Speed up offline ISO installs

bin/omarchy-iso-test

@@ -840,6 +840,11 @@ install_phase() {
   fi
   bootstrap_ssh
 
+  ssh_guest "echo $GUEST_PASSWORD | sudo -S cat /var/log/omarchy-install-timing.json 2>/dev/null" \
+    >"$RUN_DIR/omarchy-install-timing.json" 2>/dev/null || true
+  ssh_guest "echo $GUEST_PASSWORD | sudo -S cat /var/log/pacman.log 2>/dev/null" \
+    >"$RUN_DIR/pacman.log" 2>/dev/null || true
+
   log "Installed system is up. Saving base image."
   stop_vm
 }

configs/airootfs/usr/share/omarchy-iso/orchestrator/phases.py

@@ -65,6 +65,10 @@ def run(ctx: InstallContext, phases: list[tuple[str, PhaseFn]]) -> None:
     state["finished_at"] = time.time()
     _write_state(state_path, state)
 
+    timing_path = ctx.target / "var" / "log" / "omarchy-install-timing.json"
+    timing_path.parent.mkdir(parents=True, exist_ok=True)
+    _write_state(timing_path, state)
+
 
 def _write_state(path: Path, state: dict) -> None:
     # Dashboard polls this file while phases update it. Write atomically so the

configs/airootfs/usr/share/omarchy-iso/orchestrator/phases_impl.py

@@ -162,11 +162,13 @@ def _early_packages() -> list[str]:
 # ─────────────────────────────────────────────────────────────────────────────
 
 def prepare_live(ctx: InstallContext) -> None:
-    info("› initializing pacman keyrings")
+    # archiso's pacman-init.service initializes and populates every installed
-    subprocess.run(["pacman-key", "--init"], check=True)
+    # keyring before the live environment reaches multi-user.target. Pacstrap
-    subprocess.run(["pacman-key", "--populate", "archlinux"], check=True)
+    # then initializes the target's independent keyring, and archinstall does
-    subprocess.run(["pacman-key", "--populate", "omarchy"], check=True)
+    # its own repository sync before the first package transaction. Repeating
-    subprocess.run(["pacman", "-Sy", "--noconfirm"], check=True)
+    # both operations here only rebuilds trust databases and syncs twice.
+    info("› verifying live pacman initialization")
+    subprocess.run(["systemctl", "start", "pacman-init.service"], check=True)
 
     if ctx.is_protected:
         info("› protected mode: skipping whole-disk cleanup")
@@ -239,6 +241,7 @@ def arch_install_system(ctx: InstallContext) -> None:
         if config.mirror_config:
             installer.set_mirrors(mirror_handler, config.mirror_config, on_target=False)
 
+        _mount_offline_package_cache(ctx)
         _mask_mkinitcpio_pacman_hooks(ctx)
         try:
             info("› installing base system (mkinitcpio deferred to final Limine UKI build)")
@@ -274,6 +277,7 @@ def arch_install_system(ctx: InstallContext) -> None:
             installer.add_additional_packages(_runtime_package_list(ctx))
         finally:
             _unmask_mkinitcpio_pacman_hooks(ctx)
+            _unmount_offline_package_cache(ctx)
 
         # Standard arch finishers.
         if config.timezone:
@@ -575,6 +579,35 @@ def _install_early_packages(installer) -> None:
     installer.add_additional_packages(user_seed_packages)
 
 
+def _mount_offline_package_cache(ctx: InstallContext) -> None:
+    """Let pacstrap consume bundled packages without copying them first.
+
+    Pacstrap always points pacman's CacheDir inside the target. Without this
+    bind mount, pacman copies every package from the ISO's file:// repository
+    into that cache and then extracts it, duplicating several GiB of I/O.
+    Mount the already-populated offline repository at the target cache for the
+    duration of package installation. It is unmounted before genfstab so the
+    live-only bind can never leak into the installed system's fstab.
+    """
+    source = Path("/var/cache/omarchy/mirror/offline")
+    target = ctx.target / "var" / "cache" / "pacman" / "pkg"
+    if not source.is_dir():
+        raise RuntimeError(f"offline package cache missing: {source}")
+
+    target.mkdir(parents=True, exist_ok=True)
+    subprocess.run(["mount", "--bind", str(source), str(target)], check=True)
+    ctx.state.setdefault("bind_mounts", []).append(str(target))
+
+
+def _unmount_offline_package_cache(ctx: InstallContext) -> None:
+    target = str(ctx.target / "var" / "cache" / "pacman" / "pkg")
+    subprocess.run(["umount", target], check=True)
+    try:
+        ctx.state.get("bind_mounts", []).remove(target)
+    except ValueError:
+        pass
+
+
 def _is_devnull_symlink(path: Path) -> bool:
     try:
         return path.is_symlink() and path.readlink() == Path("/dev/null")

configs/profiledef.sh

@@ -12,7 +12,16 @@ bootmodes=('bios.syslinux' 'uefi.grub')
 arch="x86_64"
 pacman_conf="pacman-offline.conf"
 airootfs_image_type="squashfs"
-airootfs_image_tool_options=('-comp' 'xz' '-Xbcj' 'x86' '-b' '1M' '-Xdict-size' '1M')
+# Package archives in the offline mirror are already zstd-compressed. Storing
+# them in an outer XZ stream saves little space but makes pacman decompress XZ
+# while hashing and extracting every package during installation.
+airootfs_image_tool_options=(
+  '-comp' 'xz'
+  '-Xbcj' 'x86'
+  '-b' '1M'
+  '-Xdict-size' '1M'
+  '-action' 'uncompressed@subpathname(var/cache/omarchy/mirror/offline)'
+)
 bootstrap_tarball_compression=('zstd' '-c' '-T0' '--auto-threads=logical' '--long' '-19')
 file_permissions=(
   ["/etc/shadow"]="0:0:400"