How to extend root filesystem using LVM on Linux

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Welcome to our guide on how to extend root filesystem using LVM on Linux. This will cover both ext4 and XFS filesystem root partition extending. To demonstrate a complete LVM lifecycle, we will perform the following actions:

  • Create an LVM physical volume, volume group, and logical volume.
  • Create an XFS and ext4 file systems on the logical volumes
  • Extend LVM logical volumes ( root and non-root filesystem)

LVM allows you to create, resize or delete partitions on a running system without requiring any reboot. So check the steps below to extend root filesystem using LVM in Linux. You can skip some steps which don’t apply to use.

If you’re not using LVM, check our guide below which covers extending Ext2/3/4 and XFS file systems.

Step 1: Confirm Disk Partitions in Distribution.

Before we can do any extension, let’s just confirm our disk layout / partitioning scheme.

$ lsblk 
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0            11:0    1 1024M  0 rom  
vda           252:0    0   30G  0 disk 
├─vda1        252:1    0    1G  0 part /boot
└─vda2        252:2    0   29G  0 part 
  ├─rhel-root 253:0    0 26.9G  0 lvm  /
  └─rhel-swap 253:1    0  2.1G  0 lvm  [SWAP]

As noted, we have a root filesystem on /dev/vda2 physical volume.

$ sudo pvs
  PV         VG   Fmt  Attr PSize   PFree
  /dev/vda2  rhel lvm2 a--  <29.00g    0 

Step 2: Extend your OS root disk

As shown in step 1, my root filesystem is on a 30GB disk. I’ll grow it to 40GB by extending the virtual disk (VM disk device).

I use KVM virtualization technology, so this guide works for me: How to extend/increase KVM Virtual Machine (VM) disk size

$ lsblk 
 NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
 sr0            11:0    1 1024M  0 rom  
 vda           252:0    0   40G  0 disk 
 ├─vda1        252:1    0    1G  0 part /boot
 └─vda2        252:2    0   29G  0 part 
   ├─rhel-root 253:0    0 26.9G  0 lvm  /
   └─rhel-swap 253:1    0  2.1G  0 lvm  [SWAP]

If you’re on a different Virtualization platform, refer to its documentation for how to extend OS disk.

Once the OS block device is resized, ssh to your Linux machine and extend LVM to use newly added disk capacity. The command below will expand the last partition (Partition 2), as shown by 252:2,on the disk (/dev/vda) to the maximum size the disk provides.

Install cloud utils package on the system

For those new to growpart, it is a Linux command line tool used to extend a partition in a partition table to fill available space. This command is provided by cloud utils package.

On Ubuntu / Debian system, run the commands below to install growpart tool.

sudo apt install cloud-guest-utils

For CentOS server, run

sudo yum -y install cloud-utils-growpart

Help page can be viewed by passing -h argument

$ growpart -h
growpart disk partition
   rewrite partition table so that partition takes up all the space it can
   options:
    -h | --help       print Usage and exit
         --fudge F    if part could be resized, but change would be
                      less than 'F' bytes, do not resize (default: 1048576)
    -N | --dry-run    only report what would be done, show new 'sfdisk -d'
    -v | --verbose    increase verbosity / debug
    -u | --update  R update the the kernel partition table info after growing
                      this requires kernel support and 'partx --update'
                      R is one of:
                       - 'auto'  : [default] update partition if possible
                       - 'force' : try despite sanity checks (fail on failure)
                       - 'off'   : do not attempt
                       - 'on'    : fail if sanity checks indicate no support

   Example:
    - growpart /dev/sda 1
      Resize partition 1 on /dev/sd

Now use growpart to extend your partition. In this example we’re extending partition in disk /dev/vda. Replace 2 and /dev/vda with your correct values.

$ sudo growpart /dev/vda 2
CHANGED: partition=2 start=2099200 old: size=18872320 end=20971520 new: size=60815327,end=62914527

Confirm if the change was successful.

$ lsblk 
 NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
 sr0            11:0    1 1024M  0 rom  
 vda           252:0    0   40G  0 disk 
 ├─vda1        252:1    0    1G  0 part /boot
 └─vda2        252:2    0   39G  0 part 
   ├─rhel-root 253:0    0 26.9G  0 lvm  /
   └─rhel-swap 253:1    0  2.1G  0 lvm  [SWAP]

Step 3: Resize root logical volume to occupy all space

Resize physical volume.

$ sudo pvresize /dev/vda2
  Physical volume "/dev/vda2" changed
  1 physical volume(s) resized or updated / 0 physical volume(s) not resized

$ sudo pvs
  PV         VG   Fmt  Attr PSize   PFree 
  /dev/vda2  rhel lvm2 a--  <39.00g 10.00g

Check the size of the volume group configured.

$ sudo vgs
   VG   #PV #LV #SN Attr   VSize   VFree 
   rhel   1   2   0 wz--n- <39.00g 10.00g

Then resize logical volume used by the root file system using the extended volume group:

sudo lvextend -r -l +100%FREE /dev/name-of-volume-group/root

This extends the logical volume to use all available capacity in the volume group. With the + sign the value is added to the actual size of the logical volume.

Command options used:

  • -l – extend or set the logical volume size in units of logical extents
  • -r – Resize underlying filesystem together with the logical volume

Here’s an example of my setup file system extension:

$ df -hT | grep mapper
 /dev/mapper/rhel-root xfs        27G  1.9G   26G   8% /

$ sudo lvextend -r -l +100%FREE /dev/mapper/rhel-root
Size of logical volume rhel/root changed from <26.93 GiB (6893 extents) to <36.93 GiB (9453 extents).
Logical volume rhel/root successfully resized.

If you prefer setting the size to be extended manually, use command option:

-L, --size [+]LogicalVolumeSize[bBsSkKmMgGtTpPeE]

Where size suffix are:

  • M for megabytes
  • G for gigabytes
  • T for terabytes
  • P for petabytes
  • E for exabytes

Without the sign the value is taken as an absolute one.

# Add 20 gigabytes to the current logical volume size
$ sudo lvextend -r -L +20G /dev/name-of-volume-group/root

Step 4: Update changes on the filesystem (If you didn’t use -r option in step 3)

Your root filesystem will still show the old size.

$ df -hT | grep mapper
 /dev/mapper/rhel-root xfs        27G  1.9G   26G   8% /

Let’s make the filesystem report the actual size, including extended.

For ext4 filesystem

sudo resize2fs /dev/name-of-volume-group/root

For xfs filesystem

$ sudo xfs_growfs /
 meta-data=/dev/mapper/rhel-root  isize=512    agcount=4, agsize=1764608 blks
          =                       sectsz=512   attr=2, projid32bit=1
          =                       crc=1        finobt=1, sparse=1, rmapbt=0
          =                       reflink=1
 data     =                       bsize=4096   blocks=7058432, imaxpct=25
          =                       sunit=0      swidth=0 blks
 naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
 log      =internal log           bsize=4096   blocks=3446, version=2
          =                       sectsz=512   sunit=0 blks, lazy-count=1
 realtime =none                   extsz=4096   blocks=0, rtextents=0
 data blocks changed from 7058432 to 9679872

Conclusion

You have learned how to extend root filesystem backed by nfs and ext4 with this how to extend root filesystem using LVM guide. I hope this was helpful and would like to thank you for reading.

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A systems engineer with excellent skills in systems administration, cloud computing, systems deployment, virtualization, containers, and a certified ethical hacker.