grub: save ang read default menu item

If the ISO image has a FAT partition and the image is written to a flash drive, then it is possible to write to this partition of the flash drive. This is necessary, for example, if the user does not want to install the system, but wants to constantly work in LiveCD mode with or without recording sessions. In order for this code to work, you need to make changes to the FAT partition of the image on the flash drive: Add the 1st line to the grub.cfg file: set pfxfat=${prefix} Write a 1kb file grubenv. If grub.cfg contains a line like '^default=id', then the read value is not used.

grub: save ang read default menu item
efec47fa · Dmitriy Terekhin · aed27a30 · efec47fa · efec47fa · efec47fa
Commit efec47fa authored May 19, 2021 by Dmitriy Terekhin
7 changed files
--- a/features.in/grub/cfg.in/00defaults.cfg
+++ b/features.in/grub/cfg.in/00defaults.cfg
@@ -10,3 +10,15 @@ if [ "$grub_platform" = "efi" -a "$grub_cpu" = "x86_64" ]; then
 fi
 if [ "$grub_platform" = "pc" ]; then set linux_suffix='16'; fi
 if [ ! "$lang" ]; then lang=@LOCALE@; fi
+if [ -s $pfxfat/grubenv ]; then
+  load_env --file $pfxfat/grubenv
+  set default="${saved_entry}"
+else
+  default=@default_id@
+fi
+function savedefault {
+  if [ -z "${boot_once}" -a -s $pfxfat/grubenv ]; then
+    saved_entry="${chosen}"
+    save_env --file $pfxfat/grubenv saved_entry
+  fi
+}
--- a/features.in/grub/cfg.in/20install2.cfg
+++ b/features.in/grub/cfg.in/20install2.cfg

-default='linux'
-
 menuentry $"Install "'@distro@' --hotkey 'i' --id 'linux' {
  echo $"Loading Linux vmlinuz$KFLAVOUR ..."
  linux$linux_suffix /boot/vmlinuz$KFLAVOUR fastboot @initrd_bootargs@ @stagename@=altinst ramdisk_size=@altinst_size@ vga=@bootvga@ @bootargs@ $EFI_BOOTARGS lang=$lang

--- a/features.in/grub/cfg.in/30live.cfg
+++ b/features.in/grub/cfg.in/30live.cfg
 menuentry $"LiveCD (no hard disk needed)" --id 'live' {
+  savedefault
  echo $"Loading Linux vmlinuz$KFLAVOUR ..."
  linux$linux_suffix /boot/vmlinuz$KFLAVOUR fastboot live @initrd_bootargs@ @stagename@=live ramdisk_size=@live_size@ showopts lowmem vga=@bootvga@ @bootargs@ $EFI_BOOTARGS lang=$lang
  echo $"Loading initial ramdisk ..."

--- a/features.in/grub/cfg.in/32live_rw.cfg
+++ b/features.in/grub/cfg.in/32live_rw.cfg
 menuentry $"LiveCD with sessions support" --id 'session' {
+  savedefault
  echo $"Loading Linux vmlinuz$KFLAVOUR ..."
  linux$linux_suffix /boot/vmlinuz$KFLAVOUR fastboot live @initrd_bootargs@ @stagename@=live ramdisk_size=@live_size@ showopts live_rw vga=@bootvga@ @bootargs@ $EFI_BOOTARGS lang=$lang
  echo $"Loading initial ramdisk ..."

--- a/features.in/grub/cfg.in/80rescue.cfg
+++ b/features.in/grub/cfg.in/80rescue.cfg
 menuentry $"Rescue LiveCD" --id 'rescue' {
+  savedefault
  echo $"Loading Linux vmlinuz$KFLAVOUR ..."
  linux$linux_suffix /boot/vmlinuz$KFLAVOUR changedisk fastboot live @initrd_bootargs@ @stagename@=rescue ramdisk_size=@rescue_size@ splash=0 showopts @rescue_bootargs@ $EFI_BOOTARGS
  echo $"Loading initial ramdisk ..."

--- a/features.in/grub/cfg.in/82rescue_rw.cfg
+++ b/features.in/grub/cfg.in/82rescue_rw.cfg
 menuentry $"Rescue with sessions support" --id 'rescue_session' {
+  savedefault
  echo $"Loading Linux vmlinuz$KFLAVOUR ..."
  linux$linux_suffix /boot/vmlinuz$KFLAVOUR changedisk fastboot live @initrd_bootargs@ @stagename@=rescue ramdisk_size=@rescue_size@ splash=0 showopts @rescue_bootargs@ $EFI_BOOTARGS live_rw
  echo $"Loading initial ramdisk ..."

--- a/features.in/grub/stage1/scripts.d/01-grub
+++ b/features.in/grub/stage1/scripts.d/01-grub
@@ -36,8 +36,11 @@ if [ -n "$GLOBAL_GRUB_DEFAULT" ]; then
 		exit 1
 	fi
 fi
+DEFAULT="$(grep -i '\-\-id ' "$CFG" | head -1 | rev| cut -f2 -d' ' |rev)"
+if grep -i '@default_id@' "$CFG"; then
+	sed -i "s/@default_id@/$DEFAULT/" "$CFG"
+fi
 if ! grep -i '^\s*\(set\s\+\)\?default=' "$CFG"; then
-	DEFAULT="$(grep -i '\-\-id ' "$CFG" | head -1 | rev| cut -f2 -d' ' |rev)"
 	if [ -n "$DEFAULT" ]; then
 		echo "default=$DEFAULT" >> "$CFG"
 	else