Installation guide
Table Of Contents
- LVM Administrator's Guide
- Table of Contents
- Introduction
- Chapter 1. The LVM Logical Volume Manager
- Chapter 2. LVM Components
- Chapter 3. LVM Administration Overview
- Chapter 4. LVM Administration with CLI Commands
- 1. Using CLI Commands
- 2. Physical Volume Administration
- 3. Volume Group Administration
- 3.1. Creating Volume Groups
- 3.2. Adding Physical Volumes to a Volume Group
- 3.3. Displaying Volume Groups
- 3.4. Scanning Disks for Volume Groups to Build the Cache File
- 3.5. Removing Physical Volumes from a Volume Group
- 3.6. Changing the Parameters of a Volume Group
- 3.7. Activating and Deactivating Volume Groups
- 3.8. Removing Volume Groups
- 3.9. Splitting a Volume Group
- 3.10. Combining Volume Groups
- 3.11. Backing Up Volume Group Metadata
- 3.12. Renaming a Volume Group
- 3.13. Moving a Volume Group to Another System
- 3.14. Recreating a Volume Group Directory
- 4. Logical Volume Administration
- 4.1. Creating Logical Volumes
- 4.2. Persistent Device Numbers
- 4.3. Resizing Logical Volumes
- 4.4. Changing the Parameters of a Logical Volume Group
- 4.5. Renaming Logical Volumes
- 4.6. Removing Logical Volumes
- 4.7. Displaying Logical Volumes
- 4.8. Growing Logical Volumes
- 4.9. Extending a Striped Volume
- 4.10. Shrinking Logical Volumes
- 5. Creating Snapshot Volumes
- 6. Controlling LVM Device Scans with Filters
- 7. Online Data Relocation
- 8. Activating Logical Volumes on Individual Nodes in a Cluster
- 9. Customized Reporting for LVM
- Chapter 5. LVM Configuration Examples
- Chapter 6. LVM Troubleshooting
- Chapter 7. LVM Administration with the LVM GUI
- Appendix A. The Device Mapper
- Appendix B. The LVM Configuration Files
- Appendix C. LVM Object Tags
- Appendix D. LVM Volume Group Metadata
- Index
al extents.
lvreduce -l -3 vg00/lvol1
5. Creating Snapshot Volumes
Use the -s argument of the lvcreate command to create a snapshot volume. A snapshot
volume is writeable.
LVM snapshots are not cluster-aware, so they require exclusive access to a volume. For inform-
ation on activating logical volumes on individual nodes in a cluster, see Section 8, “Activating
Logical Volumes on Individual Nodes in a Cluster”.
The following command creates a snapshot logical volume that is 100 megabytes in size named
/dev/vg00/snap. This creates a snapshot of the origin logical volume named /dev/vg00/lvol1. If
the original logical volume contains a file system, you can mount the snapshot logical volume on
an arbitrary directory in order to access the contents of the file system to run a backup while the
original file system continues to get updated.
lvcreate --size 100M --snapshot --name snap /dev/vg00/lvol1
After you create a snapshot logical volume, specifying the origin volume on the lvdisplay com-
mand yields output that includes a a list of all snapshot logical volumes and their status (active
or inactive).
The following example shows the status of the logical volume /dev/new_vg/lvol0, for which a
snapshot volume /dev/new_vg/newvgsnap has been created.
# lvdisplay /dev/new_vg/lvol0
--- Logical volume ---
LV Name /dev/new_vg/lvol0
VG Name new_vg
LV UUID LBy1Tz-sr23-OjsI-LT03-nHLC-y8XW-EhCl78
LV Write Access read/write
LV snapshot status source of
/dev/new_vg/newvgsnap1 [active]
LV Status available
# open 0
LV Size 52.00 MB
Current LE 13
Segments 1
Allocation inherit
Read ahead sectors 0
Block device 253:2
The lvs command, by default, displays the origin volume and the current percentage of the
snapshot volume being used for each snapshot volume. The following example shows the de-
fault output for the lvs command for a system that includes the logical volume /
dev/new_vg/lvol0, for which a snapshot volume /dev/new_vg/newvgsnap has been created.
# lvs
LV VG Attr LSize Origin Snap% Move Log Copy%
lvol0 new_vg owi-a- 52.00M
newvgsnap1 new_vg swi-a- 8.00M lvol0 0.20
5. Creating Snapshot Volumes
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