Help Center/ Dedicated Enterprise Storage Service/ User Guide/ Quick Start/ Initializing a Data Disk/ Initializing a Linux Data Disk (Using Parted)
Updated on 2022-02-22 GMT+08:00
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Initializing a Linux Data Disk (Using Parted)

Scenarios

This section uses CentOS 7.0 64-bit as an example to describe how to initialize a data disk attached to a Linux BMS and use Parted to partition the data disk.

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

Prerequisites

  • You have logged in to the BMS as user root. For details, see section "Logging In to a Linux BMS" in Bare Metal Server User Guide.
  • A data disk has been attached to the BMS and has not been initialized.

Creating Partitions and Mounting a Disk

The following example shows you how to use Parted to create a partition on a new data disk that has been attached to the BMS. The default partitioning style is GPT and the default file system format is ext4. Mount the file system to /mnt/sdc, and configure automatic mounting upon system start.

  1. Run the following command to view information about the added disk:

    lsblk

    Information similar to the following is displayed:

    [root@ecs-centos-70 linux]# lsblk
NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
xvda    202:0    0   40G  0 disk 
├─xvda1 202:1    0    4G  0 part [SWAP]
└─xvda2 202:2    0   36G  0 part /
xvdb    202:16   0  10G  0 disk

    This command output indicates that the BMS contains two disks. /dev/xvda is used as the system disk, and /dev/xvdb is the newly added data disk.

  2. Run the following command to use Parted to partition the added data disk:

    parted Added data disk

    In this example, /dev/xvdb is the added data disk.

    parted /dev/xvdb

    Information similar to the following is displayed:

    [root@ecs-centos-70 linux]# parted /dev/xvdb
GNU Parted 3.1
Using /dev/xvdb
Welcome to GNU Parted! Type 'help' to view a list of commands.

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

    Information similar to the following is displayed:

    (parted) p
Error: /dev/xvdb: unrecognised disk label
Model: Xen Virtual Block Device (xvd)                                     
Disk /dev/xvdb: 10.7GB
Sector size (logical/physical): 512B/512B
Partition Table: unknown
Disk Flags:

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

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

    mklabel Disk partition style

    For example, run the following command to set the partition style to GPT: (The disk partition styles include MBR and GPT.)

    mklabel gpt

    If you change the disk partition style after the disk has been used, the original data on the disk will be cleared. Therefore, select a proper disk partition style when initializing the disk.

  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: Xen Virtual Block Device (xvd)
Disk /dev/xvdb: 20971520s
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start  End  Size  File system  Name  Flags

  6. Enter unit s and press Enter to set the measurement unit of the disk to sector numbers.
  7. Enter mkpart opt 2048s 100% and press Enter. In this example, one partition is created for the added data disk.

    2048s indicates the initial disk capacity, and 100%indicates the final disk capacity. You can determine the number of partitions and the partition capacity based on your service requirements.

    Information similar to the following is displayed: 
    (parted) mkpart opt 2048s 100%
Warning: The resulting partition is not properly aligned for best performance.
Ignore/Cancel? Cancel

    If the preceding warning message is displayed, enter Cancel to stop partitioning. Then, find the first sector with the best disk performance and use that value to partition the disk. In this example, the first sector with the best disk performance is 2048s. Therefore, the system does not display the warning message.

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

    Information similar to the following is displayed:

    (parted) p                                                                
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvdb: 20971520s
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End        Size       File system  Name  Flags
 1      2048s   20969471s  20967424s               opt

    Details about the /dev/xvdb1 partition are displayed.

  9. Enter q and press Enter to exit Parted.
  10. Run the following command to view information about partitioning:

    lsblk

    Information similar to the following is displayed:

    [root@ecs-centos-70 linux]# lsblk                                 
NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
xvda    202:0    0   40G  0 disk 
├─xvda1 202:1    0    4G  0 part [SWAP]
└─xvda2 202:2    0   36G  0 part /
xvdb    202:16   0  100G  0 disk 
└─xvdb1 202:17   0  100G  0 part

    In the command output, /dev/xvdb1 is the partition you created.

  11. Run the following command to set the file system format of the created partition:

    mkfs -t File system format /dev/xvdb1

    For example, run the following command to set the file system format to ext4:

    mkfs -t ext4 /dev/xvdb1

    Information similar to the following is displayed:

    [root@ecs-centos-70 linux]# mkfs -t ext4 /dev/xvdb1
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
655360 inodes, 2620928 blocks
131046 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2151677925
80 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

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. Wait for the system running, 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 mounting point:

    mkdir Mounting point

    For example, run the following command to create a mounting point /mnt/sdc:

    mkdir /mnt/sdc

  13. Run the following command to mount the new partition to the mounting point created in 12.

    mount /dev/xvdb1 Mounting point

    For example, run the following command to mount the created partition to /mnt/sdc:

    mount /dev/xvdb1 /mnt/sdc

  14. Run the following command to check the mounting result:

    df -TH

    Information similar to the following is displayed:

    [root@ecs-centos-70 linux]# df -TH
Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/xvda2     xfs        39G  4.0G   35G  11% /
devtmpfs       devtmpfs  946M     0  946M   0% /dev
tmpfs          tmpfs     954M     0  954M   0% /dev/shm
tmpfs          tmpfs     954M  9.1M  945M   1% /run
tmpfs          tmpfs     954M     0  954M   0% /sys/fs/cgroup
/dev/xvdb1     ext4      11G   38M  101G   1% /mnt/sdc

    The new partition /dev/xvdb1 is mounted to /mnt/sdc.

Setting Automatic Disk Mounting at System Start

To automatically mount a disk when a BMS starts, you should not specify its partition, for example /dev/xvdb1, in /etc/fstab. This is because the sequence of cloud devices may change during the BMS stop and start. For example, /dev/xvdb1 may change to /dev/xvdb2. You are advised to use the UUID to automatically mount data disks.

The 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

    For example, run the following command to query the UUID of /dev/xvdb1:

    blkid /dev/xvdb1

    Information similar to the following is displayed:

    [root@ecs-b656 test]# blkid /dev/xvdb1
/dev/xvdb1: UUID="1851e23f-1c57-40ab-86bb-5fc5fc606ffa" TYPE="ext4"

    The UUID of /dev/xvdb1 is displayed.

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

    vi /etc/fstab

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

    UUID=1851e23f-1c57-40ab-86bb-5fc5fc606ffa /mnt/sdc      ext4 defaults     0   2

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

    The system saves the configurations and exits the vi editor.

Parent topic: Initializing a Data Disk