mjhjmtu

I have a CentOS7.2 server, and when I install the system, I did not take notice of the disk, now I have a big /dev/centos/home:

[root@controller dev]# lvdisplay
 --- Logical volume ---
 LV Path /dev/centos/swap
 LV Name swap
 VG Name centos
 LV UUID WofWvD-KQEG-hyaf-TSvf-bLxW-d6Gh-onWriz
 LV Write Access read/write
 LV Creation host, time localhost.localdomain, 2017-08-30 12:40:47 +0800
 LV Status available
 # open 2
 LV Size 7.88 GiB
 Current LE 2016
 Segments 1
 Allocation inherit
 Read ahead sectors auto
 - currently set to 256
 Block device 253:1

 --- Logical volume ---
 LV Path /dev/centos/home
 LV Name home
 VG Name centos
 LV UUID gZlLHM-bWuj-8lXu-8ete-VpZI-zz1w-3AC5rP
 LV Write Access read/write
 LV Creation host, time localhost.localdomain, 2017-08-30 12:40:47 +0800
 LV Status available
 # open 1
 LV Size 873.08 GiB
 Current LE 223509
 Segments 1
 Allocation inherit
 Read ahead sectors auto
 - currently set to 256
 Block device 253:2

 --- Logical volume ---
 LV Path /dev/centos/root
 LV Name root
 VG Name centos
 LV UUID PKqlOW-SIa8-df24-AVbl-BZMG-n0dn-89kjB3
 LV Write Access read/write
 LV Creation host, time localhost.localdomain, 2017-08-30 12:40:51 +0800
 LV Status available
 # open 1
 LV Size 50.00 GiB
 Current LE 12800
 Segments 1
 Allocation inherit
 Read ahead sectors auto
 - currently set to 256
 Block device 253:0

Now, I want to divide the /dev/centos/home, isolate part of it to be a VG, so I can use it as other usage. Such as use it to pvcreate.

I don't know whether I can divide the /dev/centos/home, because I scare loss data, or break the operate system. But I really need a VG from there to pvcreate, or if there is a other method to do that.

Close all programs that use this volume. In the system must be only the root user (safest way might be to comment out /home in /etc/fstab, then have a reboot, log as root as Archemar has mentioned below. See more in comments)

First you need to unmount partition:

umount /dev/centos/home

Then check filesystem (if you skip this step the there may be data loss):

e2fsck -fy /dev/centos/home

Resize partition:

resize2fs /dev/centos/home 50G

where 50g is desired size after shrinking. This size must be greather then used space on partition (see output of df -h and set up size a bit more of used space ).

Reduce logical partition:

lvreduce -L 51G /dev/centos/home

pay attention: partition size with lvreduce more than with resize2fs.

Run resize2fs again (to use remaining of ~1G space):

resize2fs /dev/centos/home

Mount volume:

mount -a

You need to backup all data before this changes!