Extend Partition CentOS 7 – How to Extend Partition with Unallocated Space on CentOS 7

centos7disk-space-utilization

I have centos 7 server (CentOS Linux release 7.3.1611 (Core)) When I was updated my server I saw error you need extra space. But I had 20GB disk on server when I check disk spaces I saw only 4.5GB partition created and 16GB partition is free space no unallocated.
How I can extend partition from 16GB free space?

lsblk:

NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
fd0               2:0    1    4K  0 disk
sda               8:0    0   20G  0 disk
├─sda1            8:1    0  500M  0 part /boot
└─sda2            8:2    0  4.5G  0 part
  ├─centos-root 253:0    0    4G  0 lvm  /
  └─centos-swap 253:1    0  512M  0 lvm  [SWAP]
sr0              11:0    1 1024M  0 rom

Best Answer

There are three steps to make:

alter your partition table so sda2 ends at end of disk
reread the partition table (will require a reboot)
resize your LVM pv using pvresize

Step 1 - Partition table

Run fdisk /dev/sda. Issue p to print your current partition table and copy that output to some safe place. Now issue d followed by 2 to remove the second partition. Issue n to create a new second partition. Make sure the start equals the start of the partition table you printed earlier. Make sure the end is at the end of the disk (usually the default).

Issue t followed by 2 followed by 8e to toggle the partition type of your new second partition to 8e (Linux LVM).

Issue p to review your new partition layout and make sure the start of the new second partition is exactly where the old second partition was.

If everything looks right, issue w to write the partition table to disk. You will get an error message from partprobe that the partition table couldn't be reread (because the disk is in use).

Reboot your system

This step is neccessary so the partition table gets re-read.

Resize the LVM PV

After your system rebooted invoke pvresize /dev/sda2. Your Physical LVM volume will now span the rest of the drive and you can create or extend logical volumes into that space.

1. Create Partitions on sdb

Just as you did create the partitions on sdb. Make sure sdb1 has the same start and end values as sda1. Create sdb2 just as you did earlier (i.e. not the whole rest of the drive)

2. Clone sda1 to sdb1

Remount /dev/sda1 in read-only mode with mount -o remount,ro /boot and clone the partition dd if=/dev/sda1 of=/dev/sdb1.

3. Swap drives and make sure sdb boots

Swap sda and sdb. Install the bootloader on the new sda and make sure the bootloader still loads the kernel when the new sdb (i.e. the original drive) is not connected. Boot will panic because there's no root volume, but you now know that it can boot. Reattach sdb.

3. Extend your Volume Group

Add the new sda2 to your volume group like this: pvcreate /dev/sda2 and vgextend centos /dev/sda2

4. Move over your swap and root volumes

The following commands will move not clone your volumes onto your new drive. The will however stay in the same volume group

pvmove -n swap /dev/sdb2 /dev/sda2
pvmove -n root /dev/sdb2 /dev/sda2

5. Clone your /home

Create a new volume for /home on sda2, mount it somewhere and clone the contents with xfsdump and xfsrestore

lvcreate --size 77,50G --name new_home centos /dev/sda2
mount /dev/centos/new_home /mnt
xfsdump -J /home | xfsrestore -J /mnt

6. Make sure selinux labels got transferred

Check that ls -Z /home and ls -Z /mnt match

7. Rename home volumes

Umount both home volumes and rename them accordingly

umount /home
umount /mnt
lvrename centos/home centos/old_home
lvrename centos/new_home centos/home
mount /home

You have now your cloned smaller /home mounted. The volume centos/old_home is the last one still on sdb2. At this point your system should boot and run without any hassle, but you still need to get rid of sdb.

8. Cleanup

After your have rebooted and made sure everything still works as expected you can remove the old home volume using lvremove centos/old_home. When you look at the output of pvs you should notice that sdb2 should be completely unused.

At this point you can vgreduce centos /dev/sdb2 and pvremove /dev/sdb2 so the "old" drive is no more part of your volume group.

You can now shutdown the box and remove the old drive.