Extending Partitions and File Systems for SCSI Disks (Linux)

Scenarios

After a disk has been expanded on the management console, the disk size is enlarged, but the additional space cannot be used directly.

In Linux, you must allocate the additional space to an existing partition or a new partition.

This section uses CentOS 7.4 64bit as the sample OS to describe how to extend an MBR partition of a SCSI data disk. The method for allocating the additional space varies with the server OS. This section is used for reference only. For detailed operations and differences, see the corresponding OS documents.

Performing the expansion operations with caution. Misoperation may lead to data loss or exceptions. Therefore, you are advised to back up the disk data using CBR or snapshots before expansion. For details about using CBR, see Managing EVS Backups. For details about using snapshots, see Creating a Snapshot.

Prerequisites

Creating a New MBR Partition

Originally, data disk /dev/sda has 50 GiB and one partition (/dev/sda1), and then 50 GiB is added to the disk. The following procedure shows you how to create a new MBR partition /dev/sda2 with this 50 GiB.

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

    fdisk -l

    Information similar to the following is displayed:
    [root@ecs-scsi ~]# fdisk -l

Disk /dev/vda: 42.9 GB, 42949672960 bytes, 83886080 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000bcb4e

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048    83886079    41942016   83  Linux

Disk /dev/sda: 107.4 GB, 107374182400 bytes, 209715200 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x915ffe6a

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048   104857599    52427776   83  Linux
    View the /dev/sda capacity and check whether the additional space is included.
    • If the additional space is not included, refresh the capacity according to 2.
    • If the additional space is included, go to 3.

  2. (Optional) Run the following command to update the capacity of the SCSI data disk:

    1. Run the following command to update the disk capacity on the server:

      echo 1 > /sys/class/scsi_device/%d:%d:%d:%d/device/rescan &

      In the command, %d:%d:%d:%d indicates a folder in the /sys/class/scsi_device/ directory and can be obtained using ll /sys/class/scsi_device/.

      Information similar to the following is displayed: (2:0:0:0 indicates the folder to be obtained.)
      cs-xen-02:/sys/class/scsi_device # ll /sys/class/scsi_device/
total 0
lrwxrwxrwx 1 root root 0 Sep 26 11:37 2:0:0:0 -> ../../devices/xen/vscsi-2064/host2/target2:0:0/2:0:0:0/scsi_device/2:0:0:0

      In this example, run the following command:

      echo 1 > /sys/class/scsi_device/2:0:0:0/device/rescan &

    2. After the disk capacity is updated, run the following command to view the disk partition information again:

      fdisk -l

      If the additional space is included, go to 3.

  3. Run the following command to enter fdisk:

    fdisk Disk

    In this example, run the following command:

    fdisk /dev/sda

    Information similar to the following is displayed:
    [root@ecs-scsi ~]# fdisk /dev/sda
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help):

  4. Enter n and press Enter to create a new partition.

    Information similar to the following is displayed:
    Command (m for help): n
Partition type:
   p   primary (1 primary, 0 extended, 3 free)
   e   extended
Select (default p):
    There are two types of disk partitions:
    • Choosing p creates a primary partition.
    • Choosing e creates an extended partition.

    If the MBR partition style is used, a maximum of 4 primary partitions, or 3 primary partitions and 1 extended partition can be created. The extended partition cannot be used directly and must be divided into logical partitions before use.

    Disk partitions created using GPT are not categorized.

  5. In this example, a primary partition is created. Therefore, enter p and press Enter to create a primary partition.

    Information similar to the following is displayed:
    Select (default p): p
Partition number (2-4, default 2):

    Partition number indicates the serial number of the primary partition. Because partition number 1 has been used, the value ranges from 2 to 4.

  6. Enter the serial number of the primary partition and press Enter. Partition number 2 is used in this example. Therefore, enter 2 and press Enter.

    Information similar to the following is displayed:
    Partition number (2-4, default 2): 2
First sector (104857600-209715199, default 104857600):

    First sector indicates the start sector. The value ranges from 104857600 to 209715199, and the default value is 104857600.

  7. Enter the new partition's start sector and press Enter. In this example, the default start sector is used.

    The system displays the start and end sectors of the partition's available space. You can customize the value within this range or use the default value. The start sector must be smaller than the partition's end sector.

    Information similar to the following is displayed:
    First sector (104857600-209715199, default 104857600):
Using default value 104857600
Last sector, +sectors or +size{K,M,G} (104857600-209715199, default 209715199):

    Last sector indicates the end sector. The value ranges from 104857600 to 209715199, and the default value is 209715199.

  8. Enter the new partition's end sector and press Enter. In this example, the default end sector is used.

    The system displays the start and end sectors of the partition's available space. You can customize the value within this range or use the default value. The start sector must be smaller than the partition's end sector.

    Information similar to the following is displayed:
    Last sector, +sectors or +size{K,M,G} (104857600-209715199, default 209715199):
Using default value 209715199
Partition 2 of type Linux and of size 50 GiB is set

Command (m for help):

  9. Enter p and press Enter to view the new partition.

    Information similar to the following is displayed:
    Command (m for help): p

Disk /dev/sda: 107.4 GB, 107374182400 bytes, 209715200 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x915ffe6a

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048   104857599    52427776   83  Linux
/dev/sda2       104857600   209715199    52428800   83  Linux

Command (m for help):

  10. Enter w and press Enter to write the changes to the partition table.

    Information similar to the following is displayed:
    Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

    In case that you want to discard the changes made before, you can exit fdisk by entering q.

  11. Run the following command to synchronize the new partition table to the OS:

    partprobe

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

    mkfs -t File system Disk partition

    • Sample command of the ext* file system:

      mkfs -t ext4 /dev/sda2

      Information similar to the following is displayed:
      [root@ecs-scsi ~]# mkfs -t ext4 /dev/sda2
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
3276800 inodes, 13107200 blocks
655360 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2162163712
400 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

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
    • Sample command of the xfs file system:

      mkfs -t xfs /dev/sda2

      Information similar to the following is displayed:

      [root@ecs-scsi ~]# mkfs -t xfs /dev/sda2
meta-data=/dev/sda2              isize=512     agcount=4, agsize=3276800 blks
         =                       sectsz=512    attr=2, projid32bit=1
         =                       crc=1         finobt=0, sparse=0
data     =                       bsize=4096    blocks=13107200, imaxpct=25
         =                       sunit=0       swidth=0 blks
naming   =version2               bsize=4096    ascii-ci=0 ftype=1
log      =internal log           bsize=4096    blocks=6400, version=2
         =                       sectsz=512    sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096    blocks=0, rtextents=0

    The formatting takes a while, and you need to observe the system running status. Once done is displayed in the command output, the formatting is complete.

  13. (Optional) Run the following command to create a mount point:

    Perform this step if you want to mount the partition on a new mount point.

    mkdir Mount point

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

    mkdir /mnt/test

  14. Run the following command to mount the new partition:

    mount Disk partition Mount point

    In this example, run the following command to mount the new partition /dev/sda2 on /mnt/test:

    mount /dev/sda2 /mnt/test

    If the new partition is mounted on a directory that is not empty, the subdirectories and files in the directory will be hidden. Therefore, you are advised to mount the new partition on an empty directory or a new directory. If the new partition must be mounted on a directory that is not empty, move the subdirectories and files in this directory to another directory temporarily. After the partition is successfully mounted, move the subdirectories and files back.

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

    df -TH

    Information similar to the following is displayed:
    [root@ecs-scsi ~]# df -TH
Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/vda1      ext4       43G  2.0G   39G   5% /
devtmpfs       devtmpfs  509M     0  509M   0% /dev
tmpfs          tmpfs     520M     0  520M   0% /dev/shm
tmpfs          tmpfs     520M  7.2M  513M   2% /run
tmpfs          tmpfs     520M     0  520M   0% /sys/fs/cgroup
tmpfs          tmpfs     104M     0  104M   0% /run/user/0
/dev/sda1      ext4       53G   55M   50G   1% /mnt/sdc
/dev/sda2      ext4       53G   55M   50G   1% /mnt/test

    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.

Extending an Existing MBR Partition

If the additional space is allocated to an existing partition, data on the disk will not be cleared but you must use umount to unmount the existing partition. In this case, services will be affected.

Originally, SCSI data disk /dev/sda has 100 GiB and two partitions (/dev/sda1 and /dev/sda2), and then 50 GiB is added to the disk. The following procedure shows you how to add this 50 GiB to the existing MBR partition /dev/sda2.

During an expansion, the additional space is added to the end of the disk. Therefore, if the disk has multiple partitions, the additional space can only be allocated to the partition at the disk end.

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

    fdisk -l

    Information similar to the following is displayed:
    [root@ecs-scsi ~]# fdisk -l

Disk /dev/vda: 42.9 GB, 42949672960 bytes, 83886080 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000bcb4e

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048    83886079    41942016   83  Linux

Disk /dev/sda: 161.1 GB, 161061273600 bytes, 314572800 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x915ffe6a

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048   104857599    52427776   83  Linux
/dev/sda2       104857600   209715199    52428800   83  Linux

    In the command output, take note of the partition's start and end sectors. In this example, /dev/sda2's start sector is 104857600, and its end sector is 209715199.

    View the /dev/sda capacity and check whether the additional space is included.
    • If the additional space is not included, refresh the capacity according to 2.
    • If the additional space is included, take note of the start and end sectors of the target partition and then go to 3. These values will be used in the subsequent operations.

  2. (Optional) Run the following command to update the capacity of the SCSI data disk:

    1. Run the following command to update the disk capacity on the server:

      echo 1 > /sys/class/scsi_device/%d:%d:%d:%d/device/rescan &

      In the command, %d:%d:%d:%d indicates a folder in the /sys/class/scsi_device/ directory and can be obtained using ll /sys/class/scsi_device/.

      Information similar to the following is displayed: (2:0:0:0 indicates the folder to be obtained.)
      cs-xen-02:/sys/class/scsi_device # ll /sys/class/scsi_device/
total 0
lrwxrwxrwx 1 root root 0 Sep 26 11:37 2:0:0:0 -> ../../devices/xen/vscsi-2064/host2/target2:0:0/2:0:0:0/scsi_device/2:0:0:0

      In this example, run the following command:

      echo 1 > /sys/class/scsi_device/2:0:0:0/device/rescan &

    2. After the disk capacity is updated, run the following command to view the disk partition information again:

      fdisk -l

      If the additional space is included, take note of the start and end sectors of the target partition and then go to 3. These values will be used in the subsequent operations.

  3. Run the following command to unmount the partition:

    umount Disk partition

    In this example, run the following command:

    umount /dev/sda2

  4. Run the following command to enter fdisk:

    fdisk Disk

    In this example, run the following command:

    fdisk /dev/sda

    Information similar to the following is displayed:
    [root@ecs-scsi ~]# fdisk /dev/sda
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help):

  5. Run the following command to delete the partition to be extended:

    1. Enter d and press Enter to delete the partition.
      Information similar to the following is displayed:
      Command (m for help): d
Partition number (1,2, default 2):
    2. Enter the partition number and press Enter to delete the partition. In this example, enter 2.
      Information similar to the following is displayed:
      Partition number (1,2, default 2): 2
Partition 2 is deleted

Command (m for help):

      After deleting the partition, recreate the partition according to the following steps, and data on this disk will not be lost.

  6. Enter n and press Enter to create a new partition.

    Information similar to the following is displayed:
    Command (m for help): n
Partition type:
   p   primary (1 primary, 0 extended, 3 free)
   e   extended
Select (default p):
    There are two types of disk partitions:
    • Choosing p creates a primary partition.
    • Choosing e creates an extended partition.

    If the MBR partition style is used, a maximum of 4 primary partitions, or 3 primary partitions and 1 extended partition can be created. The extended partition cannot be used directly and must be divided into logical partitions before use.

    Disk partitions created using GPT are not categorized.

  7. Ensure that the entered partition type is the same as the partition had before. In this example, a primary partition is used. Therefore, enter p and press Enter to create a primary partition.

    Information similar to the following is displayed:
    Select (default p): p
Partition number (2-4, default 2):

    Partition number indicates the serial number of the primary partition.

  8. Ensure that entered partition number is the same as the partition had before. In this example, partition number 2 is used. Therefore, enter 2 and press Enter.

    Information similar to the following is displayed:
    Partition number (2-4, default 2): 2
First sector (104857600-314572799, default 104857600):

    In the command output, First sector specifies the start sector.

    Data will be lost if the following operations are performed:
    • Select a start sector other than the partition had before.
    • Select an end sector smaller than the partition had before.

  9. Ensure that the entered start sector is the same as the partition had before. In this example, start sector 104857600 is recorded in 1 or 2. Therefore, enter 104857600 and press Enter.

    Information similar to the following is displayed:
    First sector (104857600-314572799, default 104857600):
Using default value 104857600
Last sector, +sectors or +size{K,M,G} (104857600-314572799, default 314572799):

    In the command output, Last sector specifies the end sector.

  10. Ensure that the entered end sector is larger than or equal to the end sector recorded in 1 or 2. In this example, the recorded end sector is 209715199, and the default end sector is used. Therefore, enter 314572799 and press Enter.

    Information similar to the following is displayed:
    Last sector, +sectors or +size{K,M,G} (104857600-314572799, default 314572799):
Using default value 314572799
Partition 2 of type Linux and of size 100 GiB is set

Command (m for help):

    The partition is created.

  11. Enter p and press Enter to view the partition details.

    Information similar to the following is displayed:

    Command (m for help): p

Disk /dev/sda: 161.1 GB, 161061273600 bytes, 314572800 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x915ffe6a

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048   104857599    52427776   83  Linux
/dev/sda2       104857600   314572799    104857600  83  Linux

Command (m for help):

  12. Enter w and press Enter to write the changes to the partition table.

    Information similar to the following is displayed: (The partition is successfully created.)
    Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

    In case that you want to discard the changes made before, you can exit fdisk by entering q.

  13. Run the following command to synchronize the new partition table to the OS:

    partprobe

  14. Perform the following operations based on the file system of the disk:

    • For the ext* file system
      1. Run the following command to check the correctness of the file system on the partition:

        e2fsck -f Disk partition

        In this example, run the following command:

        e2fsck -f /dev/sda2

        Information similar to the following is displayed:
        [root@ecs-scsi ~]# e2fsck -f /dev/sda2
e2fsck 1.42.9 (28-Dec-2013)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/sda2: 11/3276800 files (0.0% non-contiguous), 251790/13107200 blocks
      2. Run the following command to extend the file system of the partition:

        resize2fs Disk partition

        In this example, run the following command:

        resize2fs /dev/sda2

        Information similar to the following is displayed:
        [root@ecs-scsi ~]# resize2fs /dev/sda2
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/sda2 to 26214400 (4k) blocks.
The filesystem on /dev/sda2 is now 26214400 blocks long.
      3. (Optional) Run the following command to create a mount point:

        Perform this step if you want to mount the partition on a new mount point.

        mkdir Mount point

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

        mkdir /mnt/test

      4. Run the following command to mount the partition:

        mount Disk partition Mount point

        In this example, run the following command to mount partition /dev/sda2 on /mnt/test:

        mount /dev/sda2 /mnt/test

        If the new partition is mounted on a directory that is not empty, the subdirectories and files in the directory will be hidden. Therefore, you are advised to mount the new partition on an empty directory or a new directory. If the new partition must be mounted on a directory that is not empty, move the subdirectories and files in this directory to another directory temporarily. After the partition is successfully mounted, move the subdirectories and files back.

    • For the xfs file system
      1. (Optional) Run the following command to create a mount point:

        Perform this step if you want to mount the partition on a new mount point.

        mkdir Mount point

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

        mkdir /mnt/test

      2. Run the following command to mount the partition:

        mount Disk partition Mount point

        In this example, run the following command to mount partition /dev/sda2 on /mnt/test:

        mount /dev/sda2 /mnt/test

        If the new partition is mounted on a directory that is not empty, the subdirectories and files in the directory will be hidden. Therefore, you are advised to mount the new partition on an empty directory or a new directory. If the new partition must be mounted on a directory that is not empty, move the subdirectories and files in this directory to another directory temporarily. After the partition is successfully mounted, move the subdirectories and files back.

      3. Run the following command to extend the file system of the partition:

        sudo xfs_growfs Disk partition

        In this example, run the following command:

        sudo xfs_growfs /dev/sda2

        Information similar to the following is displayed:

        [root@ecs-scsi ~]# sudo xfs_growfs /dev/sda2
meta-data=/dev/sda2              isize=512     agcount=4, agsize=3276800 blks
         =                       sectsz=512    attr=2, projid32bit=1
         =                       crc=1         finobt=0, spinodes=0
data     =                       bsize=4096    blocks=13107200, imaxpct=25
         =                       sunit=0       swidth=0 blks
naming   =version2               bsize=4096    ascii-ci=0 ftype=1
log      =internal               bsize=4096    blocks=6400, version=2
         =                       sectsz=512    sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096    blocks=0, rtextents=0
data blocks changed from 13107200 to 26214400df .

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

    df -TH

    Information similar to the following is displayed:

    [root@ecs-scsi ~]# df -TH
Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/vda1      ext4       43G  2.0G   39G   5% /
devtmpfs       devtmpfs  509M     0  509M   0% /dev
tmpfs          tmpfs     520M     0  520M   0% /dev/shm
tmpfs          tmpfs     520M  7.2M  513M   2% /run
tmpfs          tmpfs     520M     0  520M   0% /sys/fs/cgroup
tmpfs          tmpfs     104M     0  104M   0% /run/user/0
/dev/sda1      ext4       53G   55M   50G   1% /mnt/sdc
/dev/sda2      ext4      106G   63M  101G   1% /mnt/test

    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

  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)

Parent topic: Extending Disk Partitions and File Systems (Linux)