Running Emacs in microVM

# ----------------------------------------------------------
# NetBSD development shell with Emacs included.
# Time-stamp: <Last changed 2026-09-19 16:59:22 by magnolia>
# ----------------------------------------------------------

# Disable: unusual "FROM" naming, multiple RUN don't matter, and non-JSON CMD
# hadolint global ignore=DL3006,DL3025,DL3059

# `base' -- The core system. Contains the essential binaries, shared libraries,
# and utilities required for a minimally functional NetBSD system.
# This set is mandatory.

# `etc' -- System configuration files (primarily under /etc and a few other places).
# Needed for a complete install from scratch;
# provides the default configuration skeleton.

# `comp' -- Compiler/toolchain set. Includes compilers (C/C++),
# header files (/usr/include), static libraries, linker, make,
# and related development tools.

FROM base,etc,comp

# Mandatory -- a name of the service
LABEL smolbsd.service="devsh"

# Shrink the final image to only needed content + extra NNN MB
LABEL smolbsd.minimize=+512
# Extra packages
LABEL smolbsd.addpkgs="pkgin pkg_tarup pkg_install sqlite3 rsync curl"
# Microvm will use a `pty' as console
LABEL smolbsd.use_pty="y"
# 2G disk initially; it will be truncated to minimum + extra NNN MB
LABEL smolbsd.imgsize=2048

ARG HOSTNAME=bsd
ARG USERSHELL=/bin/ksh
ENV USERNAME=magnolia

# Note: INCLUDE is SMOLerfile extension!
# For interactive shell; provided by smolBSD distribution.
INCLUDE smolerfiles/usershell.inc

# ====================================
#               EMACS
# ====================================

# Create ~/.emacs with minimal tuning.
RUN <<EOF
cat > ${HOMEDIR}/.emacs << 'EMACS'
;;; Minimal Emacs config for NetBSD
;; Basic settings
(setq
  column-number-mode t
  ring-bell-function 'ignore
  scroll-step 1
  scroll-conservatively 100000
  scroll-preserve-screen-position 1
  scroll-margin 0
  mouse-wheel-scroll-amount '(1)
  mouse-wheel-progressive-speed nil
  global-visual-line-mode nil
  show-paren-mode t
  tab-always-indent 'indent
  tab-width 4
  tool-bar-mode nil
  truncate-lines nil
  word-wrap t
  make-backup-files nil
  auto-save-default nil
)

;; No line numbers (can be toggled by "C-c l")
(global-display-line-numbers-mode -1)

(setq-default indent-tabs-mode nil)
(global-hl-line-mode 1)
(delete-selection-mode t)
(desktop-save-mode 1)
(savehist-mode 1)

;; No menu
(menu-bar-mode -1)

;; Killing the current Dired buffer upon navigating into a different directory.
(setq dired-kill-when-opening-new-dired-buffer t)

;; Basic C settings
(setq c-default-style "stroustrup")
(setq c-basic-indent 4)
(setq c-basic-offset 4)
(c-set-offset 'innamespace 0)
(c-set-offset 'inextern-lang 0)

;; Some useful keybindings
(define-key global-map (kbd "RET") #'newline-and-indent)
(global-set-key (kbd "M-o") #'other-window)
(global-set-key (kbd "M-a") #'beginning-of-line) ; QEMU intercepts "C-a"
(global-set-key (kbd "M-e") #'end-of-line) ; For consistency
(global-set-key (kbd "C-c l") #'display-line-numbers-mode)
EMACS
chown ${USERNAME} ${HOMEDIR}/.emacs
chmod 600 ${HOMEDIR}/.emacs
EOF

# To use Emacs keys in the shell
RUN echo 'set -o emacs' > /etc/shrc

RUN echo 'alias ll="ls -la"' >> /etc/shrc

# Install Emacs
RUN pkgin up && pkgin -y in emacs-nox11

# Install GNU make; we will use it instead of default `bsdmake'
RUN pkgin -y in gmake

# Login to `ksh', the default shell on NetBSD
CMD login -f -p $USERNAME

#!/bin/bash

# `smolbsd-build.sh SERVICE'
# ==========================

# NETBSD_ROOT envvar should point to the smolBSD directory on the host.
if [ -z "$NETBSD_ROOT" ]; then
    echo "Error: NETBSD_ROOT envvar not defined."
    exit 2
fi

if [ -z "$1" ]; then
    echo "Usage: smolbsd-build.sh SERVICE"
    exit 1
fi

pushd .
IMAGE="smolerfiles/Dockerfile.$1"
cd $NETBSD_ROOT
echo "Building $IMAGE ..."
./smoler.sh build $IMAGE
popd

#!/bin/bash

# `smolbsd-run.sh SERVICE'
# ========================

# NETBSD_ROOT envvar should point to the smolBSD directory on the host.
if [ -z "$NETBSD_ROOT" ]; then
    echo "Error: NETBSD_ROOT envvar not defined."
    exit 2
fi

if [ -z "$1" ]; then
    echo "Usage: smolbsd-run.sh SERVICE"
    exit 1
fi

pushd .
cd $NETBSD_ROOT
# 1) -f CONFIG      VM configuration file; it's created automatically during the build stage.
# 2) -P             use PTY terminal
# 3) -n 2           enable stopping VM from ksh (as `su'): . /etc/include/shutdown
# 4) -w PATH        mount host's PATH to guest's /mnt/
./startnb.sh -f "etc/$1.conf" -P -n 2 -w ${HOME}/workspace/devel
popd