filesystem

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Last Updated: 11/6/2024

WARNING: This content is still being edited. Please review carefully before use.

We are going to use this page to review part of the a file system. In this example we are going to work with an Ubuntu

root@resize:/etc# lsblk
NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda                         8:0    0   16G  0 disk
├─sda1                      8:1    0    1M  0 part
├─sda2                      8:2    0  1.8G  0 part /boot
└─sda3                      8:3    0 14.2G  0 part
  └─ubuntu--vg-ubuntu--lv 252:0    0   10G  0 lvm  /
sr0                        11:0    1 1024M  0 rom

One question might be…. how can I tell if my disk system is using either the GPT or MBR partitioning scheme.

root@resize:/etc# parted -l
Model: VMware Virtual disk (scsi)
Disk /dev/sda: 17.2GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  2097kB  1049kB                     bios_grub
 2      2097kB  1881MB  1879MB  ext4
 3      1881MB  17.2GB  15.3GB


Model: Linux device-mapper (linear) (dm)
Disk /dev/mapper/ubuntu--vg-ubuntu--lv: 10.7GB
Sector size (logical/physical): 512B/512B
Partition Table: loop
Disk Flags:

Number  Start  End     Size    File system  Flags
 1      0.00B  10.7GB  10.7GB  ext4

So in this case we have a SCSI presented disk. We are using VMWare for virtualization. The disk is configured as 16GB. It describes the partition table as GPT: And then we see 3 partitions.

And just to examine the 3rd partition we can use the following which will confirm that this partition is made over for LVM. (in short; instead of being directly used as ext2, ext3, ext4, xfs, etc…. the partition is LVM2 PV which means it is reserved for use by the Logical Volume Manager)

root@resize:/home/ubuntu# file -sL /dev/sda3
/dev/sda3: LVM2 PV (Linux Logical Volume Manager), UUID: 6ZQt8m-r4AN-CI39-FK59-5nMs-83GH-NPljaH, size: 15297675264

CHANGE THE DISK SIZE

Let’s say we resize the disk from 16 to 20 GB in VMWare.

The following 2 lines might be needed in order to encourage the OS to recognize the change

rescan-scsi-bus.sh --nosync -f -a -r -m

And

rescan-scsi-bus.sh -a

If I am being honest the above can be a little hit or miss. Some times a rescan works.

echo 1 > /sys/block/sda/device/rescan

Now the above can be done without restarting the VM. If all else fails, I would restart the VM and see what that does for you.

Now when we check we should now see 20GB of space. (sda device)

root@resize:/etc# lsblk
NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda                         8:0    0   20G  0 disk
├─sda1                      8:1    0    1M  0 part
├─sda2                      8:2    0  1.8G  0 part /boot
└─sda3                      8:3    0 14.2G  0 part
  └─ubuntu--vg-ubuntu--lv 252:0    0   10G  0 lvm  /
sr0                        11:0    1 1024M  0 rom

EXTENDING THE VOLUME

We can use the growpart command.

STEP 1:

root@resize:/home/ubuntu# growpart /dev/sda 3
CHANGED: partition=3 start=3674112 old: size=29878272 end=33552383 new: size=38268895 end=41943006 root@resize:/home/ubuntu#

In short LVM2_VM partition now has additional space. When we look we now see that “sda3” has 18.2G (not the 14.2G we had before)

root@resize:/home/ubuntu# lsblk
NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda                         8:0    0   20G  0 disk
├─sda1                      8:1    0    1M  0 part
├─sda2                      8:2    0  1.8G  0 part /boot
└─sda3                      8:3    0 18.2G  0 part
  └─ubuntu--vg-ubuntu--lv 252:0    0 14.2G  0 lvm  /
sr0                        11:0    1 1024M  0 rom

Given that we can ask a question with PVS it will now confirm that their is 4.00G under PFree

root@resize:/home/ubuntu# pvs
  PV         VG        Fmt  Attr PSize   PFree
  /dev/sda3  ubuntu-vg lvm2 a--  <18.25g 4.00g

The question then becomes how can I add the 4 extra Gigs of space to the volume that has the Volume Group:ubuntu-vg and the Logical volume: ubuntu-lv

STEP 2

Now that we have made room we will grow the logical partition.

root@resize:/home/ubuntu# lvextend -l +100%FREE /dev/ubuntu-vg/ubuntu-lv
  Size of logical volume ubuntu-vg/ubuntu-lv changed from <14.25 GiB (3647 extents) to <18.25 GiB (4671 extents).
  Logical volume ubuntu-vg/ubuntu-lv successfully resized.

And now, by design, we have a 18.2G partition for root.

root@resize:/home/ubuntu# lsblk
NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda                         8:0    0   20G  0 disk
├─sda1                      8:1    0    1M  0 part
├─sda2                      8:2    0  1.8G  0 part /boot
└─sda3                      8:3    0 18.2G  0 part
  └─ubuntu--vg-ubuntu--lv 252:0    0 18.2G  0 lvm  /
sr0                        11:0    1 1024M  0 rom

References:
https://serverfault.com/questions/509468/how-to-extend-an-ext4-partition-and-filesystem

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