feat: add ephvm related scripts

justfile

@@ -33,6 +33,18 @@ build:
 iso:
     nixos-rebuild build-image --image-variant iso-installer --flake .#iso
 
+# build ephemeral VM image
+ephvm-build:
+    nixos-rebuild build-image --image-variant qemu --flake .#ephvm
+
+# run ephemeral VM
+ephvm-run *ARGS:
+    bash scripts/ephvm-run.sh $(find -L result -name '*.qcow2' | head -1) {{ARGS}}
+
+# ssh into running ephemeral VM
+ephvm-ssh port="2222":
+    ssh -p {{port}} -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null matej@localhost
+
 # garbage collect old generations
 clean:
     sudo nix-collect-garbage $(nix eval --raw -f ./nix.nix nix.gc.options)

scripts/ephvm-run.sh

@@ -0,0 +1,87 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SSH_PORT=2222
+MEMORY=8G
+CPUS=4
+MOUNTS=()
+CLAUDE_DIR=""
+CLAUDE_JSON=""
+IMAGE=""
+
+usage() {
+  cat <<EOF
+Usage: ephvm-run.sh <image.qcow2> [options]
+
+Options:
+  --mount <path>       Mount host directory into VM (repeatable)
+  --claude <path>      Mount claude config dir writable into VM
+  --claude-json <path> Copy claude.json into mounted claude dir
+  --memory <size>      VM memory (default: 8G)
+  --cpus <n>         VM CPUs (default: 4)
+  --ssh-port <port>  SSH port forward (default: 2222)
+EOF
+  exit 1
+}
+
+[ "${1:-}" ] || usage
+
+IMAGE="$1"
+shift
+
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --mount)      MOUNTS+=("$2"); shift 2 ;;
+    --claude)     CLAUDE_DIR="$2"; shift 2 ;;
+    --claude-json) CLAUDE_JSON="$2"; shift 2 ;;
+    --memory)     MEMORY="$2"; shift 2 ;;
+    --cpus)     CPUS="$2"; shift 2 ;;
+    --ssh-port) SSH_PORT="$2"; shift 2 ;;
+    *)          echo "unknown option: $1"; usage ;;
+  esac
+done
+
+if [ ! -f "$IMAGE" ]; then
+  echo "error: image not found: $IMAGE"
+  exit 1
+fi
+
+ACCEL="tcg"
+[ -r /dev/kvm ] && ACCEL="kvm"
+
+QEMU_ARGS=(
+  qemu-system-x86_64
+  -accel "$ACCEL"
+  -m "$MEMORY"
+  -smp "$CPUS"
+  -drive "file=$IMAGE,format=qcow2,snapshot=on"
+  -nic "user,hostfwd=tcp::${SSH_PORT}-:22"
+  -nographic
+)
+
+if [ "$ACCEL" != "tcg" ]; then
+  QEMU_ARGS+=(-cpu host)
+fi
+
+FS_ID=0
+for mount_path in "${MOUNTS[@]}"; do
+  mount_path=$(realpath "$mount_path")
+  name=$(basename "$mount_path")
+  QEMU_ARGS+=(
+    -virtfs "local,path=$mount_path,mount_tag=mount_$name,security_model=none,id=fs${FS_ID}"
+  )
+  FS_ID=$((FS_ID + 1))
+done
+
+if [ -n "$CLAUDE_DIR" ]; then
+  CLAUDE_DIR=$(realpath "$CLAUDE_DIR")
+  QEMU_ARGS+=(
+    -virtfs "local,path=$CLAUDE_DIR,mount_tag=claude,security_model=none,id=fs${FS_ID}"
+  )
+fi
+
+if [ -n "$CLAUDE_JSON" ]; then
+  QEMU_ARGS+=(-fw_cfg "name=opt/claude.json,file=$CLAUDE_JSON")
+fi
+
+exec "${QEMU_ARGS[@]}"