I don't use the /home logical volume that the Centos 6 Minimal Install script creates, so I delete it and either assign all the disk space to root, or create a different logical volume.
Get the names of the logical volumes with a df command:
[root@HOSTNAME ~]# df -H
Filesystem Size Used Available Use% Mounted on
/dev/mapper/vg_hostname-lv_root
150G 30G 120G 20% /
tmpfs 4G .10G 3.90G 1% /dev/shm
/dev/sda3 .5G .1G .4G 20% /boot
/dev/mapper/vg_hostname-lv_home
50G 10G 40G 20% /home
save any home directories created during the install...
mkdir /tmphome
cd /home
mv * /tmphome
cd /
unmount the logical volume to be deleted
umount /home
put the home directories back in /home...
mv /tmphome/* /home
remove the temporary directory...
rmdir /tmphome
Note: if the previous steps seemed illogical... there is a /home directory on the root filesystem. Previously, a logical volume/filesystem, effectively a disk partition, was mounted on /home. We are unmounting it, and locating the home directories in the /home directory on the root filesystem, instead of on their own partition.
remove /home from /etc/fstab...
note: if you are going to add a different logical volume, skip removing it from fstab. We will just edit it for the new name.
vi /etc/fstab
delete the
/dev/mapper/vg_hostname-lv_home /home ext4 defaults 1 2
line (arrow to the line and hit "dd")
save fstab
:x
make sure you have enough available space in the volume group for what you want to do...
[root@HOSTNAME ~]# vgs
VG #P #LV #SN Attr VSize VFree
vg_hostname 1 3 0 wz--n- 1.80t 1.50t
delete the logical volume:
lvremove /dev/mapper/vg_hostname-lv_home
Note: it is possible to increase the size of a filesystem when it is mounted, but not to decrease it. This is significant if you need to resize the root filesystem. To decrease the size of the root filesystem, you must boot into single user mode. We are increasing the size of the root filesystem, so we are ok in multi user mode.
increase the root logical volume to 300 GB...
lvextend -L 300G /dev/mapper/vg_hostname-lv_root
lvextend said it worked, but I don't see the new size in a df -- that is because I also need to resize the filesystem. Had I remembered, I could have run...
lvextend -L 300G -r /dev/mapper/vg_hostname-lv_root
where the '-r' flag causes lvextend to automatically resize the filesystem as well.
I can run the resize2fs program to fix it, though...
resize2fs /dev/mapper/vg_hostname-lv_root
which will probably take a few minutes.
if you do a df after resize2fs finishes, you should see 300 GB assigned to the root filesystem.
if we were just deleting /home and giving some extra disk space to root, we are done.
to add a new logical volume of one terabyte called lv_data...
lvcreate -L 1T -n lv_data vg_hostname
to format the new logical volume with an ext4 filesystem...
mkfs.ext4 /dev/mapper/vg_hostname-lv_data
add a directory to mount the new filesystem on...
mkdir /data
revisit /etc/fstab, and change this line...
/dev/mapper/vg_hostname-lv_home /home ext4 defaults 1 2
to this...
/dev/mapper/vg_hostname-lv_data /data ext4 defaults 1 2
when the system is booted, the init scripts read through fstab and try to mount the drives configured therein. You can turn this off by changing "defaults" to "noauto", but that seems undesirable in this case. "noauto" is more often used with remote nfs or Windows filesystems that might be inaccessible at boot time.
make sure you can mount the drive, and validate your fstab entry...
mount /data
afterwards, a df should look something like this...
[root@HOSTNAME ~]# df -H
Filesystem Size Used Available Use% Mounted on
/dev/mapper/vg_hostname-lv_root
300G 30G 270G 10% /
tmpfs 4G .10G 3.90G 1% /dev/shm
/dev/sda3 .5G .1G .4G 20% /boot
/dev/mapper/vg_hostname-lv_data
1.0T .1T .9T 10% /data
