Changing Disk Identifiers in the GRUB File to UUID

To ensure that Linux can correctly identify disks when starting the file system, you need to change the disk identifier in the GRUB file of the ECS to UUID before creating a Linux private image.

Modify the menu.lst or grub.cfg file (/boot/grub/menu.lst, /boot/grub/grub.cfg, /boot/grub2/grub.cfg, /boot/grub/grub.conf, or /boot/efi/EFI/euleros/grub.cfg), and configure the boot partition using a UUID.

• Ubuntu 14.04: Run blkid to obtain the UUID of the root partition. Modify the /boot/grub/grub.cfg file and use the UUID of the root partition to configure the boot item. If the root partition already uses UUID, no change is required. The procedure is as follows:
  1. Log in to an ECS as user root.
  2. List all types of mounted file systems and their device UUIDs.

     blkid

     The command output is as follows:

      /dev/xvda1: UUID="ec51d860-34bf-4374-ad46-a0c3e337fd34"  TYPE="ext3"
      /dev/xvda5: UUID="7a44a9ce-9281-4740-b95f-c8de33ae5c11"  TYPE="swap"
     
     

  3. Query the grub.cfg file.

     cat /boot/grub/grub.cfg

     The command output is as follows:

     ......menuentry 'Ubuntu Linux, with Linux 3.13.0-24-generic' --class ubuntu --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.13.0-24-generic-advanced-ec51d860-34bf-4374-ad46-a0c3e337fd34' {
     recordfail
     load_video
     gfxmode $linux_gfx_mode
     insmod gzio
     insmod part_msdos
     insmod ext2
     if [ x$feature_platform_search_hint = xy ]; then
     search --no-floppy --fs-uuid --set=root ec51d860-34bf-4374-ad46-a0c3e337fd34
     else
     search --no-floppy --fs-uuid --set=root ec51d860-34bf-4374-ad46-a0c3e337fd34
     fi
     echo 'Loading Linux 3.13.0-24-generic ...'
     linux /boot/vmlinuz-3.13.0-24-generic  root=/dev/xvda1  ro 
     echo 'Loading initial ramdisk ...'
     initrd /boot/initrd.img-3.13.0-24-generic 
     }
     
     

  4. Check whether the root partition in the /boot/grub/grub.cfg configuration file contains root=/dev/xvda1 or root=UUID=ec51d860-34bf-4374-ad46-a0c3e337fd34.
     • If root=UUID=ec51d860-34bf-4374-ad46-a0c3e337fd34 is contained, the root partition is in UUID format and requires no change.
     • If root=/dev/xvda1 is contained, the root partition is in the device name format. Go to 5.
  5. Identify the UUID of the root partition device based on root=/dev/xvda1 (device name of the root partition) and the partition information obtained by running the blkid command.
  6. Open the grub.cfg file.

     vi /boot/grub/grub.cfg

  7. Press i to enter insert mode and change the root partition to the UUID format, for example, from root=/dev/xvda1 to root=UUID=ec51d860-34bf-4374-ad46-a0c3e337fd34.
  8. Press Esc, enter :wq, and press Enter. The system saves the configuration and exits the vi editor.
  9. Verify the change.

     cat /boot/grub/grub.cfg

     The change is successful if information similar to the following is displayed:

     ......menuentry 'Ubuntu Linux, with Linux 3.13.0-24-generic' --class ubuntu --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.13.0-24-generic-advanced-ec51d860-34bf-4374-ad46-a0c3e337fd34' {
     recordfail
     load_video
     gfxmode $linux_gfx_mode
     insmod gzio
     insmod part_msdos
     insmod ext2
     if [ x$feature_platform_search_hint = xy ]; then
     search --no-floppy --fs-uuid --set=root ec51d860-34bf-4374-ad46-a0c3e337fd34
     else
     search --no-floppy --fs-uuid --set=root ec51d860-34bf-4374-ad46-a0c3e337fd34
     fi
     echo 'Loading Linux 3.13.0-24-generic ...'
     linux /boot/vmlinuz-3.13.0-24-generic  root=UUID=ec51d860-34bf-4374-ad46-a0c3e337fd34  ro
     echo 'Loading initial ramdisk ...'
     initrd /boot/initrd.img-3.13.0-24-generic
     }
     
     

• CentOS 6.5: Run blkid to obtain the UUID of the root partition. Modify the /boot/grub/grub.conf file and use the UUID of the root partition to configure the boot item. If the root partition already uses UUID, no change is required. The procedure is as follows:
  1. Log in to an ECS as user root.
  2. List all types of mounted file systems and their device UUIDs.

     blkid

     The command output is as follows:

      /dev/xvda1: UUID="749d6c0c-990a-4661-bed1-46769388365a"  TYPE="swap"  
      /dev/xvda2: UUID="f382872b-eda6-43df-9516-5a687fecdce6"  TYPE="ext4"
     
     

  3. Query the grub.conf file.

     cat /boot/grub/grub.conf

     The command output is as follows:

     default=0 
     timeout=5 
     splashimage=(hd0,1)/boot/grub/splash.xpm.gz 
     hiddenmenu 
     title CentOS (2.6.32-573.8.1.el6.x86_64) 
     root (hd0,1) 
     kernel /boot/vmlinuz-2.6.32-573.8.1.el6.x86_64 ro  root=/dev/xvda2  rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=autoKEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet 
     initrd /boot/initramfs-2.6.32-573.8.1.el6.x86_64.img
     
     

  4. Check whether the root partition in the /boot/grub/grub.conf configuration file contains root=/dev/xvda2 or root=UUID=f382872b-eda6-43df-9516-5a687fecdce6.
     • If root=UUID=f382872b-eda6-43df-9516-5a687fecdce6 is contained, the root partition is in UUID format and requires no change.
     • If root=/dev/xvda2 is contained, the root partition is in the device name format. Go to 5.
  5. Identify the UUID of the root partition device based on root=/dev/xvda2 (device name of the root partition) and the partition information obtained by running the blkid command.
  6. Open the grub.conf file.

     vi /boot/grub/grub.conf

  7. Press i to enter insert mode and change the root partition to the UUID format, for example, from root=/dev/xvda2 to root=UUID=f382872b-eda6-43df-9516-5a687fecdce6.
  8. Press Esc, enter :wq, and press Enter. The system saves the configuration and exits the vi editor.
  9. Verify the change.

     cat /boot/grub/grub.conf

     The change is successful if information similar to the following is displayed:

     default=0 
     timeout=5 
     splashimage=(hd0,1)/boot/grub/splash.xpm.gz 
     hiddenmenu 
     title CentOS (2.6.32-573.8.1.el6.x86_64) 
     root (hd0,1) 
     kernel /boot/vmlinuz-2.6.32-573.8.1.el6.x86_64 ro  root=UUID=f382872b-eda6-43df-9516-5a687fecdce6  rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=autoKEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet 
     initrd /boot/initramfs-2.6.32-573.8.1.el6.x86_64.img
     
     

• CentOS 7.0: Run blkid to obtain the UUID of the root partition. Modify the /boot/grub2/grub.cfg file and use the UUID of the root partition to configure the boot item. If the root partition already uses UUID, no modification is required.
  1. Log in to an ECS as user root.
  2. List all types of mounted file systems and their device UUIDs.

     blkid

     The command output is as follows:

      /dev/xvda2: UUID="4eb40294-4c6f-4384-bbb6-b8795bbb1130"  TYPE="xfs"  
      /dev/xvda1: UUID="2de37c6b-2648-43b4-a4f5-40162154e135"  TYPE="swap" 
     
     

  3. Query the grub.cfg file.

     cat /boot/grub2/grub.cfg

     The command output is as follows:

     ......
     menuentry 'CentOS Linux (3.10.0-229.el7.x86_64) 7 (Core)' --class fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-229.el7.x86_64-advanced-4eb40294-4c6f-4384-bbb6-b8795bbb1130' { 
     load_video 
     set gfxpayload=keep 
     insmod gzio 
     insmod part_msdos 
     insmod xfs 
     set root='hd0,msdos2' 
     if [ x$feature_platform_search_hint = xy ]; then 
     search --no-floppy --fs-uuid --set=root --hint='hd0,msdos2'4eb40294-4c6f-4384-bbb6-b8795bbb1130 
     else 
     search --no-floppy --fs-uuid --set=root 4eb40294-4c6f-4384-bbb6-b8795bbb1130 
     fi 
     linux16 /boot/vmlinuz-3.10.0-229.el7.x86_64  root=/dev/xvda2  ro crashkernel=auto rhgb quiet LANG=en_US.UTF-8 
     initrd16 /boot/initramfs-3.10.0-229.el7.x86_64.img 
     }
     
     

  4. Check whether the root partition in the /boot/grub2/grub.cfg configuration file contains root=/dev/xvda2 or root=UUID=4eb40294-4c6f-4384-bbb6-b8795bbb1130.
     • If root=UUID=4eb40294-4c6f-4384-bbb6-b8795bbb1130 is contained, the root partition is in UUID format and requires no change.
     • If root=/dev/xvda2 is contained, the root partition is in the device name format. Go to 5.
  5. Identify the UUID of the root partition device based on root=/dev/xvda2 (device name of the root partition) and the partition information obtained by running the blkid command.
  6. Open the grub.cfg file.

     vi /boot/grub2/grub.cfg

  7. Press i to enter insert mode and change the root partition to the UUID format, for example, from root=/dev/xvda2 to root=UUID=4eb40294-4c6f-4384-bbb6-b8795bbb1130.
  8. Press Esc, enter :wq, and press Enter. The system saves the configuration and exits the vi editor.
  9. Verify the change.

     cat /boot/grub2/grub.cfg

     The change is successful if information similar to the following is displayed:

     ......
     menuentry 'CentOS Linux (3.10.0-229.el7.x86_64) 7 (Core)' --class fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-229.el7.x86_64-advanced-4eb40294-4c6f-4384-bbb6-b8795bbb1130' { 
     load_video 
     set gfxpayload=keep 
     insmod gzio 
     insmod part_msdos 
     insmod xfs 
     set root='hd0,msdos2' 
     if [ x$feature_platform_search_hint = xy ]; then 
     search --no-floppy --fs-uuid --set=root --hint='hd0,msdos2'4eb40294-4c6f-4384-bbb6-b8795bbb1130 
     else 
     search --no-floppy --fs-uuid --set=root 4eb40294-4c6f-4384-bbb6-b8795bbb1130 
     fi 
     linux16 /boot/vmlinuz-3.10.0-229.el7.x86_64  root=UUID=4eb40294-4c6f-4384-bbb6-b8795bbb1130  ro crashkernel=auto rhgb quiet LANG=en_US.UTF-8 
     initrd16 /boot/initramfs-3.10.0-229.el7.x86_64.img 
     }