Performing Post-Expansion Operations for a Linux Disk (fdisk)
After the capacity expansion has succeeded, you need to allocate the extended space to an existing partition, or allocate new partitions to the expanded disks.
Prerequisites
- You have logged in to the BMS. For details, see section "Logging In to a Linux BMS" in Bare Metal Server User Guide.
- You have attached the EVS disk to the BMS and the additional disk space remains to be allocated.
Context
The OS used in the following example is CentOS 7.0 (64-bit).
The method for allocating the additional space varies depending on the server OS. This document is used for reference only. For the detailed operations and differences, see the corresponding OS documents.
- Create a partition (services will not be interrupted)
You can create a partition for the expanded disk without the need of detaching the original partitions. The impacts on services are smaller than expanding an existing partition. This method is recommended for system disks or disks carrying services that cannot be interrupted.
If the MBR partition style is used, the disk capacity cannot exceed 2 TB and the number of partitions cannot exceed the upper limit after the expansion completes.
- Expand an existing partition (services will be interrupted)
If the MBR partition style is used and the number of partitions has reached the upper limit, the existing partition needs to be expanded. Expanding an existing partition does not delete its data, but requires the partition to unmount. Therefore, the services will be interrupted.
If the MBR partition style is used and the disk capacity after expansion has exceeded 2 TB, the excessive disk space cannot be partitioned. In this case, if you change the partition style from MBR to GPT, the original disk data will be cleared. Therefore, back up the disk data before you change the partition style.
Viewing the Partition Style
Before allocating the additional space, query the current disk partition style. If MBR is used, you can use either the fdisk or Parted partitioning tool. If GPT is used, only the Parted partitioning tool can be used.
- Run the following command to view the current disk partition style:
fdisk -l
Information similar to the following is displayed:[root@ecs-1120 linux]# fdisk -l Disk /dev/xvda: 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: 0x000c5712 Device Boot Start End Blocks Id System /dev/xvda1 2048 83886079 41942016 83 Linux WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion. Disk /dev/xvdb: 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: gpt # Start End Size Type Name 1 34 209715166 100G Microsoft basic opt 2 209715167 314572766 50G Microsoft basic opt1 WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion. Disk /dev/xvdc: 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: gpt # Start End Size Type Name 1 34 16777215 8G Microsoft basic opt 2 16777216 83884031 32G Microsoft basic optIn the command output, parameter Disk label type indicates the disk partition style. Value dos indicates the MBR partition style, and value gpt indicates the GPT partition style.
Creating a Partition
The following example shows you how to create a partition for the expanded space of the system disk and mount the partition to /opt without interrupting services.
- Run the following command to view information about partitioning:
fdisk -l
Information similar to the following is displayed: (/dev/xvda is the system disk.)[root@ecs-bab9 test]# fdisk -l Disk /dev/xvda: 64.4 GB, 64424509440 bytes, 125829120 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: 0x000cc4ad Device Boot Start End Blocks Id System /dev/xvda1 * 2048 2050047 1024000 83 Linux /dev/xvda2 2050048 22530047 10240000 83 Linux /dev/xvda3 22530048 24578047 1024000 83 Linux /dev/xvda4 24578048 83886079 29654016 5 Extended /dev/xvda5 24580096 26628095 1024000 82 Linux swap / Solaris - Run the following command to enter fdisk (/dev/xvda is used in this example):
fdisk /dev/xvda
Information similar to the following is displayed:[root@ecs-bab9 test]# fdisk /dev/xvda 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 partition.
Because the system disk has five existing partitions, the system automatically creates the sixth one.
Information similar to the following is displayed:Command (m for help): n All primary partitions are in use Adding logical partition 6 First sector (26630144-83886079, default 26630144):
- Enter the new partition's first sector number, for example the default value, and press Enter.
The serial number of first sector must be greater than that of the last sector of the existing partition.
Information similar to the following is displayed:First sector (26630144-83886079, default 26630144): Using default value 26630144 Last sector, +sectors or +size{K,M,G} (26630144-83886079, default 83886079): - Enter the new partition's last sector number and press Enter.
The default last sector is used in this example.
Information similar to the following is displayed:Last sector, +sectors or +size{K,M,G} (26630144-83886079, default 83886079): Using default value 83886079 Partition 6 of type Linux and of size 27.3 GiB is set Command (m for help): - Enter p and press Enter to view the created partition.
Information similar to the following is displayed:
Disk /dev/xvda: 64.4 GB, 64424509440 bytes, 125829120 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: 0x000cc4ad Device Boot Start End Blocks Id System /dev/xvda1 * 2048 2050047 1024000 83 Linux /dev/xvda2 2050048 22530047 10240000 83 Linux /dev/xvda3 22530048 24578047 1024000 83 Linux /dev/xvda4 24578048 83886079 29654016 5 Extended /dev/xvda5 24580096 26628095 1024000 82 Linux swap / Solaris /dev/xvda6 26630144 83886079 28627968 83 Linux Command (m for help): - Enter w and press Enter to write the changes into 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 successfully 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 of the new partition:
In this example, the ext4 file system is used.
mkfs -t ext4 /dev/xvda6
Information similar to the following is displayed:[root@ecs-bab9 test]# mkfs -t ext4 /dev/xvda6 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 1790544 inodes, 7156992 blocks 357849 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=2155872256 219 block groups 32768 blocks per group, 32768 fragments per group 8176 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000 Allocating group tables: done Writing inode tables: done Creating journal (32768 blocks): done Writing superblocks and filesystem accounting information: doneThe formatting takes a while. When done is displayed in the command output, the formatting is complete.
- Run the following command to mount the new partition on the space-demanding directory, for example /opt:
mount /dev/xvda6 /opt
Information similar to the following is displayed:[root@ecs-bab9 test]# mount /dev/xvda6 /opt [root@ecs-bab9 test]#
If the new partition is mounted to a directory that is not empty, the subdirectories and files in the directory will be hidden. In this situation, you are advised to mount the new partition to an empty directory or a new directory. If the new partition must be mounted to 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 check the mounting result:
df -TH
Information similar to the following is displayed:[root@ecs-bab9 test]# df -TH Filesystem Type Size Used Avail Use% Mounted on /dev/xvda2 xfs 11G 7.4G 3.2G 71% / devtmpfs devtmpfs 4.1G 0 4.1G 0% /dev tmpfs tmpfs 4.1G 82k 4.1G 1% /dev/shm tmpfs tmpfs 4.1G 9.2M 4.1G 1% /run tmpfs tmpfs 4.1G 0 4.1G 0% /sys/fs/cgroup /dev/xvda3 xfs 1.1G 39M 1.1G 4% /home /dev/xvda1 xfs 1.1G 131M 915M 13% /boot /dev/xvda6 ext4 29G 47M 28G 1% /opt
Replacing the Existing Partition
In the following example, a disk has been attached to the BMS, and the partition /dev/xvdb1 has been mounted to /mnt/sdc. During the process of replacing the original partition /dev/xvdb1 and adding new capacity to it, services will be interrupted.
After the disk capacity has been expanded, the additional space is added to the end of the disk. When the disk has multiple partitions, only the partition at the end of the disk can be expanded.
- Run the following command to view information about partitioning:
fdisk -l
Information similar to the following is displayed:[root@ecs-b656 test]# fdisk -l Disk /dev/xvda: 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: 0x000cc4ad Device Boot Start End Blocks Id System /dev/xvda1 * 2048 2050047 1024000 83 Linux /dev/xvda2 2050048 22530047 10240000 83 Linux /dev/xvda3 22530048 24578047 1024000 83 Linux /dev/xvda4 24578048 83886079 29654016 5 Extended /dev/xvda5 24580096 26628095 1024000 82 Linux swap / Solaris Disk /dev/xvdb: 21.5 GB, 21474836480 bytes, 41943040 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: 0xb00005bd Device Boot Start End Blocks Id System /dev/xvdb1 2048 20971519 10484736 83 LinuxIn the command output, the total capacity of the /dev/xvdb disk is 21.5 GB, and the disk has only one partition, dev/xvdb1. The partition's first sector is 2048, and its last sector is 20971519.
View the /dev/xvdb capacity and check whether the additional space is included.- If the additional space is not included, refresh the capacity according to section Performing Post-Expansion Operations for a SLES Disk (fdisk).
- If the additional space is included, take note of the first and last sectors of the dev/xvdb1 partition and then go to 2. These values will be used in the follow-up operations.
- Run the following command to unmount the disk partition:
umount /mnt/sdc
- Run the following command to enter fdisk and enter d to delete the /dev/xvdb1 partition:
fdisk /dev/xvdb
The command output is as follows:[root@ecs-b656 test]# fdisk /dev/xvdb 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): d Selected partition 1 Partition 1 is deleted Command (m for help):
If the partitions are recreated according to the following steps, deleting partitions will not cause data loss on the data disk.
- Enter n and press Enter to create a partition.
To create a partition, enter n.
Information similar to the following is displayed:Command (m for help): n Partition type: p primary (0 primary, 0 extended, 4 free) e extended
There are two types of disk partition:- p indicates a primary partition.
- e indicates an extended partition.
- Ensure that the entered partition type is the same as the original partition type, which is the primary partition in this example. Enter p and press Enter to create a primary partition.
Information similar to the following is displayed:
Select (default p): p Partition number (1-4, default 1):
In the command output, Partition number specifies the serial number of the primary partition.
- Ensure that the serial number you entered is the same as the original partition's, which is 1 in this example. Enter 1 and press Enter.
Information similar to the following is displayed:
Partition number (1-4, default 1): 1 First sector (2048-41943039, default 2048):
In the command output, First sector specifies the first sector.
Data will be lost if:- The first sector you selected is inconsistent with the original partition.
- The last sector you selected is smaller than that of the original partition.
- Ensure that the entered first sector is the same as that of the original partition. In this example, first sector 2048 is recorded in 1. Enter 2048 and press Enter.
Information similar to the following is displayed:
First sector (2048-41943039, default 2048): Using default value 2048 Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039):In the command output, Last sector specifies the last sector.
- Ensure that the entered last sector is equal to or larger than the last sector recorded in 1. In this example, the recorded last sector is 20971519, and the default last sector 41943039 is used. Enter 41943039 and press Enter.
Information similar to the following is displayed:
Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): Using default value 41943039 Partition 1 of type Linux and of size 20 GiB is set Command (m for help):The primary partition is successfully created.
- Enter p and press Enter to view the details about the created partition.
Information similar to the following is displayed:
Command (m for help): p Disk /dev/xvdb: 21.5 GB, 21474836480 bytes, 41943040 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: 0xb00005bd Device Boot Start End Blocks Id System /dev/xvdb1 2048 41943039 20970496 83 Linux Command (m for help):Details about the /dev/xvdb1 partition are displayed.
- Enter w and press Enter to write the changes into 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. Syncing disks.
The partition is successfully created.
In case that you want to discard the changes made before, you can exit fdisk by entering q.
- Run the following command to check the correctness of the file system on /dev/xvdb1:
e2fsck -f /dev/xvdb1
Information similar to the following is displayed:[root@ecs-b656 test]# e2fsck -f /dev/xvdb1 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/xvdb1: 11/655360 files (0.0% non-contiguous), 83137/2621184 blocks
- Run the following command to expand the size of the file system on /dev/xvdb1:
resize2fs /dev/xvdb1
Information similar to the following is displayed:[root@ecs-b656 test]# resize2fs /dev/xvdb1 resize2fs 1.42.9 (28-Dec-2013) Resizing the filesystem on /dev/xvdb1 to 5242624 (4k) blocks. The filesystem on /dev/xvdb1 is now 5242624 blocks long.
- Run the following command to mount the created partition to the /mnt/sdc directory:
mount /dev/xvdb1 /mnt/sdc
- Run the following command to view the mounting result of /dev/xvdb2:
df -TH
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