Create and remove physical volumes

5. Configure Local Storage

📘Red Hat Certified System Administrator (RHCSA – EX200)

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In Linux, when we manage storage using LVM (Logical Volume Manager), the physical volume (PV) is the starting point. A physical volume is essentially a hard disk, SSD, or partition that is prepared for use by LVM. Think of it as “raw storage space” that LVM can manage.

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1. Understanding Physical Volumes

• Physical Volume (PV): A disk or partition that has been initialized to work with LVM.
• Why use PVs: LVM allows you to combine multiple disks or partitions into one flexible storage system. PVs are the first step in this process.
• Commands to manage PVs: Linux provides commands like pvcreate, pvdisplay, pvremove to manage them.

Key point for the exam: You must know how to create, list, and remove PVs.

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2. Creating a Physical Volume

To create a physical volume, you use the command:

sudo pvcreate /dev/sdX

• /dev/sdX → Replace X with the actual disk or partition name.
• Example:

sudo pvcreate /dev/sdb1

This initializes /dev/sdb1 as a PV for LVM use.

Notes:

• The disk/partition must not contain any active data because pvcreate will overwrite the LVM metadata.
• After creation, the disk is ready to be added to a Volume Group (VG).

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Verify Physical Volume

After creating a PV, you can check it with:

pvdisplay

This shows details such as:

• PV Name (disk/partition)
• Volume Group (VG) it belongs to (if any)
• Size of the PV
• Free space

Or a simpler list with:

pvs

Example output of pvs:

PV         VG     Fmt  Attr PSize  PFree
/dev/sdb1  vg01   lvm2 a--  50.00g 50.00g

This tells you that /dev/sdb1 is a PV in VG vg01 and it has 50 GB free.

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3. Removing a Physical Volume

If you want to remove a PV from LVM, you need to make sure it’s not in use (not part of an active Volume Group or Logical Volume).

Steps to remove a PV:

1. Check if it’s in use:

pvs

2. Remove it from its Volume Group (if necessary):

vgreduce <VG_NAME> /dev/sdX

• <VG_NAME> → The Volume Group name
• /dev/sdX → The PV to remove

3. Remove the PV metadata:

pvremove /dev/sdX

Example:

sudo pvremove /dev/sdb1

This wipes the LVM metadata from the disk, making it a normal unallocated disk again.

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4. Important Exam Notes

1. Commands you must know:
   • Create PV: pvcreate /dev/sdX
   • List PVs: pvdisplay or pvs
   • Remove PV: pvremove /dev/sdX
2. Check usage before removal: Always verify that the PV is not part of any active VG or LV using pvs or vgdisplay.
3. Permissions: Most PV commands require sudo because you are modifying disks.
4. Disk requirements: The disk/partition must be empty or unmounted. LVM overwrites metadata, so never create PVs on disks with important data.

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5. Quick Workflow Example

1. Create a PV:

sudo pvcreate /dev/sdb1

2. Verify PV:

pvs

3. Add PV to Volume Group (for next step in LVM setup):

sudo vgcreate vg01 /dev/sdb1

4. Later, remove PV from VG:

sudo vgreduce vg01 /dev/sdb1

5. Remove PV completely:

sudo pvremove /dev/sdb1

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✅ Summary:

• PV = raw storage for LVM
• Use pvcreate to make it usable by LVM
• Use pvs or pvdisplay to check PV status
• Use pvremove to delete it after making sure it’s not in use