Elastic Compute Service:Initialize a data disk (Linux)

Method 1: Automatically initialize a data disk using Cloud Assistant (invitational preview)

If you are attaching a data disk and accidentally close the Cloud Assistant initialization dialog box, you can go to the Block Storage tab on the instance details page to initialize the disk using Cloud Assistant.

Method 2: Log on to the instance to manually initialize a data disk

This section uses Alibaba Cloud Linux 3 as an example. The commands may vary based on the operating system. Run the commands that are applicable to your environment.

Step 1: Log on to the ECS instance and view the data disk

1. Remotely connect to the ECS instance.

   For more information, see Log on to a Linux instance using Workbench.

2. Run the following command to determine the device name of the data disk that you want to initialize.

   sudo fdisk -lu
   sudo blkid

   The sample output shows that three disks are attached to the ECS instance:

   • /dev/vda is the system disk. A system disk created with an instance is initialized by default and does not need to be re-initialized.

   • /dev/vdb is a data disk. It does not have a partition, such as /dev/vdb1, but has an ext4 file system. It does not need to be re-initialized.

   • /dev/vdc is a data disk. The sudo blkid command does not return information for this disk, which indicates that it is not initialized. You must initialize this disk.

   In this example, the device name of the data disk to initialize is /dev/vdc.

   

3. Determine which initialization steps to perform.

   • If you want to use partitions to categorize, store, and manage data, and the disk capacity is greater than 2 TiB or will be extended to more than 2 TiB: Due to partition format limitations, you can only create GPT partitions. You must perform the operations in Create a GPT partition (Recommended) and Step 3: Create and mount a file system.

   • If you want to use partitions to categorize, store, and manage data, and the disk capacity is 2 TiB or less with no plans to extend it beyond 2 TiB: You can create a GPT partition (recommended) or an MBR partition. You must perform the operations in Step 2: Create a partition for the data disk and Step 3: Create and mount a file system.

   • If you want to create a file system directly on a raw device without creating partitions: You can skip creating a partition and proceed directly to Step 3: Create and mount a file system.

(Conditional) Step 2: Create a partition for the data disk

1. See Determine which initialization steps to perform to determine whether you need to create a partition on the disk.

2. Run the command to create a partition.

   Important

   • The maximum partition size and the maximum number of partitions per disk vary based on the partition format. For more information, see Introduction to partition formats.

   • If you plan to extend the disk to more than 2 TiB in the future, you must use a GPT partition. Due to the capacity limit of MBR partitions, you cannot directly extend the disk to the desired capacity. This may require you to re-partition and format the disk, which would cause data loss.

   Create a GPT partition (recommended)

   1. Run the following command to install the Parted tool.

      sudo yum install -y parted

      Note

      The yum command applies to Linux distributions such as CentOS. For other Linux distributions, modify the installation command based on the package manager you use. For example, on Debian or Ubuntu, run the following command to install the Parted tool:

      sudo apt-get update
      sudo apt-get install -y parted

   2. Use the Parted tool to partition the data disk.

      1. Run the following command to start partitioning. This example uses the data disk /dev/vdb.

         sudo parted /dev/vdb

         Replace /dev/vdb with the device name of the data disk that you want to partition.

      2. In the Parted interactive command line, run the following command to set the partition format to GPT.

         mklabel gpt

      3. Run the following command to create a partition and set its start and end positions.

         mkpart <PartitionName> <StartPosition> <EndPosition>

         Important

         Use binary units, such as MiB or GiB, for the start and end positions of the partition. After creation, the partition is 4 KiB-aligned. If you do not use these units, the partition may not be aligned, which can severely affect disk performance.

         Set <PartitionName>, <StartPosition>, and <EndPosition> based on your requirements.

         • Single partition example: To create one primary partition named primary that starts at 1 MiB and uses 100% of the disk capacity, run the following command:

           mkpart primary 1MiB 100%

         • Multiple partitions example: To create two partitions, where the first partition is named primary and has a capacity of 20 GiB, and the second partition is named secondary and uses the remaining capacity, run the following commands:

           mkpart primary 1MiB 20GiB
           mkpart secondary 20GiB 100%

      4. Run the following command to check if the partition is aligned.

         In the command, 1 is the partition number. We recommend that you align partitions to achieve optimal disk performance.

         align-check optimal 1

         If the partition is aligned, the following output is returned:

         1 aligned

         Important

         If 1 not aligned is returned, the partition is not aligned. To resolve this issue, see FAQ about disk initialization.

      5. Run the following command to view the partition table.

         print

      6. (Optional) If you made a mistake during partitioning, run the rm command followed by the partition number to delete the incorrect partition. Then, repeat the required steps. The following figure shows an example of how to find a partition using the print command and delete the incorrect partition whose number is 2.

         Important

         Before you delete a partition, make sure that it contains no data or that the data has been backed up.

      7. Run the following command to exit the Parted tool.

         quit

      The partitioning process is as follows.

      

   3. Run the following command to make the operating system re-read the partition table.

      partprobe

   4. Run the following command to view information about the new partition on the data disk /dev/vdb.

      sudo fdisk -lu /dev/vdb

      Replace /dev/vdb with the device name of the data disk in your environment.

      The following output is returned. If the Disk label type is gpt, a new partition has been created.

      

      Note

      • The display may vary slightly depending on the operating system. If the Disk label type field is not present, you can determine the partition type from the System field. A System value of Linux indicates an MBR partition, and GPT indicates a GPT partition.

      • Older versions of fdisk may not display GPT partition tables correctly. You can run the gdisk -l /dev/vdb command to view the partition type.

   Create an MBR partition

   1. Create an MBR partition.

      1. Run the following command to partition the data disk. This example uses the data disk /dev/vdb.

         sudo fdisk -u /dev/vdb

         Replace /dev/vdb with the device name of the data disk that you want to partition.

         The following information is returned.

         

      2. In the fdisk interactive command line, enter p and press the Enter key to view the partition status of the data disk.

         The following information is returned.

         

      3. Enter n and press the Enter key to start creating a new partition.

         The following information is returned.

         

         The disk supports two partition types:

         • p indicates a primary partition.

         • e indicates an extended partition.

           Note

           For more information about partitions, see Introduction to partition formats.

      4. This example creates a primary partition. Enter p and press the Enter key to start creating a primary partition.

         The following information is returned.

         

         Partition number indicates the primary partition number. You can choose a number from 1 to 4.

      5. Enter the partition number and press the Enter key.

         This example creates one primary partition. Press the Enter key to use the default partition number 1 for the primary partition.

         The following information is returned.

         

      6. Enter the starting sector number and press the Enter key.

         First sector indicates the starting sector number of the available partition space. You can choose a number from 2048 to 83886079. The default value is 2048. In this example, press the Enter key to select the default starting sector number 2048.

         The following information is returned.

         

         Note

         The system automatically prompts for the starting and ending sector numbers of the available partition space. You can customize them within this range or use the default values. The starting sector number must be smaller than the ending sector number.

      7. Enter the last sector number and press the Enter key.

         Last sector indicates the ending sector number of the available partition space. You can choose a number from 2048 to 83886079. The default value is 83886079. In this example, press the Enter key to select the default ending sector number 83886079.

         The following information is returned.

         

         Note

         The system automatically prompts for the starting and ending sector numbers of the available partition space. You can customize them within this range or use the default values. The starting sector number must be smaller than the ending sector number.

      8. Enter p and press the Enter key to view the partition layout of the data disk.

         The following information is returned, which shows the details of the new partition /dev/vdb1.

         

         Note

         If you made a mistake in the previous steps, enter q to exit the fdisk tool. The changes are not saved. You can then re-partition the disk by following the preceding steps.

      9. Enter w and press the Enter key to write the changes to the partition table.

         The following information is returned, which indicates that the partition is created.

         

   2. (Optional) To create multiple partitions for a single disk, repeat step a for each partition.

   3. Run the following command to view the new partition information. This example uses the data disk /dev/vdb.

      sudo fdisk -lu /dev/vdb

      Replace /dev/vdb with the device name of the data disk based on your environment.

      The following output is returned. If /dev/vdb1 is displayed and the value of Disk label type is dos, the new MBR partition is created.

      

      Note

      • The output may vary slightly depending on the operating system. If the Disk label type field is not displayed, you can determine the partition type from the System field. A System value of Linux indicates an MBR partition, and a value of GPT indicates a GPT partition.

      • Older versions of fdisk may not display GPT partition tables correctly. You can run the gdisk -l /dev/vdb command to view the partition type.

Step 3: Create and attach a file system

Regardless of whether the disk is partitioned, you must create and mount a file system before you can use the disk. Different file systems support different partition sizes. Create a file system based on your requirements.

1. Run the following command to create a file system. The following example commands describe how to create an ext4 and an xfs file system.

   Create an ext4 file system

   1. Run the following command to install the e2fsprogs tool.

      The yum command in this step applies to Linux distributions such as CentOS. For other Linux distributions, modify the installation command based on the package manager you use. For example, on Debian or Ubuntu, use apt-get install <PackageName>.

      sudo yum install -y e2fsprogs

   2. Create an ext4 file system.

      Note

      If you plan to extend the disk to 64 TiB in the future, add the -i 65536 parameter to the command to specify 65536 for bytes-per-inode.

      • To create an ext4 file system for the partition /dev/vdb1, run the following command:

        sudo mkfs -t ext4 /dev/vdb1

        Replace /dev/vdb1 with the name of the data disk partition based on your environment.

      • To create an ext4 file system for the bare device /dev/vdc, run the following command:

        sudo mkfs -t ext4 /dev/vdc

        Replace /dev/vdc with the name of the bare device based on your environment.

      Note

      • If an error is reported when you create an ext4 file system for a 16 TiB data disk, the e2fsprogs package version may be earlier than 1.42. To upgrade the e2fsprogs package to version 1.42 or later, see How do I upgrade the e2fsprogs package?.

      • The lazy init feature of ext4 file systems affects the I/O performance of data disks. You can disable this feature. For more information, see How do I disable the lazy init feature for a Linux instance?.

   Create an xfs file system

   1. Run the following command to install the xfsprogs tool.

      sudo yum install -y xfsprogs

      Note

      The yum command in this step is for Linux distributions such as CentOS. For other Linux distributions, you can modify the installation command according to your package manager. For example, on Debian or Ubuntu, you can use apt-get install <PackageName>.

   2. Create an xfs file system.

      • To create an xfs file system for the partition /dev/vdb1, run the following command:

        sudo mkfs -t xfs /dev/vdb1

        Replace /dev/vdb1 with the name of the data disk partition based on your environment.

      • To create an xfs file system for the bare device /dev/vdc, run the following command:

        sudo mkfs -t xfs /dev/vdc

        Replace /dev/vdc with the name of the bare device based on your environment.

2. Run the following command to mount the file system.

   • To mount the partition /dev/vdb1 to the /mnt folder, run the following command:

     sudo mount /dev/vdb1 /mnt

     Replace /dev/vdb1 with the name of the data disk partition based on your environment. Replace /mnt with the mount target of the partition. The mount target can be an existing empty folder, or you can run the sudo mkdir -p <NewFolder> command to create a new folder as the mount target, such as sudo mkdir -p /data.

     Important

     If the mount target folder contains data, the mount operation hides the original files in the folder. This makes the original files inaccessible and can affect your services.

   • To attach the bare device /dev/vdc to the /tmp folder, run the following command:

     sudo mount /dev/vdc /tmp

     Replace /dev/vdc with the name of the bare device for your environment. Replace /tmp with the mount target of the partition. The mount target can be an existing empty folder, or you can create a new one by running the sudo mkdir -p <NewFolder> command, such as sudo mkdir -p /data.

     Important

     If the target mount folder already contains data, the configuration will hide the folder's original content. This can cause data loss and disrupt your services.

3. Run the following command to check whether the file system is mounted as expected.

   df -Th

   The following output is returned. If information about the new file system is displayed, the file system is mounted.

   

(Optional) Step 4: Configure a partition to auto-attach at startup

1. Run the following command to back up the /etc/fstab file.

   sudo cp /etc/fstab /etc/fstab.bak

2. Write the new partition information to the /etc/fstab file.

   sudo sh -c "echo `sudo blkid /dev/vdb1 | awk '{print \$2}' | sed 's/\"//g'` /mnt ext4 defaults 0 0 >> /etc/fstab"

   Note

   Ubuntu 12.04 does not support barriers. You must run the following command: sudo sh -c "echo `sudo blkid /dev/vdb1 | awk '{print $2}' | sed 's/\"//g'` /mnt ext4 barrier=0 0 0 >> /etc/fstab".

   The parameters are described as follows:

   • /dev/vdb1: The name of the data disk partition. Replace it based on your environment. You can obtain it by running the df -Th command.

   • /mnt: The mount target of the partition. Replace it with the mount target you have set. You can obtain it by running the df -Th command.

   • ext4: The file system type of the partition. Replace it with the file system type you have created. You can obtain it by running the df -Th command.

   • defaults: The mount parameters of the file system. You can select the mount parameters that meet your requirements. For more information, see the fstab description.

     Note

     If you set the parameter to defaults,nofail, the instance can start even if the mount configuration is incorrect. However, the system does not report an error. You must check whether the automatic mount is successful to prevent data from being written to the wrong location due to configuration errors.

3. (Conditional) If a single disk has multiple partitions, you must add an entry for each partition to the /etc/fstab file.

   For example, if the data disk /dev/vdb has two partitions, /dev/vdb1 and /dev/vdb2, you must run the following commands:

   sudo sh -c "echo `sudo blkid /dev/vdb1 | awk '{print \$2}' | sed 's/\"//g'` <MountTargetOf/dev/vdb1> <FileSystemTypeOf/dev/vdb1> defaults 0 0 >> /etc/fstab"
   sudo sh -c "echo `sudo blkid /dev/vdb2 | awk '{print \$2}' | sed 's/\"//g'` <MountTargetOf/dev/vdb2> <FileSystemTypeOf/dev/vdb2> defaults 0 0 >> /etc/fstab"

4. Run the following command to view the new partition information in the /etc/fstab file.

   cat /etc/fstab

   The following output is returned. You can view the configured partition information for /dev/vdb1.

   

   Note

   If the partition information is incorrect, you can manually edit the /etc/fstab file to delete the incorrect entry and then add the correct entry. For more information, see Automatically mount a data disk using its UUID in the fstab file.

5. Run the following command to verify that the automatic mount feature is effective.

   sudo umount /dev/vdb1
   sudo mount -a
   mount | grep /mnt

   Run the `df -Th` command. The following output is returned. You can view the file system mount information, which indicates that the automatic mount feature is effective.

   

FAQ about disk initialization

mkfs.ext4: Size of device /dev/vdb too big to be expressed in 32 bits using a blocksize of 4096.            

sudo mke2fs -O 64bit,has_journal,extents,huge_file,flex_bg,uninit_bg,dir_nlink,extra_isize -E lazy_itable_init=0,lazy_journal_init=0 /dev/vdb1

References

If a disk has insufficient storage space, you can extend it to increase its capacity. For more information, see Extend a disk (Linux).