LVM

Logical Volume Manager

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LVM (Logical Volume Manager) Logical Volume Manager

The point of LVM is to elastically adjust the capacity of the file system!

LVM can consolidate multiple physical partitions together, making these partitions look like a single disk.

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PV (Physical Volume) physical volume

Create PV

[root@localhost ~]# pvcreate /dev/sdb /dev/sdc

Query PV

[root@localhost ~]# pvs
[root@localhost ~]# pvscan
[root@localhost ~]# pvdisplay

delete PV

[root@localhost ~]# pvremove /dev/sdc

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VG (Volume Group) volume group

vgcreate #New VG
vgscan #Query VG
vgdisplay #Display VG
vgextend #Add extra PV
in VG vgreduce #Delete PV in VG
vgchange #Set whether VG is active (active)
vgremove #Delete a VG

vgcreate -s 4M [VG_volume group name] [PV_physical volume name/dev/sdb1] #Create VG

[root@localhost ~]# vgcreate -s 4M my_vg /dev/sdb /dev/sdc

vgextend [VG_volume group name] [PV_physical volume name] #Add a single VG

[root@localhost ~]# vgextend my_vg /dev/sdc

 

vgreduce [VG_volume group name] [PV_physical volume name] #Remove a single VG

vgreduce my_vg /dev/sdc

 

vgremove [VG_volume group] #Remove the entire VG volume group

[root@localhost ~]# vgremove my_vg

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LV (Logical Volume) logical volume

lvcreate #Create LV
lvscan #Query LV
lvdisplay #Display LV
lvextend
#Increase capacity in LV lvreduce #Reduce capacity in LV
lvremove #Delete an LV lvresize #Adjust
the capacity of LV

 

Creation of LV

lvcreate -L [how much space to allocate] -n [specify LV name] [from which VG volume group to divide]

[root@localhost ~]# lvcreate -L 10G -n my_lv my_vg

[root@localhost ~]# mkfs.ext4 /dev/my_vg/my_lv

LV expansion

lvextend -L [how much space to allocate] [logical volume]

[root@localhost ~]# lvextend -L +5G /dev/my_vg/my_lv

[root@localhost ~]# resize2fs -f /dev/my_vg/my_lv

 

LV reduction

[root@localhost ~]# umount /dev/my_vg/my_lv #Unmount the logical volume

[root@localhost ~]# e2fsck -f /dev/my_vg/my_lv #Check the file system

resize2fs -f /dev/my_vg/my_lv [reduced file size]

[root@localhost ~]# resize2fs -f /dev/my_vg/my_lv 10G #Reduce the file system first

lvreduce -L [reduced file size] /dev/my_vg/my_lv

[root@localhost ~]# lvreduce -L 10G /dev/my_vg/my_lv #Reduce the logical volume

 

LV snapshot function

[root@localhost ~]# lvcreate -s -n mylv_back -L 200M /dev/my_vg/my_lv

-s #Indicates to take a snapshot
-n #Snapshot name (here mylv_back)
-L #Specify snapshot size (200M)
/dev /my_vg/my_lv #Take a snapshot of this device

[root@localhost ~]# mount /dev/my_vg/mylv_back /ghost/ #Data comes back after mounting

[root@localhost /]# lvremove /dev/my_vg/mylv_back #Uninstall snapshot

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