Resize the Root Volume

ZStack Cloud allows you to resize the root volume of a VM instance when the VM instance is in the running or stopped state. Note that only increasing volume size is supported.

Resize the Root Volume

You can resize the root volume of a VM instance by using one of the following methods:
  1. On the VM Instance management page, select a VM instance that is in the running or stopped state and choose Actions > System Configurations > Resize Root Volume. Then, the Resize Root Volume dialog box is displayed.
    You can set a new size as needed. The new size takes effect immediately.
    Figure 1. Resize Root Volume


  2. Select a VM instance that is in the running or stopped state and go to the details page of the VM instance. On the Configuration Info tab page, select the root volume to be resized and choose Actions > Resize Volume. Then, the Resize Volume dialog box is displayed.
    You can set a new size as needed. The new size takes effect immediately.
    Figure 2. Resize Volume


  3. Select a VM instance that is in the running or stopped state and go to the details page of the VM instance. On the Configuration Info tab page, click on the name of the root volume to be resized and set a new size for the root volume. The new size takes effect immediately.

The steps above only increase the size of the root volume. To make the new size recognized by the VM instance, partition and resize the hard disk in the operating system of the VM instance.

Partition and Resize the Hard Disk

The resize method varies according to the VM type, partition, and file system.
Note:
  • Before you resize a root volume, create a snapshot for the VM instance to enhance the data security.
  • The resize operation has potential risks. For security reasons, we recommend that you plan a new partition for the new size.
  • The resize operation only increases the size, not reduce the size.
  • The increased size can be merged into the last partition for continuous use.
    • If the last partition is a system backup partition (Windows), you must plan a new partition for the increased size.
    • If the last partition is a swap partition, you can delete the swap partition first, add the increased size to the last partition, and then rebuild a swap partition.

The following are four different resize scenarios.

  1. Use the GParted open source tool to resize the ext4 root partition for an instance that has both the ext4 and swap partitions.
    Note:
    • In this scenario, you need to re-plan the current partition by using Live CD.
    • To prevent data loss, exercise caution when you adjust a partition.

    Assume that VM instance uses an ext4 root partition of 35 GB and a swap partition of 5 GB. The total size is 40 GB. After you resize the root volume from 40 GB to 50 GB, you want to add the increased size to the ext4 root partition.

    Procedure:
    1. Add a GParted ISO. You can download the ISO from the GParted official website https://gparted.org/download.php. We recommend that you download the amd64 iso, indicating that 64-bit operating systems are supported.
    2. After you add the ISO, set CD ROM as the first boot order and Hard Disk as the second. Then, the VM instance boots from CD ROM next time.
    3. Use GParted Live CD to boot the system and launch the console of the VM instance. After the GParted boot finished, follow the instructions and long-press the Enter key until you enter the graphical interface.
    4. In the GParted interface, right-click the original swap partition to delete it, resize ext4 from 35 GB to 46 GB, and create a new swap partition for the unallocated 4 GB.
      Figure 3. Delete Original swap Partition


      Figure 4. Resize ext4 from 35 GB 46 GB




      Figure 5. Create a 4 GB swap Partition




    5. Power off the VM instance, detach the ISO, and start the VM instance again.
    6. Launch the VM console and run the df -h command. Then, you can see that the size of the root partition is increased to 46 GB.
      [root@10-58-21-213 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 46G 1.2G 42G 3% /
    7. Enable the swap partition and modify the /etc/fstab disk partition table.
      [root@10-58-21-213 ~]# fdisk -l|grep vda
Disk /dev/vda: 53.7 GB, 53687091200 bytes, 104857600 sectors
/dev/vda1 * 2048 96468991 48233472 83 Linux
/dev/vda2 96468992 104857599 4194304 82 Linux swap / Solaris

[root@10-58-21-213 ~]# mkswap /dev/vda2
mkswap: /dev/vda2: warning: wiping old swap signature.
Setting up swapspace version 1, size = 4194300 KiB
no label, UUID=ed99f72b-aafb-43ad-be8f-fcd09794beb0
#You can see that the UUID of the swap partition is ed99f72b-aafb-43ad-be8f-fcd09794beb0.

[root@10-58-21-213 ~]# swapon /dev/vda2
#Enable the swap partition.

[root@10-58-21-213 ~]# free -m
 total used free shared buff/cache available
Mem: 911 106 671 6 133 657
Swap: 4095 0 4095

[root@10-58-21-213 ~]# sed -i '/swap/d' /etc/fstab
echo "UUID=ed99f72b-aafb-43ad-be8f-fcd09794beb0 swap swap defaults 0 0"
#Write the swap settings into the disk partition table so that it can be started automatically upon the VM boots.
    8. After you power off and reboot the VM instance, the ext4 partition of the root volume is resized successfully, and the swap partition reserves 4 GB.
  2. Use the LVM partition tool to resize the LVM partition for an instance that has both the xfs and swap partitions.
    Note: This method applies to the dynamic resizing of LVM partitions without the need of using other tools.

    Assume that the VM instance uses an LVM partition and formats the LVM partition as a boot partition, an xfs root partition, and a swap partition. In this scenario, the size of the xfs root partition and swap partition is 94 GB and 6 GB, respectively. Therefore, the total size is 100 GB. After you resize the root volume from 100 GB to 120 GB, you want to add the increased size to the xfs root partition.

    Procedure:
    1. View the current partition and the LVM partition. Here, the size of the boot partition, LVM partition, and swap partition is 500 MB, 94 GB, and 6 GB, respectively. The boot partition and LVM partition use /dev/vda1 and /dev/vda2, respectively. The path of the LVM partition and swap partition is /dev/vg/root and /dev/vg/swap, respectively.
      [root@10-0-44-221 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-root 94G 6.5G 88G 7% /
/dev/vda1 477M 104M 344M 24% /boot
#The boot partition is 500 MB and uses /dev/vda1.
#The LVM partition is 94 GB and uses /dev/vda2. Path: /dev/vg/root.
#The swap partition is 6 GB. Path: /dev/vg/swap.

[root@10-0-44-221 ~]# fdisk -l |grep vda
Disk /dev/vda: 128.8 GB, 128849018880 bytes, 251658240 sectors
/dev/vda1 * 2048 1026047 512000 83 Linux
/dev/vda2 1026048 209715199 104344576 8e Linux LVM

[root@10-0-44-221 ~]# pvdisplay |egrep "Name|Size"
 PV Name /dev/vda2
 VG Name vg
 PV Size 99.51 GiB / not usable 3.00 MiB
 PE Size 4.00 MiB
#The physical volume uses /dev/vda2.

[root@10-0-44-221 ~]# vgdisplay |egrep "Name|Size"
 VG Name vg
 VG Size 99.51 GiB
 PE Size 4.00 MiB
 alloc PE / Size 25463 / 99.46 GiB
 Free PE / Size 11 / 44.00 MiB
#The volume group information. Name: vg. This volume group will be resized.

[root@10-0-44-221 ~]# lvdisplay |egrep "Name|Size"
 LV Name root
 VG Name vg
 LV Size 93.59 GiB
 LV Name swap
 VG Name vg
 LV Size 5.88 GiB
#The logical volume information.
    2. After the resizing, run the fdisk /dev/vda command to partition the increased size, create a new partition by using n, set the new partition to LVM format by using t, and make the setting take effect by using w. To make the setting take effect immediately, run the partprobe command.
      [root@10-0-44-221 ~]# 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): p
Disk /dev/vda: 128.8 GB, 128849018880 bytes, 251658240 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: 0x0008168e
 Device Boot Start End Blocks Id System
/dev/vda1 * 2048 1026047 512000 83 Linux
/dev/vda2 1026048 209715199 104344576 8e Linux LVM
Command (m for help): n
Partition type:
 p primary (2 primary, 0 extended, 2 free)
 e extended
Select (default p):
Using default response p
Partition number (3,4, default 3):
First sector (209715200-251658239, default 209715200):
Using default value 209715200
Last sector, +sectors or +size{K,M,G} (209715200-251658239, default 251658239):
Using default value 251658239
Partition 3 of type Linux and of size 20 GiB is set
Command (m for help): t
Partition number (1-3, default 3):
Hex code (type L to list all codes): 8e 
Changed type of partition 'Linux' to 'Linux LVM'
Command (m for help): p
Disk /dev/vda: 128.8 GB, 128849018880 bytes, 251658240 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: 0x0008168e
 Device Boot Start End Blocks Id System
/dev/vda1 * 2048 1026047 512000 83 Linux
/dev/vda2 1026048 209715199 104344576 8e Linux LVM
/dev/vda3 209715200 251658239 20971520 83 Linux LVM
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.

[root@10-0-44-221 ~]# partprobe
    3. Create a physical volume for the newly formatted partition.
      [root@10-0-44-221 ~]# pvcreate /dev/vda3
 Physical volume "/dev/vda3" successfully created
#Create a physical volume.
    4. Extend the volume group.
      [root@10-0-44-221 ~]# vgextend vg /dev/vda3
 Volume group "vg" successfully extended
#Name of the volume group: vg. The new partition will be added to the volume group vg.
    5. Disable the swap partition and delete the original swap logical volume.
      [root@10-0-44-221 ~]# swapoff -a
[root@10-0-44-221 ~]# lvremove /dev/vg/swap
Do you really want to remove active logical volume swap? [y/n]: yes
 Logical volume "swap" successfully removed
    6. Add 20 GB to the logical volume /dev/vg/root.
      [root@10-0-44-221 ~]# lvextend -L +20G /dev/vg/root
 Size of logical volume vg/root changed from 93.59 GiB (23959 extents) to 113.59 GiB (29079 extents).
 Logical volume root successfully resized.
#Add 20 GB to /dev/vg/root.

[root@10-0-44-221 ~]# lvdisplay
 --- Logical volume ---
 LV Path /dev/vg/root
 LV Name root
 VG Name vg
 LV UUID UkyCVW-gd5E-Z4Q2-bVHv-T84e-c3GH-ZMiUdF
 LV Write Access read/write
 LV Creation host, time localhost, 2017-07-26 13:18:40 +0800
 LV Status available
 # open 1
 LV Size 113.59 GiB
 Current LE 29079
 Segments 2
 allocation inherit
 Read ahead sectors auto
 - currently set to 8192
 Block device 253:0
    7. Run the xfs_growfs command to resize the XFS file system, make the new size take effect, and check the new partition.
      [root@10-0-44-221 ~]# xfs_growfs /dev/vg/root
meta-data=/dev/mapper/vg-root isize=256 agcount=4, agsize=6133504 blks
 = sectsz=512 attr=2, projid32bit=1
 = crc=0 finobt=0
data = bsize=4096 blocks=24534016, imaxpct=25
 = sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal bsize=4096 blocks=11979, version=2
 = sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 24534016 to 29776896

[root@10-0-44-221 ~]# df -h|grep vg-root
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-root 114G 6.5G 108G 6% /
#Resizing of the new partition takes effect.
    8. Divide a new size from the logical volume group to the swap partition, enable the swap partition, and write the disk configuration.
      [root@10-0-44-221 ~]# lvcreate -L 4G -n swap vg
 Logical volume "swap" created.
#Create a 4 GB partition named swap from the volume group vg.

[root@10-0-44-221 ~]# mkswap /dev/vg/swap
Setting up swapspace version 1, size = 4194300 KiB
no label, UUID=bfc8a843-c758-4665-adfe-e32752ceda44
#Create a swap partition. Here, you can see that the UUID of the swap partition is bfc8a843-c758-4665-adfe-e32752ceda44.

[root@10-0-44-221 ~]# swapon /dev/mapper/vg-swap
#Enable the swap partition.

[root@10-58-21-213 ~]# sed -i '/swap/d' /etc/fstab
echo "UUID=bfc8a843-c758-4665-adfe-e32752ceda44 swap swap defaults 0 0"
#Write the swap settings into the disk partition table so that the swap partition can be enabled automatically after the VM instance is started.
    9. After you power off and reboot the VM instance, the XFS system of the VM LVM partition is resized successfully, and the swap partition reserves 4 GB.
  3. Use the growpart tool to extend the xfs root partition instance.
    Note: This method applies to the dynamic resizing of xfs partitions without the need of attaching an ISO or using an LVM partition tool.

    Assume that the size of the xfs root partition is 6 GB and the total root volume size is 8 GB. After you resize the root volume from 8 GB to 40 GB, you want to add the increased size to the xfs root partition.

    Procedure:
    1. View the current partition. You can see that the root volume is resized to 40 GB, of which the xfs root partition is 6 GB. The extra disk space is unallocated and is not added to the disk partition.
      [root@10-0-44-210 ~]# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0  400G  0 disk
└─sda1   8:1    0  400G  0 part /mnt/nfs-data
vda    253:0    0   40G  0 disk
├─vda1 253:1    0    2G  0 part [SWAP]
└─vda2 253:2    0    6G  0 part /
    2. Install the growpart tool.
      [root@10-0-44-210 ~]# yum install -y cloud-utils-growpart
    3. Resize the xfs root partition by using the growpart <DeviceName> <PartionNumber> command. Here, the DeviceName of the xfs root partition is /dev/vda and PartionNumber is 2.
      [root@10-0-44-210 ~]# growpart /dev/vda 2
CHANGED: partition=2 start=4196352 old: size=12580864 end=16777216 new: size=79689695 end=83886047
    4. View the partitions. Then, you can see that the xfs root partition is resized from 6 GB to 38 GB.
      [root@10-0-44-210 ~]# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0  400G  0 disk
└─sda1   8:1    0  400G  0 part /mnt/nfs-data
vda    253:0    0   40G  0 disk
├─vda1 253:1    0    2G  0 part [SWAP]
└─vda2 253:2    0   38G  0 part /
    5. Extend the XFS file system.
      1. To extend the XFS file system, make sure that the xfsprogs tool is installed. The installation command is as follows:
        [root@10-0-44-210 ~]# yum install xfsprogs
      2. Extend the file system in /dev/vda2 by running the xfs_growfs command. Here, / is the mount point.
        [root@10-0-44-210 ~]# xfs_growfs /
meta-data=/dev/vda2              isize=256    agcount=26, agsize=393152 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=0        finobt=0 spinodes=0
data     =                       bsize=4096   blocks=9961211, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal               bsize=4096   blocks=2560, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
data blocks changed from 1572608 to 9961211
      3. Check whether the file system reflects the increased volume size.
        [root@10-0-44-210 ~]# df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/vda2        38G  3.3G   35G   9% /
    Note: We recommend that you install the expansion and formatting tools according to the actual operating system. For example,
    • For CentOS 7, install the following tool:
      yum install cloud-utils-growpart
yum install xfsprogs
    • For Ubuntu 14, Ubuntu 16, Ubuntu 18, and Debian 9, install the following tool:
      apt install cloud-guest-utils
apt install xfsprogs
    • For Debian 8, openSUSE 42.3, openSUSE 13.1, and SLES 12 SP2, use the growpart or xfsprogs tool of the upstream version.
  4. Resize the Windows partitions.
    You can resize disks of Windows partitions on the disk management page.
    Note: After you resize the disk of a Windows partition, scan the disk to take effect.