auto lo
iface lo inet loopback
  7. Install and configure some required packages: 
    # If this architecture is from the Debian Ports project, this needs to be installed first.
# Officially supported architectures can ignore this step.
apt install debian-ports-archive-keyring

apt install sudo man-db locales console-setup wget curl ftp gnupg openntpd ntpdate

# These images generally use US/Mountain or America/Denver, depending on what is available.
dpkg-reconfigure tzdata

# Only select en_US.UTF-8 here; others can be added later if needed.
dpkg-reconfigure locales

# You may need to edit /etc/defaults/openntpd and add "-s" to the end of DAEMON_OPTS.

systemctl enable serial-getty@ttyS0.service
  8. Setup user: 
    adduser mzx
usermod -a -G sudo mzx
passwd -l root
  9. Set up a kernel and bootloader. This is different for each architecture.
    • ARMel: get a Raspberry Pi Linux kernel (4.19.50) and versatile-pb-buster.dtb here.
    • MIPSel: 
      apt install linux-image-4kc-malta

      Copy out the kernel and initrd from the image /boot directory into the VM directory. These will be provided as the arguments for -kernel and -initrd.

    • MIPS64el: 
      apt install linux-image-5kc-malta

      Copy out the kernel and initrd from the image /boot directory into the VM directory. These will be provided as the arguments for -kernel and -initrd.

    • RISC-V: 
      apt install linux-image-riscv64

# Also, some extra things to do here (see Debian Wiki RISC-V page):
apt install u-boot-menu u-boot-qemu
echo '
UBOOT_PARAMETERS="rw noquiet root=/dev/vda"
U_BOOT_FDT_DIR="noexist"' >> /etc/default/u-boot
u-boot-update

      Copy /usr/lib/u-boot/qemu-riscv64_smode/uboot.elf out of the image into the VM directory. This will serve as the argument to -kernel and is required to boot the virtual machine.

    • SH-4: 
      apt install linux-image-sh7751r

Setup (NetBSD)

^^ Setting up NetBSD is a little more involved than Debian. Note NetBSD also isn't aware of power management for some architectures and will use a full core while its VM is running.

  1. Set up initial QEMU disk image. 
    qemu-img create -f qcow2 arch.netbsd.qcow2 20G
  2. For whatever reason, the QEMU -kernel option doesn't seem to work with any BSD kernels, so right now any QEMU that requires -kernel should use a Linux instead.
  3. Run installer. Leave root password blank, create user mzx with password mzx and sudo access (if it doesn't give you the option, set the root password). Install all packages, including the X window system. Enable xdm and nptdate. If network autodetection doesn't work here (SPARC 32-bit), pkgin and pkgsrc will need to be set up manually after reboot. Otherwise, install both.
  4. Set up run.serial.sh script and run.
  5. As root, set up /bin/l: 
    echo '#!/bin/sh

LC_COLLATE="C" \
ls -la "$@"' > /bin/l
chmod a+x /bin/l
  6. As root, set a hostname, disable IPv6, enable DHCP (if it isn't already), and reboot: 
    # Set a hostname for this architecture e.g. SPARC, SPARC64, ARMv6.
echo "SPARC" > /etc/myname

# Disable IPv6 for DHCP.
# This prevents issues where all downloads can hang for a long time before
# the download starts (due to attempting IPv6 first and it timing out).
cp /etc/dhcpcd.conf ~/
echo '
# Disable IPv6 Support.
noipv6rs
noipv6' >> /etc/dhcpcd.conf

# If it wasn't enabled during install, you can enable DHCP like this.
cp /etc/rc.conf ~/
echo "dhcpcd=yes" >> /etc/rc.conf

# Reboot for these changes to take effect.
reboot
  7. If network wasn't available during installation, manually install pkgsrc. As root: 
    ftp http://ftp.netbsd.org/pub/pkgsrc/current/pkgsrc.tar.gz
tar -xzf pkgsrc.tar.gz -O /usr
chown root:wheel -R /usr/pkgsrc
  8. If network wasn't available during installation, manually install pkgin. As root: 
    # Replace ARCH and VERSION for the applicable architecture (e.g. sparc) and version (e.g. 9.2).
pkg_add http://cdn.netbsd.org/pub/pkgsrc/packages/NetBSD/ARCH/VERSION/All/pkgin
  9. As root, install packages with pkgin: 
    pkgin install sudo bash gmake git nano p7zip
pkgin install zlib png libogg libvorbis SDL SDL2
pkgin install lynx openssl ca-certificates

    If precompiled packages aren't available for this architecture, use pkgsrc to build and install these packages instead. WARNING: this will take a while.

  10. When configuring MegaZeux, make sure to use /usr/pkg as the prefix and to use gmake to invoke Makefile targets.
  11. Preparing the image is a little different from Debian, mainly since the Linux kernel does not have write support for NetBSD's filesystem by default. As root, clear the pkgin cache and zero free space. 
    pkgin clear
cat /dev/zero >delet_this
sync
rm delet_this

    If pkgsrc was used, make sure there are no work directories leftover in the pkgsrc tree (TODO).

    The image is now ready to be shrunk with qemu-img.

Links

1. NetBSD networking FAQ (archived).
2. NetBSD pkgsrc guide (archived).
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