How to expand the disk partition for centos system

root@eve-ng:~# df -h
Filesystem Size Used Avail Use% Mounted on
udev 7.9G 0 7.9G 0% /dev
tmpfs 1.6G 19M 1.6G 2% /run
/dev/mapper/eve--ng--vg-root 38G 13G 23G 36% /
tmpfs 7.9G 0 7.9G 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 7.9G 0 7.9G 0% /sys/fs/cgroup
/dev/sda1 472M 83M 365M 19% /boot

root@eve-ng:~# fdisk -l
...omit some content Disk /dev/sda: 250 GiB, 268435456000 bytes, 524288000 sectors //You can see that there are already 250G Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x3e3ca055

Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 999423 997376 487M 83 Linux
/dev/sda2 1001470 83884031 82882562 39.5G 5 Extended
/dev/sda5 1001472 83884031 82882560 39.5G 8e Linux LVM

Disk /dev/mapper/eve--ng--vg-root: 38.6 GiB, 41406169088 bytes, 80871424 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 /dev/mapper/eve--ng--vg-swap_1: 980 MiB, 1027604480 bytes, 2007040 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

//Execute the partition below root@eve-ng:~# fdisk /dev/sda

Welcome to fdisk (util-linux 2.27.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help): n
Partition type
  p primary (1 primary, 1 extended, 2 free)
  l logical (numbered from 5)
Select (default p): p
Partition number (3,4, default 3): 3
First sector (999424-524287999, default 999424): 83884032 //Note that this is the last block allocated before (sda5 end) plus one (83884031+1)
Last sector, +sectors or +size{K,M,G,T,P} (83884032-524287999, default 524287999): //Note whether this is the last block. Created a new partition 3 of type 'Linux' and of size 210 GiB.

Command (m for help): t
Partition number (1-3,5, default 5): 3 3
Partition type (type L to list all types): 8e

Changed type of partition 'Linux' to 'Linux LVM'.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Re-reading the partition table failed.: 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).

root@eve-ng:~# reboot

root@eve-ng:~# pvcreate /dev/sda3
 Physical volume "/dev/sda3" successfully created
root@eve-ng:~# vgdisplay
 --- Volume group ---
 VG Name eve-ng-vg
 System ID
 Format lvm2
 Metadata Areas 1
 Metadata Sequence No 3
 VG Access read/write
 VG Status resizable
 MAX LV 0
 Cur LV 2
 Open LV 2
 Max PV 0
 Cur PV 1
 Act PV 1
 VG Size 39.52 GiB
 PE Size 4.00 MiB
 Total PE 10117
 Alloc PE / Size 10117 / 39.52 GiB
 Free PE / Size 0 / 0
 VG UUID EvwUbc-nfsg-dHqA-znxB-U3gv-V782-Q8ZxkI

root@eve-ng:~# vgextend eve-ng-vg /dev/sda3
 Volume group "eve-ng-vg" successfully extended
root@eve-ng:~# vgdisplay
 --- Volume group ---
 VG Name eve-ng-vg
 System ID
 Format lvm2
 Metadata Areas 2
 Metadata Sequence No 4
 VG Access read/write
 VG Status resizable
 MAX LV 0
 Cur LV 2
 Open LV 2
 Max PV 0
 Cur PV 2
 Act PV 2
 VG Size 249.52 GiB
 PE Size 4.00 MiB
 Total PE 63877
 Alloc PE / Size 10117 / 39.52 GiB
 Free PE / Size 53760 / 210.00 GiB
 VG UUID EvwUbc-nfsg-dHqA-znxB-U3gv-V782-Q8ZxkI

root@eve-ng:~# lvdisplay
 --- Logical volume ---
 LV Path /dev/eve-ng-vg/root
 LV Name root
 VG Name eve-ng-vg
 LV UUID ktUpR0-VpqS-rJJv-a1FC-u6Gd-U8yN-2WYQ53
 LV Write Access read/write
 LV Creation host, time eve-ng, 2018-03-21 02:25:21 +0200
 LV Status available
 # open 1
 LV Size 38.56 GiB
 Current LE 9872
 Segments 1
 Allocation inherit
 Read ahead sectors auto
 - currently set to 256
 Block device 253:0

//Extend logical volume root@eve-ng:~# lvextend -l +100%FREE /dev/eve-ng-vg/root
 Size of logical volume eve-ng-vg/root changed from 38.56 GiB (9872 extents) to 248.56 GiB (63632 extents).
 Logical volume root successfully resized.

root@eve-ng:~# df -h
Filesystem Size Used Avail Use% Mounted on
udev 7.9G 0 7.9G 0% /dev
tmpfs 1.6G 19M 1.6G 2% /run
/dev/mapper/eve--ng--vg-root 38G 13G 23G 36% /
tmpfs 7.9G 0 7.9G 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 7.9G 0 7.9G 0% /sys/fs/cgroup
/dev/sda1 472M 83M 365M 19% /boot

//For online capacity expansion, you must first check the type of the current file system. You can view it through cat /etc/fstab root@eve-ng:~# resize2fs /dev/eve-ng-vg/root
resize2fs 1.42.13 (17-May-2015)
Filesystem at /dev/eve-ng-vg/root is mounted on /; on-line resizing required
old_desc_blocks = 3, new_desc_blocks = 16
The filesystem on /dev/eve-ng-vg/root is now 65159168 (4k) blocks long.

root@eve-ng:~# df -h
Filesystem Size Used Avail Use% Mounted on
udev 7.9G 0 7.9G 0% /dev
tmpfs 1.6G 19M 1.6G 2% /run
/dev/mapper/eve--ng--vg-root 245G 13G 222G 6% /
tmpfs 7.9G 0 7.9G 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 7.9G 0 7.9G 0% /sys/fs/cgroup
/dev/sda1 472M 83M 365M 19% /boot