tools: nm-in-vm: change default image size

Images of qcow2 format dynamically grow up to the maximum size that they
have been configured at creation time. Because of this, higher size can
be selected without wasting unnecesary space in the host. Rise image
size to 20G.

Also, allow to set an empty value to IMAGE_SIZE, and don't resize in
that case. This is useful because virt-resize fails with some guest
partition layouts (like with ubuntu-20.04).

tools/nm-in-vm

@@ -65,7 +65,7 @@ fi
 VM=${VM:="nm"}
 OS_VERSION=${OS_VERSION:=}
 RAM=${RAM:=2048}
-IMAGE_SIZE=${IMAGE_SIZE:=10G}
+IMAGE_SIZE=${IMAGE_SIZE=20G}
 ROOT_PASSWORD=${ROOT_PASSWORD:=nm}
 LIBVIRT_POOL=${LIBVIRT_POOL:=default}  # only useful if BASEDIR_VM_IMAGE is empty
 BASEDIR_VM_IMAGE=${BASEDIR_VM_IMAGE:=}
@@ -104,6 +104,8 @@ fi
 
 do_build() {
     local t=$'\t'
+    local ram
+    local size
     local os_variant
     local nm_ci_build_args
     local nm_ci_install_args
@@ -141,6 +143,10 @@ do_build() {
         return 0
     fi
 
+    if [[ -n $IMAGE_SIZE ]]; then
+        size=(--size "$IMAGE_SIZE")
+    fi
+
     if [[ -n $BASEDIR_NM_CI ]]; then
         nm_ci_build_args=(
             --mkdir "$BASEDIR_NM_CI"
@@ -223,7 +229,7 @@ do_build() {
     echo "Creating VM"
     echo " - VM NAME: $VM"
     echo " - OS VERSION: $OS_VERSION"
-    echo " - SIZE: $IMAGE_SIZE"
+    echo " - SIZE: $([[ -n $IMAGE_SIZE ]] && echo "$IMAGE_SIZE" || echo "don't resize")"
     echo " - RAM: $RAM"
     echo " - ROOT PASSWORD: $ROOT_PASSWORD"
     echo " - IMAGE PATH: $basedir_vm_image/$vm_image_file"
@@ -233,7 +239,7 @@ do_build() {
     
     virt-builder "$OS_VERSION" \
         --output "$basedir_vm_image/$vm_image_file" \
-        --size "$IMAGE_SIZE" \
+        "${size[@]}" \
         --format qcow2 \
         --arch x86_64 \
         --hostname "$VM" \