chroot 調整系統 - MBR

1. gdisk 查看開機硬碟 /dev/sda 的分割狀況，/dev/sda2 的掛載 /boot 的開機目錄。

   bash-4.4# gdisk -l /dev/sda
   GPT fdisk (gdisk) version 1.0.3
   
   Partition table scan:
     MBR: protective
     BSD: not present
     APM: not present
     GPT: present
   
   Found valid GPT with protective MBR; using GPT.
   Disk /dev/sda: 937703088 sectors, 447.1 GiB
   Model: INTEL SSDSC2BW48
   Sector size (logical/physical): 512/512 bytes
   Disk identifier (GUID): 2CC0140B-213C-4298-ADF8-603284119E49
   Partition table holds up to 128 entries
   Main partition table begins at sector 2 and ends at sector 33
   First usable sector is 34, last usable sector is 937703054
   Partitions will be aligned on 2048-sector boundaries
   Total free space is 3693 sectors (1.8 MiB)
   
   Number  Start (sector)    End (sector)  Size       Code  Name
      1            2048           43007   20.0 MiB    EF00  EFI System
      2           43008         1026047   480.0 MiB   EF02  BIOS boot partition
      3         1026048       937701375   446.6 GiB   8E00  Linux LVM
   

2. parted 將 /dev/sda2 分割區的 flags boot 關閉，bios_grub 開啟。

   bash-4.4# parted /dev/sda
   GNU Parted 3.2
   Using /dev/sda
   Welcome to GNU Parted! Type 'help' to view a list of commands.
   (parted) set 2 boot off
   (parted) set 2 bios_grub on
   (parted) q
   Information: You may need to update /etc/fstab.
   

3. grub2-install 安裝 bios 開機到硬碟，此例為 /dev/sda。若硬碟由其他系統管理，例如還原卡，則必須安裝到 bios boot 分割區，此例為 /dev/sda2，無法安裝時可使用 –force 選項強制安裝。

   bash-4.4# grub2-install --target=i386-pc /dev/sda
   

4. 退出系統。

   bash-4.4# exit
   exit
   

5. RHEL9 測試，如上第 2 個 partition 設定為 BIOS boot partition，grub2-install 後這個 partition 無法掛載且無法開機，必須另外新增大小 1M 的第 1 個 BIOS boot partition，再 grub2-install，則 BIOS 及 UEFI 開機都沒問題。