Help Center/ Elastic Volume Service/ User Guide/ Getting Started/ Initialize an EVS Data Disk/ Initializing a Linux Data Disk (parted)
Updated on 2022-12-20 GMT+08:00
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Initializing a Linux Data Disk (parted)

Scenarios

This section uses CentOS 7.4 64bit to describe how to initialize a data disk attached to a server running Linux and use parted to partition the data disk.

The maximum partition size that MBR supports is 2 TiB and that GPT supports is 18 EiB. If the disk size you need to partition is greater than 2 TiB, partition the disk using GPT.

The partitioning tool fdisk is suitable only for MBR partitions, and parted is suitable for both MBR and GPT partitions. For more information, see Introduction to Data Disk Initialization Scenarios and Partition Styles.

The method for initializing a disk varies depending on the OS running on the server. This document is used for reference only. For the detailed operations and differences, see the product documents of the corresponding OS.

Prerequisites

  • A data disk has been attached to a server and has not been initialized.
  • You have logged in to the server.
    • For how to log in to an ECS, see the Elastic Cloud Server User Guide.
    • For how to log in to a BMS, see the Bare Metal Server User Guide.

Creating and Mounting a Partition

The following example shows you how a new partition can be created on a new data disk that has been attached to a server. The partition will be created using parted, and GPT will be used. Furthermore, the partition will be formatted using the ext4 file system, mounted on /mnt/sdc, and configured with automatic mounting at system start.

  1. Run the following command to query information about the new data disk:

    lsblk

    Information similar to the following is displayed: 
    root@ecs-test-0001 ~]# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
vda    253:0    0   40G  0 disk
└─vda1 253:1    0   40G  0 part /
vdb    253:16   0  100G  0 disk

    In the command output, the server contains two disks. /dev/vda is the system disk, and /dev/vdb is the new data disk.

  2. Run the following command to enter parted to partition the new data disk:

    parted New data disk

    In this example, run the following command:

    parted /dev/vdb

    Information similar to the following is displayed: 
    [root@ecs-test-0001 ~]# parted /dev/vdb
GNU Parted 3.1
Using /dev/vdb
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted)

  3. Enter p and press Enter to view the current disk partition style.

    Information similar to the following is displayed: 
    (parted) p
Error: /dev/vdb: unrecognised disk label
Model: Virtio Block Device (virtblk)
Disk /dev/vdb: 107GB
Sector size (logical/physical): 512B/512B
Partition Table: unknown
Disk Flags:
(parted)

    In the command output, the Partition Table value is unknown, indicating that no partition style is set for the new disk.

  4. Run the following command to set the disk partition style:

    mklabel Disk partition style

    In this example, run the following command to set the partition style to GPT: (Disk partition styles can be MBR or GPT.)

    mklabel gpt

    The maximum disk size supported by MBR is 2 TiB, and that supported by GPT is 18 EiB. Because an EVS data disk currently supports up to 32 TiB, use GPT if your disk size is larger than 2 TiB.

    If the partition style is changed after the disk has been used, data on the disk will be cleared. Therefore, select an appropriate partition style when initializing the disk. If you must change the partition style to GPT after a disk has been used, it is recommended that you back up the disk data before the change.

  5. Enter p and press Enter to view the disk partition style.

    Information similar to the following is displayed: 
    (parted) mklabel gpt
(parted) p
Model: Virtio Block Device (virtblk)
Disk /dev/vdb: 107GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start  End  Size  File system  Name  Flags

(parted)

    In the command output, the Partition Table value is gpt, indicating that the disk partition style is GPT.

  6. Enter unit s and press Enter to set the measurement unit of the disk to sector.
  7. Run the following command and press Enter:

    mkpart Partition name Start sector End sector

    In this example, run the following command:

    mkpart test 2048s 100%

    In this example, one partition is created for the new data disk. Variable 2048s indicates the disk start sector, and variable 100% indicates the disk end sector. The two values are used for reference only. You can determine the number of partitions and the partition size based on your service requirements.

    Information similar to the following is displayed: 
    (parted) mkpart opt 2048s 100%
(parted)

  8. Enter p and press Enter to view details about the new partition.

    Information similar to the following is displayed: 
    (parted) p
Model: Virtio Block Device (virtblk)
Disk /dev/vdb: 209715200s
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start  End         Size        File system  Name  Flags
 1      2048s  209713151s  209711104s               test

(parted)

  9. Enter q and press Enter to exit parted.

    Information similar to the following is displayed: 
    (parted) q
Information: You may need to update /etc/fstab.

    You can set automatic disk mounting by updating the /etc/fstab file. Before updating the file, set the file system format for the partition and mount the partition on the mount point.

  10. Run the following command to view the disk partition information:

    lsblk

    Information similar to the following is displayed: 
    [root@ecs-test-0001 ~]# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
vda    253:0    0   40G  0 disk
└─vda1 253:1    0   40G  0 part /
vdb    253:16   0  100G  0 disk
└─vdb1 253:17   0  100G  0 part

    In the command output, /dev/vdb1 is the partition you created.

  11. Run the following command to set the file system format for the new partition:

    mkfs -t File system format /dev/vdb1

    In this example, run the following command to set the ext4 file system for the new partition:

    mkfs -t ext4 /dev/vdb1

    Information similar to the following is displayed: 
    [root@ecs-test-0001 ~]# mkfs -t ext4 /dev/vdb1
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
6553600 inodes, 26213888 blocks
1310694 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2174746624
800 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624, 11239424, 20480000, 23887872

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

    The formatting takes a period of time. Observe the system running status and do not exit.

    The partition sizes supported by file systems vary. Therefore, you are advised to choose an appropriate file system based on your service requirements.

  12. Run the following command to create a mount point:

    mkdir Mount point

    In this example, run the following command to create the /mnt/sdc mount point:

    mkdir /mnt/sdc

    The /mnt directory exists on all Linux systems. If the mount point fails to create, it may be that the /mnt directory has been accidentally deleted. Run the mkdir -p /mnt/sdc command to create the mount point.

  13. Run the following command to mount the new partition on the created mount point:

    mount Disk partition Mount point

    In this example, run the following command to mount the new partition /dev/vdb1 on /mnt/sdc:

    mount /dev/vdb1 /mnt/sdc

  14. Run the following command to view the mount result:

    df -TH

    Information similar to the following is displayed:

    New partition /dev/vdb1 is mounted on /mnt/sdc.

    If the server is restarted, the mounting will become invalid. You can set automatic mounting for partitions at system start by modifying the /etc/fstab file. For details, see Setting Automatic Mounting at System Start.

Setting Automatic Mounting at System Start

Modify the fstab file to set automatic disk mounting at server start. You can also set automatic mounting for the servers containing data. This operation will not affect the existing data.

The following procedure shows how to set automatic disk mounting at server start by using UUIDs to identify disks in the fstab file. You are advised not to use device names to identify disks in the file because a device name may change (for example, from /dev/vdb1 to /dev/vdb2) during the server stop or start, resulting in improper server running after restart.

UUID is the unique character string for disk partitions in a Linux system.

  1. Run the following command to query the partition UUID:

    blkid Disk partition

    In this example, run the following command to query the UUID of the /dev/vdb1 partition:

    blkid /dev/vdb1

    Information similar to the following is displayed:

    [root@ecs-test-0001 ~]# blkid /dev/vdb1
/dev/vdb1: UUID="0b3040e2-1367-4abb-841d-ddb0b92693df" TYPE="ext4"

    The UUID of the /dev/vdb1 partition is displayed.

  2. Run the following command to open the fstab file using the vi editor:

    vi /etc/fstab

  3. Press i to enter editing mode.
  4. Move the cursor to the end of the file and press Enter. Then, add the following information: 

    UUID=0b3040e2-1367-4abb-841d-ddb0b92693df /mnt/sdc                ext4    defaults        0 2
    The preceding content is used for reference only. Add the information that is used in the environment. The parameters are described as follows:
    • The first column indicates the partition UUID obtained in 1.
    • The second column indicates the directory on which the partition is mounted. You can query the mount point using the df -TH command.
    • The third column indicates the file system format of the partition. You can query the file system format using the df -TH command.
    • The fourth column indicates the partition mount option. Normally, this parameter is set to defaults.
    • The fifth column indicates the Linux dump backup option.
      • 0: Linux dump backup is not used. Normally, dump backup is not used, and you can set this parameter to 0.
      • 1: Linux dump backup is used.
    • The sixth column indicates the fsck option, that is, whether to use fsck to check the attached disk during startup.
      • 0: not use fsck.
      • If the mount point is the root partition (/), this parameter must be set to 1.

        When this parameter is set to 1 for the root partition, this parameter for other partitions must start with 2 because the system checks the partitions in the ascending order of the values.

  5. Press Esc, enter :wq, and press Enter.

    The system saves the configurations and exits the vi editor.

  6. Perform the following operations to verify the automatic mounting function:

    1. Run the following command to unmount the partition:

      umount Disk partition

      In this example, run the following command:

      umount /dev/vdb1

    2. Run the following command to reload all the content in the /etc/fstab file:

      mount -a

    3. Run the following command to query the file system mounting information:

      mount | grep Mount point

      In this example, run the following command:

      mount | grep /mnt/sdc

      If information similar to the following is displayed, automatic mounting has been configured:

      root@ecs-test-0001 ~]# mount | grep /mnt/sdc
/dev/vdb1 on /mnt/sdc type ext4 (rw,relatime,data=ordered)