diff --git a/script/qemu/README.base.md b/script/qemu/README.base.md
index 362c346..6353137 100644
--- a/script/qemu/README.base.md
+++ b/script/qemu/README.base.md
@@ -205,7 +205,10 @@ parameters and builds the command for you.
 - `--image-dir` — image cache directory (default `/var/lib/libvirt/images/iso`).
 - `--download-only` — download the image then exit (no VM).
 - `--name` — VM name (required for deployment).
-- `--memory`, `--vcpus`, `--disk-size` — VM sizing.
+- `--memory`, `--vcpus`, `--disk-size` — VM sizing. When omitted, `--memory`
+  and `--disk-size` default to the **minimum required by the chosen Ubuntu
+  version** (libosinfo values: 20.04 → 2048 MB/5G, 22.04 → 2048 MB/10G,
+  24.04+ → 3072 MB/20G); `--vcpus` defaults to 2.
 - `--ssh-key`, `--ask-password`, `--password-hash` — authentication.
 - `-y` / `--assume-yes` — auto-accept dependency installation.
 - `--no-install-deps` — never auto-install dependencies.
@@ -233,7 +236,10 @@ vous.
   `/var/lib/libvirt/images/iso`).
 - `--download-only` — télécharge l'image puis quitte (sans VM).
 - `--name` — nom de la VM (requis pour le déploiement).
-- `--memory`, `--vcpus`, `--disk-size` — dimensionnement de la VM.
+- `--memory`, `--vcpus`, `--disk-size` — dimensionnement de la VM. Omis,
+  `--memory` et `--disk-size` prennent le **minimum requis par la version
+  Ubuntu** choisie (valeurs libosinfo : 20.04 → 2048 Mo/5G, 22.04 →
+  2048 Mo/10G, 24.04+ → 3072 Mo/20G) ; `--vcpus` vaut 2 par défaut.
 - `--ssh-key`, `--ask-password`, `--password-hash` — authentification.
 - `-y` / `--assume-yes` — accepte automatiquement l'installation des
   dépendances.
diff --git a/script/qemu/README.fr.md b/script/qemu/README.fr.md
index c3788e9..dc6fd0d 100644
--- a/script/qemu/README.fr.md
+++ b/script/qemu/README.fr.md
@@ -120,7 +120,10 @@ vous.
   `/var/lib/libvirt/images/iso`).
 - `--download-only` — télécharge l'image puis quitte (sans VM).
 - `--name` — nom de la VM (requis pour le déploiement).
-- `--memory`, `--vcpus`, `--disk-size` — dimensionnement de la VM.
+- `--memory`, `--vcpus`, `--disk-size` — dimensionnement de la VM. Omis,
+  `--memory` et `--disk-size` prennent le **minimum requis par la version
+  Ubuntu** choisie (valeurs libosinfo : 20.04 → 2048 Mo/5G, 22.04 →
+  2048 Mo/10G, 24.04+ → 3072 Mo/20G) ; `--vcpus` vaut 2 par défaut.
 - `--ssh-key`, `--ask-password`, `--password-hash` — authentification.
 - `-y` / `--assume-yes` — accepte automatiquement l'installation des
   dépendances.
diff --git a/script/qemu/README.md b/script/qemu/README.md
index 206ad44..feb2ef7 100644
--- a/script/qemu/README.md
+++ b/script/qemu/README.md
@@ -112,7 +112,10 @@ parameters and builds the command for you.
 - `--image-dir` — image cache directory (default `/var/lib/libvirt/images/iso`).
 - `--download-only` — download the image then exit (no VM).
 - `--name` — VM name (required for deployment).
-- `--memory`, `--vcpus`, `--disk-size` — VM sizing.
+- `--memory`, `--vcpus`, `--disk-size` — VM sizing. When omitted, `--memory`
+  and `--disk-size` default to the **minimum required by the chosen Ubuntu
+  version** (libosinfo values: 20.04 → 2048 MB/5G, 22.04 → 2048 MB/10G,
+  24.04+ → 3072 MB/20G); `--vcpus` defaults to 2.
 - `--ssh-key`, `--ask-password`, `--password-hash` — authentication.
 - `-y` / `--assume-yes` — auto-accept dependency installation.
 - `--no-install-deps` — never auto-install dependencies.
diff --git a/script/qemu/deploy_qemu.py b/script/qemu/deploy_qemu.py
index a41f5eb..d4d167c 100755
--- a/script/qemu/deploy_qemu.py
+++ b/script/qemu/deploy_qemu.py
@@ -49,18 +49,22 @@ import urllib.request
 from pathlib import Path
 
 # --------------------------------------------------------------------------- #
-# Table des versions Ubuntu -> (nom de code, valeur --osinfo/libosinfo)
-# Le nom de code sert à construire l'URL de l'image cloud. Les valeurs LTS sont
-# stables ; --codename et --osinfo permettent de surcharger si la table vieillit.
+# Table des versions Ubuntu -> (nom de code, --osinfo, RAM min. Mo, disque min.)
+# Le nom de code sert à construire l'URL de l'image cloud. La RAM et le disque
+# minimaux proviennent de libosinfo (osinfo-db) : ce sont les seuils sous
+# lesquels virt-install émet un avertissement. Ils servent de valeurs PAR
+# DÉFAUT — une VM Ubuntu démarre avec ça sans gaspiller la RAM de l'hôte. Les
+# valeurs LTS sont stables ; --codename et --osinfo surchargent si la table
+# vieillit ; --memory / --disk-size surchargent le dimensionnement.
 # --------------------------------------------------------------------------- #
-UBUNTU_VERSIONS: dict[str, tuple[str, str]] = {
-    "20.04": ("focal", "ubuntu20.04"),
-    "22.04": ("jammy", "ubuntu22.04"),
-    "24.04": ("noble", "ubuntu24.04"),
-    "24.10": ("oracular", "ubuntu24.10"),
-    "25.04": ("plucky", "ubuntu25.04"),
-    "25.10": ("questing", "ubuntu25.10"),
-    # "26.04": ("resolute", "ubuntu26.04"),
+UBUNTU_VERSIONS: dict[str, tuple[str, str, int, str]] = {
+    "20.04": ("focal", "ubuntu20.04", 2048, "5G"),
+    "22.04": ("jammy", "ubuntu22.04", 2048, "10G"),
+    "24.04": ("noble", "ubuntu24.04", 3072, "20G"),
+    "24.10": ("oracular", "ubuntu24.10", 3072, "20G"),
+    "25.04": ("plucky", "ubuntu25.04", 3072, "20G"),
+    "25.10": ("questing", "ubuntu25.10", 3072, "20G"),
+    # "26.04": ("resolute", "ubuntu26.04", 3072, "20G"),
 }
 
 CLOUD_IMG_BASE = "https://cloud-images.ubuntu.com"
@@ -682,8 +686,9 @@ def ssh_command(user: str, ip: str, has_key: bool) -> str:
 # --------------------------------------------------------------------------- #
 def build_parser() -> argparse.ArgumentParser:
     versions_help = "\n".join(
-        f"    {v:<7} {code:<10} {image_url(code, 'amd64')}"
-        for v, (code, _osinfo) in UBUNTU_VERSIONS.items()
+        f"    {v:<7} {code:<10} RAM≥{ram:<5}Mo disque≥{disk:<4} "
+        f"{image_url(code, 'amd64')}"
+        for v, (code, _osinfo, ram, disk) in UBUNTU_VERSIONS.items()
     )
     p = argparse.ArgumentParser(
         formatter_class=argparse.RawDescriptionHelpFormatter,
@@ -739,15 +744,20 @@ def build_parser() -> argparse.ArgumentParser:
         "--hostname", help="Nom d'hôte interne (défaut : --name)."
     )
     g_vm.add_argument(
-        "--memory", type=int, default=8192, help="RAM en Mo (défaut : 8192)."
+        "--memory",
+        type=int,
+        default=None,
+        help="RAM en Mo (défaut : minimum requis par la version Ubuntu, "
+        "voir la liste ci-dessous).",
     )
     g_vm.add_argument(
-        "--vcpus", type=int, default=4, help="Nombre de vCPU (défaut : 4)."
+        "--vcpus", type=int, default=2, help="Nombre de vCPU (défaut : 2)."
     )
     g_vm.add_argument(
         "--disk-size",
-        default="20G",
-        help="Taille du disque virtuel, ex. 120G (défaut : 20G).",
+        default=None,
+        help="Taille du disque virtuel, ex. 120G (défaut : minimum requis "
+        "par la version Ubuntu, voir la liste ci-dessous).",
     )
     g_vm.add_argument(
         "--disk-dir",
@@ -907,10 +917,15 @@ def load_ssh_keys(paths: list[str]) -> list[str]:
 def main() -> None:
     args = build_parser().parse_args()
 
-    codename, default_osinfo = UBUNTU_VERSIONS[args.version]
+    codename, default_osinfo, min_ram, min_disk = UBUNTU_VERSIONS[args.version]
     if args.codename:
         codename = args.codename
     osinfo = args.osinfo or default_osinfo
+    # Dimensionnement par défaut = minimum requis par la version (libosinfo).
+    if args.memory is None:
+        args.memory = min_ram
+    if args.disk_size is None:
+        args.disk_size = min_disk
     url = image_url(codename, args.arch)
 
     # Chemin de l'image : déduit automatiquement si non fourni.
diff --git a/script/todo/todo.py b/script/todo/todo.py
index e467485..e01df23 100755
--- a/script/todo/todo.py
+++ b/script/todo/todo.py
@@ -812,9 +812,11 @@ class TODO:
             print(t("VM name is required!"))
             return
         version = self._qemu_prompt_version()
-        memory = input(t("RAM in MB (default: 8192): ")).strip() or "8192"
-        vcpus = input(t("vCPUs (default: 4): ")).strip() or "4"
-        disk_size = input(t("Disk size (default: 20G): ")).strip() or "20G"
+        # Laisser vide => le script applique le minimum requis par la version
+        # Ubuntu choisie (libosinfo). On n'envoie alors pas le flag.
+        memory = input(t("RAM in MB (blank = version minimum): ")).strip()
+        vcpus = input(t("vCPUs (default: 2): ")).strip()
+        disk_size = input(t("Disk size (blank = version minimum): ")).strip()
 
         default_key = self._qemu_default_ssh_key()
         key_hint = default_key or t("none")
@@ -849,14 +851,12 @@ class TODO:
             parts.append("sudo")
         parts.append(script_path)
         parts += ["--name", name, "--version", version]
-        parts += [
-            "--memory",
-            memory,
-            "--vcpus",
-            vcpus,
-            "--disk-size",
-            disk_size,
-        ]
+        if memory:
+            parts += ["--memory", memory]
+        if vcpus:
+            parts += ["--vcpus", vcpus]
+        if disk_size:
+            parts += ["--disk-size", disk_size]
         if ssh_key:
             parts += ["--ssh-key", ssh_key]
         if use_password:
diff --git a/script/todo/todo_i18n.py b/script/todo/todo_i18n.py
index 8f44ea9..0391fcb 100644
--- a/script/todo/todo_i18n.py
+++ b/script/todo/todo_i18n.py
@@ -1041,17 +1041,17 @@ TRANSLATIONS = {
         "fr": "Nom de la VM : ",
         "en": "VM name: ",
     },
-    "RAM in MB (default: 8192): ": {
-        "fr": "RAM en Mo (défaut : 8192) : ",
-        "en": "RAM in MB (default: 8192): ",
+    "RAM in MB (blank = version minimum): ": {
+        "fr": "RAM en Mo (vide = minimum de la version) : ",
+        "en": "RAM in MB (blank = version minimum): ",
     },
-    "vCPUs (default: 4): ": {
-        "fr": "vCPU (défaut : 4) : ",
-        "en": "vCPUs (default: 4): ",
+    "vCPUs (default: 2): ": {
+        "fr": "vCPU (défaut : 2) : ",
+        "en": "vCPUs (default: 2): ",
     },
-    "Disk size (default: 20G): ": {
-        "fr": "Taille du disque (défaut : 20G) : ",
-        "en": "Disk size (default: 20G): ",
+    "Disk size (blank = version minimum): ": {
+        "fr": "Taille du disque (vide = minimum de la version) : ",
+        "en": "Disk size (blank = version minimum): ",
     },
     "SSH public key path": {
         "fr": "Chemin de la clé publique SSH",