Help Center/ Elastic Volume Service/ User Guide (Kuala Lumpur Region)/ Disk Capacity Expansion/ Extending Disk Partitions and File Systems (Linux)/ Extending Partitions and File Systems for System Disks (Linux)

Updated on 2024-03-26 GMT+08:00

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Extending Partitions and File Systems for System Disks (Linux)

Scenarios

After a disk is 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.

If the disk capacity is expanded when its server is stopped, the additional space of a Linux system disk will be automatically added to the partition at the disk end upon the server startup. In this case, the additional space can be used directly.

This section uses CentOS 7.4 64bit and CentOS 6.5 64bit as the sample OSs to describe how to extend the disk partition using growpart and fdisk. 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.

For how to query the Linux kernel version, see Querying the Linux Kernel Version.

Extending an Existing MBR Partition (Kernel Version Later Than 3.6.0)
Extending an Existing MBR Partition (Kernel Version Earlier Than 3.6.0)
Creating a New MBR Partition

Performing the expansion operations with caution. Incorrect operations may lead to data loss or exceptions. So 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

You have expanded the disk capacity and attached the disk to a server on the management console. For details, see Expanding Capacity for an In-use EVS Disk or Expanding Capacity for an Available EVS Disk.
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.

Constraints

The additional space can only be added to the last partition of the disk.

Querying the Linux Kernel Version

Run the following command to query the Linux kernel version:

uname -a

Then, perform corresponding operations depending on whether the Linux kernel version is later than 3.6.0.

For CentOS 7.4 64bit, information similar to the following is displayed:
```
Linux ecs-test-0001 3.10.0-957.5.1.el7.x86_64 #1 SMP Fri Feb 1 14:54:57 UTC 2019 x86_64 x86_64 
```
The kernel version is 3.10.0, which is later than 3.6.0. For subsequent operations, see Extending an Existing MBR Partition (Kernel Version Later Than 3.6.0).
For CentOS 6.5 64bit, information similar to the following is displayed:
```
Linux ecs-test-0002 2.6.32-754.10.1.el6.x86_64 #1 SMP Tue Jan 15 17:07:28 UTC 2019 x86_64
```
The kernel version is 2.6.32, which is earlier than 3.6.0. In this case, the disk partition and file system extension take effect only after a server reboot. For subsequent operations, see Extending an Existing MBR Partition (Kernel Version Earlier Than 3.6.0).

Extending an Existing MBR Partition (Kernel Version Later Than 3.6.0)

CentOS 7.4 64bit is used as the sample OS. Originally, system disk /dev/vda has 40 GiB and one partition (/dev/vda1), and then 60 GiB is added to the disk. The following procedure shows you how to allocate the additional 60 GiB to the existing MBR partition /dev/vda1.

(Optional) Run the following command to install the growpart tool:

yum install cloud-utils-growpart

You can run growpart to check whether the growpart tool has been installed. If the command output displays the tool usage instructions, the tool has been installed and you do not need to install it again.

Run the following command to view the total capacity of the /dev/vda system disk:

fdisk -l

Information similar to the following is displayed:

[root@ecs-test-0001 ~]# fdisk -l

Disk /dev/vda: 107.4 GiB, 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: 0x000bcb4e

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

Run the following command to view the capacity of the /dev/vda1 partition:

df -TH

Information similar to the following is displayed:

[root@ecs-test-0001 ~]# df -TH
Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/vda1      ext4       43G  2.0G   39G   5% /
devtmpfs       devtmpfs  2.0G     0  2.0G   0% /dev
tmpfs          tmpfs     2.0G     0  2.0G   0% /dev/shm
tmpfs          tmpfs     2.0G  9.0M  2.0G   1% /run
tmpfs          tmpfs     2.0G     0  2.0G   0% /sys/fs/cgroup
tmpfs          tmpfs     398M     0  398M   0% /run/user/0

Run the following command to extend the partition using growpart:

growpart System disk Partition number

In this example, run the following command:

growpart /dev/vda 1
Information similar to the following is displayed:
```
[root@ecs-test-0001 ~]# growpart /dev/vda 1
CHANGED: partition=1 start=2048 old: size=83884032 end=83886080 new: size=209713119,end=209715167
```
Run the following command to extend the file system of the partition:

resize2fs Disk partition

In this example, run the following command:

resize2fs /dev/vda1
Information similar to the following is displayed:
```
[root@ecs-test-0001 ~]# resize2fs /dev/vda1
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/vda1 is mounted on /; on-line resizing required
old_desc_blocks = 5, new_desc_blocks = 13
The filesystem on /dev/vda1 is now 26214139 blocks long.
```
If the error message "open: No such file or directory while opening /dev/vdb1" is returned, an incorrect partition is specified. Run df -TH to view the disk partitions.

Run the following command to view the new capacity of the /dev/vda1 partition:

df -TH

Information similar to the following is displayed:

[root@ecs-test-0001 ~]# df -TH
Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/vda1      ext4      106G  2.0G   99G   2% /
devtmpfs       devtmpfs  2.0G     0  2.0G   0% /dev
tmpfs          tmpfs     2.0G     0  2.0G   0% /dev/shm
tmpfs          tmpfs     2.0G  9.0M  2.0G   1% /run
tmpfs          tmpfs     2.0G     0  2.0G   0% /sys/fs/cgroup
tmpfs          tmpfs     398M     0  398M   0% /run/user/0

Extending an Existing MBR Partition (Kernel Version Earlier Than 3.6.0)

If the OS kernel version is earlier than 3.6.0, the extension of an existing MBR disk partition and file system takes effect only after a server reboot, and services will be interrupted.

CentOS 6.5 64bit is used as the sample OS. Originally, system disk /dev/vda has 40 GiB and one partition (/dev/vda1), and then 60 GiB is added to the disk. The following procedure shows you how to allocate the additional 60 GiB to the existing MBR partition /dev/vda1.

(Optional) Run the following command to install the growpart tool:

yum install cloud-utils-growpart

You can run growpart to check whether the growpart tool has been installed. If the command output displays the tool usage instructions, the tool has been installed and you do not need to install it again.

Run the following command to install the dracut-modules-growroot tool:

yum install cloud-utils-growpart

Information similar to the following is displayed:

[root@ecs-test-0002 ~]# yum install cloud-utils-growpart
Loaded plugins: fastestmirror, security
Setting up Install Process
Determining fastest mirrors
...
Package cloud-utils-growpart-0.27-10.el6.x86_64 already installed and latest version
Nothing to do

Run the following command to regenerate the initramfs file:

dracut -f

Run the following command to view the total capacity of the /dev/vda system disk:

fdisk -l

Information similar to the following is displayed:

[root@ecs-test-0002 ~]# fdisk -l

Disk /dev/vda: 107.4 GiB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0004e0be

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *           1        5222    41942016   83  Linux

Run the following command to view the capacity of the /dev/vda1 partition:

df -TH

Information similar to the following is displayed:

[root@ecs-test-0002 ~]# df -TH
Filesystem     Type   Size  Used Avail Use% Mounted on
/dev/vda1      ext4    43G  1.7G   39G   5% /
tmpfs          tmpfs  2.1G     0  2.1G   0% /dev/shm

Run the following command to extend the partition using growpart:

growpart System disk Partition number

In this example, run the following command:

growpart /dev/vda 1
Information similar to the following is displayed:
```
[root@ecs-test-0002 ~]# growpart /dev/vda 1
CHANGED: partition=1 start=2048 old: size=83884032 end=83886080 new: size=209710462,end=209712510
```
Run the following command to restart the server:

reboot

After the server is restarted, reconnect to the server and perform the following steps.
Run the following command to extend the file system of the partition:

resize2fs Disk partition

In this example, run the following command:

resize2fs /dev/vda1
Information similar to the following is displayed:
```
[root@ecs-test-0002 ~]# resize2fs /dev/vda1
resize2fs 1.41.12 (17-May-2010)
The filesystem is already 26213807 blocks long.  Nothing to do!
```
If the error message "open: No such file or directory while opening /dev/vdb1" is returned, an incorrect partition is specified. Run df -TH to view the disk partitions.

Run the following command to view the new capacity of the /dev/vda1 partition:

df -TH

Information similar to the following is displayed:

[root@ecs-test-0002 ~]# df -TH
Filesystem     Type   Size  Used Avail Use% Mounted on
/dev/vda1      ext4   106G  1.7G   99G   2% /
tmpfs          tmpfs  2.1G     0  2.1G   0% /dev/shm

Creating a New MBR Partition

Originally, system disk /dev/vda has 40 GiB and one partition (/dev/vda1), and then 40 GiB is added to the disk. The following procedure shows you how to create a new MBR partition /dev/vda2 with this 40 GiB.

Run the following command to view the disk partition information:

fdisk -l

Information similar to the following is displayed:

[root@ecs-2220 ~]# fdisk -l

Disk /dev/vda: 85.9 GiB, 85899345920 bytes, 167772160 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: 0x0008d18f

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

In the command output, the capacity of the dev/vda system disk is 80 GiB, in which the in-use dev/vda1 partition takes 40 GiB and the additional 40 GiB has not been allocated.

Run the following command to enter fdisk:

fdisk /dev/vda

Information similar to the following is displayed:

[root@ecs-2220 ~]# fdisk /dev/vda
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):

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
```
There are two types of disk partitions:
- Choosing p creates a primary partition.
- Choosing e creates an extended partition.
If MBR is used, a maximum of 4 primary partitions, or 3 primary partitions plus 1 extended partition can be created. The extended partition must be divided into logical partitions before use.

Disk partitions created using GPT are not categorized.
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): 
```
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 (83886080-167772159, default 83886080):
```
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 (83886080-167772159, default 83886080):
Using default value 83886080
Last sector, +sectors or +size{K,M,G} (83886080-167772159,default 167772159):
```
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} (83886080-167772159,
default 167772159):
Using default value 167772159
Partition 2 of type Linux and of size 40 GiB is set

Command (m for help): 
```

Enter p and press Enter to view the new partition.

Information similar to the following is displayed:

Command (m for help): p

Disk /dev/vda: 85.9 GiB, 85899345920 bytes, 167772160 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: 0x0008d18f

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048    83886079    41942016   83  Linux
/dev/vda2        83886080   167772159    41943040   83  Linux
Command (m for help):

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.

The partition is created.

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

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

partprobe

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:

(The ext4 file system is used in this example.)

mkfs -t ext4 /dev/vda2

Information similar to the following is displayed:

[root@ecs-2220 ~]# mkfs -t ext4 /dev/vda2
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
2621440 inodes, 10485760 blocks
524288 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2157969408
320 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

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/vda2

Information similar to the following is displayed:

[root@ecs-2220 ~]# mkfs -t xfs /dev/vda2 
meta-data=/dev/vda2              isize=512     agcount=4, agsize=2621440 blks
         =                       sectsz=512    attr=2, projid32bit=1
         =                       crc=1         finobt=0, sparse=0
data     =                       bsize=4096    blocks=10485760, imaxpct=25
         =                       sunit=0       swidth=0 blks
naming   =version2               bsize=4096    ascii-ci=0 ftype=1
log      =internal log           bsize=4096    blocks=5120, 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.

(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 /opt mount point:

mkdir /opt
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/vda2 on /opt:

mount /dev/vda2 /opt

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.

Run the following command to view the mount result:

df -TH

Information similar to the following is displayed:

[root@ecs-2220 ~]# 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/vda2      ext4       43G   51M   40G   1% /opt

If the server is restarted, the mounting will become invalid. You can modify the /etc/fstab file to configure automount at startup. See the following part for details.

Configuring Automatic Mounting at System Start

The fstab file controls what disks are automatically mounted at server startup. You can configure the fstab file of a server that has data. This operation will not affect the existing data.

The following example uses UUIDs to identify disks in the fstab file. You are advised not to use device names (like /dev/vdb1) to identify disks in the file because device names are assigned dynamically and may change (for example, from /dev/vdb1 to /dev/vdb2) after a server stop or start. This can even prevent your server from booting up.

UUIDs are the unique character strings for identifying partitions in Linux.

Query the partition UUID.

blkid Disk partition

In this example, the UUID of the /dev/vdb1 partition is queried.

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"
```
Carefully record the UUID, as you will need it for the following step.
Open the fstab file using the vi editor.

vi /etc/fstab
Press i to enter editing mode.
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 information is used for reference only. The line starting with UUID is the information added. Edit this line from left to right to match the following format:
- UUID: The UUID obtained in 1.
- Mount point: The directory on which the partition is mounted. You can query the mount point using df -TH.
- Filesystem: The file system format of the partition. You can query the file system format using df -TH.
- Mount option: The partition mount option. Usually, this parameter is set to defaults.
- Dump: The Linux dump backup option.
  - 0: Linux dump backup is not used. Usually, dump backup is not used, and you can set this parameter to 0.
  - 1: Linux dump backup is used.
- fsck: The fsck option, which means whether to use fsck to check the disk during startup.
  - 0: not use fsck.
  - If the mount point is the root partition (/), this parameter must be set to 1.
    If 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.
Press Esc, enter :wq, and press Enter.

The system saves the configurations and exits the vi editor.
Verify that the disk is auto-mounted at startup.
1. Unmount the partition.
  umount Disk partition
  
  In this example, run the following command:
  
  umount /dev/vdb1
2. Reload all the content in the /etc/fstab file.
  mount -a
3. 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)

Previous topic: Partition and File System Extension Preparations (Linux)

Next topic: Extending Partitions and File Systems for Data Disks (Linux)

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