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 fdisk partitioning tool is suitable only for MBR partitions, and the parted partitioning tool is suitable for both MBR and GPT partitions. For more information, see Scenarios and Disk Partitions.
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.
Important
When using a disk for the first time, if you have not initialized it, including creating partitions and file systems, the additional space added to this disk in an expansion later may not be normally used.
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.
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.
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.
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)
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: 107GiB 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.
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
Important
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.
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: 107GiB 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.
Enter unit s and press Enter to set the measurement unit of the disk to sector.
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. Value 2048s indicates the disk start sector, and 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)
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)
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.
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.
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.
Important
The partition sizes supported by file systems vary. Therefore, you are advised to choose an appropriate file system based on your service requirements.
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
Note
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.
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
Run the following command to view the mount result:
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 1.9G 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 /dev/vdb1 ext4 106G 63M 101G 1% /mnt/sdc
New partition /dev/vdb1 is mounted on /mnt/sdc.
Note
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.
Note
UUID is the unique character string for disk partitions in a Linux system.
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.
Run the following command to 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 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.
Press Esc, enter :wq, and press Enter.
The system saves the configurations and exits the vi editor.
Perform the following operations to verify the automatic mounting function:
Run the following command to unmount the partition:
umount Disk partition
In this example, run the following command:
umount /dev/vdb1
Run the following command to reload all the content in the /etc/fstab file:
mount -a
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)