How Do I Configure a Linux Private Image to Make It Automatically Expand Its Root Partition?

Constraints

• An image whose root partition file system is xfs cannot automatically expand its partitions.
• An image that has the LVM partition cannot automatically expand its partitions.
• Images whose file system is ext3 or ext4 are recommended.
  

  After OS partitions of old versions are expanded, the OS must be restarted to update the file system.

Installation of growpart on Different OSs

For Debian 9, use method 1 to install growpart. If the installation fails, use method 2 to install growpart.

Method 1:

Run the following command to install growpart:

apt-get install -y -f cloud-init cloud-utils cloud-initramfs-growroot

Method 2:

If method 1 fails, it may be because the installation source of Debian 9.0.0 is faulty. You need to download dependent packages cloud-utils and cloud-initramfs-growroot and install them.

1. Run the following command to download the dependent packages:

   wget Package download path

   You can obtain the dependent packages from the following paths:

   http://ftp.br.debian.org/debian/pool/main/c/cloud-utils/cloud-utils_0.29-1_all.deb

   http://ftp.br.debian.org/debian/pool/main/c/cloud-initramfs-tools/cloud-initramfs-growroot_0.18.debian5_all.deb

2. Run the following command to rectify the dependent packages:

   apt --fix-broken install

3. Run the following command to install the dependent packages:

   dpkg -i cloud-utils package path cloud-initramfs-growroot package path

   An example command is dpkg -i /root/cloud-utils_0.29-1_all.deb /root/cloud-initramfs-growroot_0.18.debian5_all.deb.

For other Debian versions, run the following command to install dependent packages:

apt-get update;apt-get install cloud-utils cloud-initramfs-growroot

Procedure

Take the following as two examples of image disk partitioning:

If the root partition is the last partition, see Root partition at the last.

If the root partition is not the last partition, see Root partition not at the last.

If the parted command fails, ensure that the parted tool has been installed in the OS. Perform the following operations to install the tool:

• For CentOS, run the following command:

  yum install parted

• For Debian, run the following command:

  apt-get install parted

• Root partition at the last (/dev/xvda1: swap and /dev/xvda2: root)

  For example, if the system disk size of CentOS 6.5 64bit is 40 GB, perform the following operations to configure a Linux private image so that it can automatically expand its root partition:

  1. Run the following command to query the partitions of /dev/xvda:

     parted -l /dev/xvda

     As shown in the command output, the root partition is the second partition and is 38.7 GB.

     Model: Xen Virtual Block Device (xvd)
     Disk /dev/xvda: 42.7GB
     Sector size (logical/physical): 512B/512B
     Partition Table: msdos
     
     Number Start End Size Type File system Flags
     1 1049kB 4296MB 4295MB primary linux-swap(v1)
     2 4296MB 42.9GB 38.7GB primary ext4 boot

  2. Install growpart to ensure that the image can automatically expand its root partition.

     Run the following command to install growpart:

     yum install cloud-*

     

     growpart may be contained in the cloud-utils-growpart/cloud-utils/cloud-initramfs-tools/cloud-init package. You can run the preceding command directly and then run the growpart command to check whether growpart has been installed successfully.

  3. Run the following command to obtain the file system type and UUID:

     blkid

     The command output is as follows:

     /dev/xvda1: UUID="25ec3bdb-ba24-4561-bcdc-802edf42b85f" TYPE="swap" 
     /dev/xvda2: UUID="1a1ce4de-e56a-4e1f-864d-31b7d9dfb547" TYPE="ext4" 

  4. Stop the ECS and use it to create a private image.

     [root@sluo-ecs-e6dc-resizefs ~]# poweroff 
     Connection closed by foreign host.
     Disconnected from remote host at 11:08:54.
     Type `help´ to learn how to use Xshell prompt.

  5. Use the created image to create an ECS with a 50 GB system disk. Log in to the ECS and run the following command to query the expanded partitions:

     parted -l /dev/xvda

     As shown in the command output, the root partition has been expanded automatically.

     Model: Xen Virtual Block Device (xvd)
     Disk /dev/xvda: 53.7GB
     Sector size (logical/physical): 512B/512B
     Partition Table: msdos
     
     NumberStartEndSizeTypeFile systemFlags
     1 1049kB 4296MB 4295MB primary linux-swap(v1)
     2 4296MB 53.7GB 49.4GB primary ext4 boot

  6. Run the following command to check whether disks are attached to the ECS successfully:

     df -Th

     The command output is as follows:

     Filesystem     Type      Size    Used   Avail Use%  Mounted on
     /dev/xvda2     ext4      49.4G    2.6G  46.8G  4%   /dev/shm
     tmpfs          tmpfs     4295M    0     4295M  0%   / 

• Root partition not at the last (for example, /dev/xvda1: root and /dev/xvda2: swap)
  For example, if the system disk size of CentOS 7.3 64bit is 40 GB, perform the following operations to configure a Linux private image so that it can automatically expand its root partition:

  1. Run the following command to query the partitions of /dev/xvda:

     parted -l /dev/xvda

     As shown in the command output, the root partition is the first partition and is 40.9 GB. The swap partition is the second partition.

     Model: Xen Virtual Block Device (xvd)
     Disk /dev/xvda: 42.9GB
     Sector size (logical/physical): 512B/512B
     Partition Table: msdos
     Disk Flags: 
     
     Number  Start   End     Size    Type     File system     Flags
     1      1049kB  41.0GB  40.9GB  primary  ext4            boot
     2      41.0GB  42.9GB  2000MB  primary  linux-swap(v1)

  2. Run the following command to check the configuration of the /etc/fstab file:

     tail -n 3 /etc/fstab

     As shown in the command output, UUIDs of the two partitions are displayed.

     #
     UUID=7c4fce5d-f8f7-4ed6-8463-f2bd22d0ddea /                       ext4    defaults        1 1
     UUID=5de3cf2c-30c6-4fb2-9e63-830439d4e674 swap                    swap    defaults        0 0

  3. Run the following command to open the /etc/fstab file and press i to enter editing mode:

     vi /etc/fstab

  4. Delete the swap partition configuration, press Esc to exit editing mode, and run the following command to save the configuration:

     wq!

  5. Run the following command to check whether the configuration has been modified:

     tail -n 3 /etc/fstab

     As shown in the command output, only the UUID of the root partition is displayed.

     UUID=7c4fce5d-f8f7-4ed6-8463-f2bd22d0ddea /                       ext4    defaults        1 1

  6. Run the following command to stop the swap device:

     swapoff -a

  7. Run the following command to query the partitions of /dev/xvda:

     parted /dev/xvda

     The command output is as follows:

     [root@test-0912 bin]# parted /dev/xvda
     GNU Parted 3.1
     Using /dev/xvda
     Welcome to GNU Parted! Type 'help' to view a list of commands.
     (parted) 

  8. Run the following command to query the disk partitions:

     p

     The command output is as follows:

     (parted) p                                                     
     Model: Xen Virtual Block Device (xvd)
     Disk /dev/xvda: 42.9GB
     Sector size (logical/physical): 512B/512B
     Partition Table: msdos
     Disk Flags: 
     
     Number  Start   End     Size    Type     File system     Flags
      1      1049kB  4296MB  4295MB  primary  linux-swap(v1)
      2      4296MB  42.9GB  38.7GB  primary  xfs             boot
     (parted) 

  9. Run the following command to delete the second partition:

     rm 2

     The command output is as follows:

     (parted) rm 2
     (parted)

  10. Run the following command to query the disk partitions:

      p

      The command output is as follows:

      (parted) p                                                               
      Model: Xen Virtual Block Device (xvd)
      Disk /dev/xvda: 42.9GB
      Sector size (logical/physical): 512B/512B
      Partition Table: msdos
      Disk Flags: 
      
      Number  Start   End     Size    Type     File system  Flags
      1      1049kB  41.0GB  40.9GB  primary  ext4         boot

  11. Enter quit.
  12. Run the following command to query the partitions of /dev/xvda:

      parted -l /dev/xvda

      As shown in the command output, the swap partition is deleted.

      Model: Xen Virtual Block Device (xvd)
      Disk /dev/xvda: 42.9GB
      Sector size (logical/physical): 512B/512B
      Partition Table: msdos
      Disk Flags: 
      
      Number  Start   End     Size    Type     File system  Flags
      1      1049kB  41.0GB  40.9GB  primary  ext4         boot

  13. Install growpart to ensure that the image can automatically expand its root partition.

      Run the following command to install growpart:

      yum install cloud-*

      

      growpart may be contained in the cloud-utils-growpart/cloud-utils/cloud-initramfs-tools/cloud-init package. You can run the preceding command directly and then run the growpart command to check whether growpart has been installed successfully.

  14. Run the following command to expand the swap partition of the /dev/xvda disk to the first partition to which the root partition belongs:

      growpart /dev/xvda 1

      The command output is as follows:

      CHANGED: partition=1 start=2048 old: size=79978496 end=79980544 new: size=83873317,end=83875365

  15. Run the following command to query the partitions of /dev/xvda:

      parted -l /dev/xvda

      The command output is as follows:

      Model: Xen Virtual Block Device (xvd)
      Disk /dev/xvda: 42.9GB
      Sector size (logical/physical): 512B/512B
      Partition Table: msdos
      Disk Flags: 
      
      Number  Start   End     Size    Type     File system  Flags
      1      1049kB  42.9GB  42.9GB  primary  ext4         boot

  16. Run the following command to obtain the file system type and UUID:

      blkid

      The command output is as follows:

      /dev/xvda1: UUID="7c4fce5d-f8f7-4ed6-8463-f2bd22d0ddea" TYPE="ext4" 

  17. Stop the ECS and use it to create a private image.

      [root@sluo-ecs-e6dc-resizefs ~]# poweroff 
      Connection closed by foreign host.
      Disconnected from remote host at 11:08:54.
      Type `help´ to learn how to use Xshell prompt.

  18. Use the created image to create an ECS with a 100 GB system disk. Log in to the ECS and run the following command to query the partitions of /dev/xvda:

      parted -l /dev/xvda

      As shown in the command output, the root partition has been expanded to 107 GB.

      Model: Xen Virtual Block Device (xvd)
      Disk /dev/xvda: 107GB
      Sector size (logical/physical): 512B/512B
      Partition Table: msdos
      Disk Flags: 
      
      Number  Start   End    Size   Type     File system  Flags
       1      1049kB  107GB  107GB  primary  ext4         boot
      

      

      The value of Size is the size of the expanded root partition.