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How to Resize LVM Partition Inside an Extended Partition

Resizing a logical volume in Linux is not very difficult but it can be tricky if the root is under an extended partition.

Rakesh Jain
Rakesh Jain

Table of Contents

Resizing a logical volume in Linux is not very difficult and can be achieved through very straightforward approach. Here are the usual steps:

  1. Create a new partition on hard disk.
  2. Add the partition you just created as a physical volume.
  3. Add the new physical volume to the volume group.
  4. Assign space from the volume group to the logical volume.
  5. Resize the filesystem.

But in this scenario, you have the root filesystem (as an LVM partition) mounted under an extended partition, not within a primary partition. You just have one primary partition which is mounted on /boot and rest all space is part of that extended partition.

Sounds troublesome? Let me show you how to resize LVM inside extended partition.

Resizing LVM partition inside extended partition

I am using a Linux installed in virtual machine in this tutorial.

Please keep in mind that you should be very careful while dealing with disk partitions.

Step 1:  Shut down your VM and increase the disk size

First, shut down your VM and increase the disk size. Here, I have increased the disk /dev/sda size by 20 GB to around 40 GB. Then start your VM and go to the console.

Have a look at our disk partitions.

[email protected]:~# fdisk -l

Disk /dev/sda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders, total 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 identifier: 0x000a975f

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      499711      248832   83  Linux
/dev/sda2          501758    41940991    20719617    5  Extended
/dev/sda5          501760    41940991    20719616   8e  Linux LVM

If you analyze the disk space with df command, here's what it shows for me:

[email protected]:~# df -hT
Filesystem     Type      Size  Used Avail Use% Mounted on
udev           devtmpfs  989M  4.0K  989M   1% /dev
tmpfs          tmpfs     201M  716K  200M   1% /run
/dev/dm-0      ext4       19G  1.5G   16G   9% /
none           tmpfs     4.0K     0  4.0K   0% /sys/fs/cgroup
none           tmpfs     5.0M     0  5.0M   0% /run/lock
none           tmpfs    1001M     0 1001M   0% /run/shm
none           tmpfs     100M     0  100M   0% /run/user
/dev/sda1      ext2      236M   40M  184M  18% /boot

Here, the object is to increase the size of the partition /dev/dm-0 which is mounted on /dev/sda5.

Let me also show the current status of physical volumes, volume groups and logical volumes:

[email protected]:~# lvs
  LV     VG          Attr      LSize    Pool Origin Data%  Move Log Copy%  Convert
  root   ubuntu14-vg -wi-ao---   18.74g                                           
  swap_1 ubuntu14-vg -wi-ao--- 1020.00m   
  
[email protected]:~# pvs
  PV         VG          Fmt  Attr PSize  PFree 
  /dev/sda5  ubuntu14-vg lvm2 a--  19.76g 20.00m
  
[email protected]:~# vgs
  VG          #PV #LV #SN Attr   VSize  VFree 
  ubuntu14-vg   1   2   0 wz--n- 19.76g 20.00m

They all have around 20 GB of storage space assigned to them.

Step 2: Begin the LVM resizing process

Here are the steps for resizing the LVM partition:

Open fdisk utility and look at the partitions:

[email protected]:~# fdisk /dev/sda

Command (m for help): p

Disk /dev/sda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders, total 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 identifier: 0x000a975f

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      499711      248832   83  Linux
/dev/sda2          501758    41940991    20719617    5  Extended
/dev/sda5          501760    41940991    20719616   8e  Linux LVM

Delete the extended partition (/dev/sda2) using command d, which will automatically delete the underlying LVM partition which is /dev/sda5.

Command (m for help): d
Partition number (1-5): 2

Create a new partition again as extended using command n with default start and end cylinder values.

Command (m for help): n
Partition type:
   p   primary (1 primary, 0 extended, 3 free)
   e   extended
Select (default p): e
Partition number (1-4, default 2): 
Using default value 2
First sector (499712-83886079, default 499712): 
Using default value 499712
Last sector, +sectors or +size{K,M,G} (499712-83886079, default 83886079): 
Using default value 83886079

Command (m for help): p

Disk /dev/sda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders, total 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 identifier: 0x000a975f

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      499711      248832   83  Linux
/dev/sda2          499712    83886079    41693184    5  Extended

Create a logical partition (dev/sda5) using the default start and end cylinder values.

Command (m for help): n
Partition type:
   p   primary (1 primary, 1 extended, 2 free)
   l   logical (numbered from 5)
Select (default p): l
Adding logical partition 5
First sector (501760-83886079, default 501760): 
Using default value 501760
Last sector, +sectors or +size{K,M,G} (501760-83886079, default 83886079): 
Using default value 83886079

Switch to expert mode by pressing x.

Command (m for help): x

Run expert command b to adjust the beginning of the partition (this changes the partition size, not where it ends). Enter the start value as it was earlier before deleting the partitions. Here it is 501760.

Expert command (m for help): b
Partition number (1-5): 5
New beginning of data (499713-83886079, default 501760): 501760

Then run r to return to the main menu.

Expert command (m for help): r

Check the partition number just to make sure.

Command (m for help): p

Disk /dev/sda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders, total 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 identifier: 0x000a975f

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      499711      248832   83  Linux
/dev/sda2          499712    83886079    41693184    5  Extended
/dev/sda5          501760    83886079    41692160   83  Linux

Now change the partition type to LVM by pressing t command and chose type 8e.

Command (m for help): t
Partition number (1-5): 5
Hex code (type L to list codes): 8e
Changed system type of partition 5 to 8e (Linux LVM)

Press w to write all the changes to the disk.

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.

Step 3: Make manual changes to physical and logical volume

Run partprobe command to inform OS about partition table changes:

[email protected]:~# partprobe /dev/sda

Run lsblk command to see that /dev/sda5 is now around 40 GB in size (for me).

[email protected]:~# lsblk 
NAME                           MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda                              8:0    0    40G  0 disk 
├─sda1                           8:1    0   243M  0 part /boot
├─sda2                           8:2    0     1K  0 part 
└─sda5                           8:5    0  39.8G  0 part 
  ├─ubuntu14--vg-root (dm-0)   252:0    0  18.8G  0 lvm  /
  └─ubuntu14--vg-swap_1 (dm-1) 252:1    0  1020M  0 lvm  [SWAP]
sr0                             11:0    1  1024M  0 rom  

Run the df command and you'll notice that /dev/dm-0  still shows the old size details:

[email protected]:~# df -hT
Filesystem     Type      Size  Used Avail Use% Mounted on
udev           devtmpfs  989M  4.0K  989M   1% /dev
tmpfs          tmpfs     201M  716K  200M   1% /run
/dev/dm-0      ext4       19G  1.5G   16G   9% /
none           tmpfs     4.0K     0  4.0K   0% /sys/fs/cgroup
none           tmpfs     5.0M     0  5.0M   0% /run/lock
none           tmpfs    1001M     0 1001M   0% /run/shm
none           tmpfs     100M     0  100M   0% /run/user
/dev/sda1      ext2      236M   40M  184M  18% /boot

Same is the case with Physical volumes, Volume groups and Logical volumes:

[email protected]:~# lvs
  LV     VG          Attr      LSize    Pool Origin Data%  Move Log Copy%  Convert
  root   ubuntu14-vg -wi-ao---   18.74g                                           
  swap_1 ubuntu14-vg -wi-ao--- 1020.00m   
  
[email protected]:~# pvs
  PV         VG          Fmt  Attr PSize  PFree 
  /dev/sda5  ubuntu14-vg lvm2 a--  19.76g 20.00m
  
[email protected]:~# vgs
  VG          #PV #LV #SN Attr   VSize  VFree 
  ubuntu14-vg   1   2   0 wz--n- 19.76g 20.00m

You'l have to do some manual effort here.

Resize the Physical volume:

[email protected]:~# pvresize /dev/sda5 
Physical volume "/dev/sda5" changed
1 physical volume(s) resized / 0 physical volume(s) not resized

Now check Physical Volume and Volume group status and see that it is properly showing the new size:

[email protected]:~# pvs
PV         VG          Fmt  Attr PSize  PFree 
/dev/sda5  ubuntu14-vg lvm2 a--  39.76g 20.02g

[email protected]:~# vgs
VG          #PV #LV #SN Attr   VSize  VFree 
ubuntu14-vg   1   2   0 wz--n- 39.76g 20.02g

Similarly, resize the logical volume:

[email protected]:~# lvextend -l +100%FREE /dev/ubuntu14-vg/root
  Extending logical volume root to 38.76 GiB
  Logical volume root successfully resized

Lastly, resize the filesystem:

[email protected]:~# resize2fs /dev/ubuntu14-vg/root
resize2fs 1.42.9 (4-Feb-2014)
Filesystem at /dev/ubuntu14-vg/root is mounted on /; on-line resizing required
old_desc_blocks = 2, new_desc_blocks = 3
The filesystem on /dev/ubuntu14-vg/root is now 10161152 blocks long.

Verify the disk status and see that LVM is now resized properly:

[email protected]:~# df -hT
Filesystem     Type      Size  Used Avail Use% Mounted on
udev           devtmpfs  989M  4.0K  989M   1% /dev
tmpfs          tmpfs     201M  716K  200M   1% /run
/dev/dm-0      ext4       39G  1.5G   35G   4% /
none           tmpfs     4.0K     0  4.0K   0% /sys/fs/cgroup
none           tmpfs     5.0M     0  5.0M   0% /run/lock
none           tmpfs    1001M     0 1001M   0% /run/shm
none           tmpfs     100M     0  100M   0% /run/user
/dev/sda1      ext2      236M   40M  184M  18% /boot

That's all! You have successfully resized the LVM partition inside an extended partition.

Complete Beginner’s Guide to LVM in Linux [With Hands-on]
Everything necessary you need to know and learn about the logical volume management in Linux.

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