Basic command LVM

Logical Volume Management (LVM) is a powerful disk management tool in Linux that allows you to dynamically manage disk partitions and volumes. Here are some basic LVM commands:

1. Physical Volume (PV) Commands:

   • To create a physical volume: pvcreate /dev/sdX (Replace /dev/sdX with the actual device name.)

   • To display information about physical volumes: pvdisplay

   • To remove a physical volume from LVM: pvremove /dev/sdX

2. Volume Group (VG) Commands:

   • To create a volume group: vgcreate <vg_name> /dev/sdX (Replace <vg_name> with your chosen name and /dev/sdX with the PV.)

   • To display information about volume groups: vgdisplay

   • To extend a volume group: vgextend <vg_name> /dev/sdY (Add another PV to the existing VG.)

   • To reduce a volume group: vgreduce <vg_name> /dev/sdZ (Remove a PV from the VG.)

   • To remove a volume group: vgremove <vg_name>

3. Logical Volume (LV) Commands:

   • To create a logical volume within a VG: lvcreate -L <size> -n <lv_name> <vg_name> (Replace <size> with the size, <lv_name> with the LV name, and <vg_name> with the VG name.)

   • To display information about logical volumes: lvdisplay

   • To resize a logical volume: lvresize -L +<new_size> /dev/<vg_name>/<lv_name> (Increase the LV size.)

   • To remove a logical volume: lvremove /dev/<vg_name>/<lv_name>

   lvextend and lvresize are both commands used in Logical Volume Management (LVM) to change the size of a logical volume (LV), but they serve slightly different purposes:

   1. lvextend:

      • Purpose: The lvextend command is used to increase the size of a logical volume by adding more physical extents from the associated volume group (VG).

      • Usage Example: You would use lvextend when you want to make an LV larger by adding available space in the VG to it. For instance, when you add a new physical disk to the VG and want to use that space to expand an existing LV.

      • Command: lvextend -l +100%FREE /dev/<vg_name>/<lv_name> (This adds all available space from the VG to the LV.)

   2. lvresize:

      • Purpose: The lvresize command is used to change the size of a logical volume, either by shrinking or expanding it. It allows you to specify the new size explicitly, which can be larger or smaller than the current size.

      • Usage Example: You would use lvresize when you want to make precise changes to the LV's size, such as shrinking it to free up space in the VG or expanding it to a specific size.

      • Command: lvresize -L +<size> /dev/<vg_name>/<lv_name> (To increase the LV size by <size>.) OR lvresize -L -<size> /dev/<vg_name>/<lv_name> (To decrease the LV size by <size>.)

4. Other LVM Commands:

   • To activate all VGs: vgchange -ay

   • To deactivate a VG: vgchange -an <vg_name>

   • To activate an LV: lvchange -ay /dev/<vg_name>/<lv_name>

   • To deactivate an LV: lvchange -an /dev/<vg_name>/<lv_name>