Install GRUB on a Linux server

To use Server Migration Center (SMC) to migrate a Linux server to Alibaba Cloud, if the system boot program GRand Unified Bootloader (GRUB) is not installed on the server, you must install GRUB v2.02 or later. If the server runs an early Linux distribution such as CentOS 5 or Debian 7, if the GRUB version is earlier than 2.02, or if the "Do Grub Failed" error message is displayed in the log file, you must upgrade GRUB to v2.02 or later.

1. Log on to the Linux server.
2. Run the following commands to check the paths of the grub, grub-install, and grub-mkconfig files of the current GRUB version:

   which grub

   which grub-install

   which grub-mkconfig

   • If the outputs of preceding commands indicate that one or more of these paths do not exist, GRUB is not installed on the server or the corresponding files are missing. You must perform operations described in the following section to install GRUB.
   • If you can view the paths of all the files, run the following commands to back up the grub, grub-install, and grub-mkconfig files by renaming them. When you install a new GRUB version, the new version overwrites the current version.

     mv /sbin/grub /sbin/grub-old

     mv /sbin/grub-install /sbin/grub-install-old

     mv /sbin/grub-mkconfig /sbin/grub-mkconfig-old

     Note After you use SMC to migrate the server, you can restore the files by changing their names back to the original ones.
3. Install the GRUB dependencies including bison, gcc, and make.

   yum install -y bison gcc make

4. Perform the following operations to install flex:
   1. Check whether the tools folder exists. If the folder does not exist, create it.

      test -d /root/tools || mkdir -p /root/tools

   2. Go to the tools folder and download the flex installation package.

      cd /root/tools
      wget https://github.com/westes/flex/releases/download/v2.6.4/flex-2.6.4.tar.gz

   3. Decompress the flex installation package.

      tar xzf flex-2.6.4.tar.gz

   4. Go to the directory to which the flex installation package is decompressed, and create a folder named build.

      cd flex-2.6.4
      mkdir -p build

   5. Go to the build folder, and compile and install flex.

      cd build
      ../configure

      make && make install

   6. Create the symbolic link.

      ln -s /usr/local/bin/flex /usr/bin/flex

5. Perform the following operations to install GRUB.
   You must use GRUB v2.02 or later for earlier distributions of operating systems such as CentOS 5, Red Hat Enterprise Linux 5, Debian 7, Amazon Linux, and Oracle Linux.

   1. Check whether the tools folder exists. If the folder does not exist, create it.

      test -d /root/tools || mkdir -p /root/tools

   2. Go to the tools folder and download the GRUB v2.02 installation package.

      cd /root/tools
      wget https://alpha.gnu.org/gnu/grub/grub-2.02~rc1.tar.gz

   3. Decompress the GRUB v2.02 installation package.

      tar xzf grub-2.02~rc1.tar.gz

   4. Go to the directory to which the GRUB v2.02 installation package is decompressed, and create a folder named build.

      cd grub-2.02~rc1
      mkdir -p build

   5. Go to the build folder, and compile and install GRUB.

      cd build
      ../configure

      sed -i -e "s/-Werror//" ./grub-core/Makefile
      sed -i -e "s/-Werror//" . /Makefile
      make && make install

   6. Create the symbolic links.

      ln -s /usr/local/sbin/grub-install /sbin/grub-install
      ln -s /usr/local/sbin/grub-mkconfig /sbin/grub-mkconfig

   Note If the -Werror error is reported during compilation, find the makefile compile file, remove the -Werror option from the file, and then try again.
6. Run the following command to check whether GRUB v2.02 is installed or GRUB is upgraded to v2.02:

   grub-install --version