Snapshots This is something you simply can not do without LVM. It allows you to freeze an existing Logical Volume in time, at any moment, even while the system is running.
You can continue to use the original volume normally, but the snapshot volume appears to be an image of the original, frozen in time at the moment you created it. You can use this to get a consistent filesystem image to back up, without shutting down the system. You can also use it to save the state of the system, so that you can later return to that state if you mess things up.
You can even mount the snapshot volume and make changes to it, without affecting the original. The alternate installer has the ability to set up and install to LVM, and is the supported way of doing so. You can install the lvm2 package on an existing system, or the desktop livecd and manually set it up, and then install to it.
This is what I will cover. Ubuntu First, you need a Physical Volume. Typically you start with a hard disk, and create an LVM type partition on it. You can create one with gparted or fdisk, and usually only want one partition to use the whole disk, since LVM will handle subdividing it into Logical Volumes.
In gparted, you need to check the lvm flag when creating the partition, and with fdisk, tag the type with code 8e. I suggest you change foo to a name meaningful to you. Now you want to create a Logical Volume from some of the free space in foo : sudo lvcreate -n bar -L 5g foo This creates a Logical Volume named bar in Volume Group foo using 5 GB of space.
I currently have a Logical Volume for a Lucid install, and one for a Maverick install, so that is what I named those volumes. Although this type of problem may never have happened to you, running out of disk space while a critical program is running has happened to many people. And while many programs, especially Windows programs, are not as well written and resilient as VirtualBox, Linux Logical Volume Management made it possible to recover without losing any data and without having to restart the time-consuming installation.
The structure of a Logical Volume Manager disk environment is illustrated by Figure 1, below. That volume group can then be subdivided into logical volumes LV or used as a single large volume. In Figure 1, two complete physical hard drives and one partition from a third hard drive have been combined into a single volume group.
Two logical volumes have been created from the space in the volume group, and a filesystem, such as an EXT3 or EXT4 filesystem has been created on each of the two logical volumes.
Adding disk space to a host is fairly straightforward but, in my experience, is done relatively infrequently. The basic steps needed are listed below. You can either create an entirely new volume group or you can add the new space to an existing volume group and either expand an existing logical volume or create a new one. There are times when it is necessary to add a new logical volume to a host.
Now for the details. The following sequence is taken from an example I used as a lab project when teaching about Linux filesystems. This example shows how to use the CLI to extend an existing volume group to add more space to it, create a new logical volume in that space, and create a filesystem on the logical volume. This procedure can be performed on a running, mounted filesystem. If there is not enough space in the volume group on the existing hard drive s in the system to add the desired amount of space it may be necessary to add a new hard drive and create the space to add to the Logical Volume.
First, install the physical hard drive, and then perform the following steps. It is first necessary to create a new Physical Volume PV. It is not necessary to create a partition of any kind on the new hard drive. This creation of the Physical Volume which will be recognized by the Logical Volume Manager can be performed on a newly installed raw disk or on a Linux partition of type If you are going to use the entire hard drive, creating a partition first does not offer any particular advantages and uses disk space for metadata that could otherwise be used as part of the PV.
In this example we will extend an existing volume group rather than creating a new one; you can choose to do it either way. The command below creates a LV with a size of 50GB. Creating the Logical Volume does not create the filesystem.
That task must be performed separately. Adding a filesystem label makes it easy to identify the filesystem later in case of a crash or other disk related problems. You should also check to verify the volume has been created correctly. You can use the df , lvs, and vgs commands to do this. The need to resize a filesystem has been around since the beginning of the first versions of Unix and has not gone away with Linux.
It has gotten easier, however, with Logical Volume Management. This procedure can be used on a mounted, live filesystem only with the Linux 2. When a new hard drive is added to the system, it can be added to the volume group, and partitions that are logical volumes can be increased in size.
On the other hand, if a system is partitioned with the ext3 file system, the hard drive is divided into partitions of defined sizes. If a partition becomes full, it is not easy to expand the size of the partition. Community Control Panel. Hacktoberfest Contribute to Open Source. By Justin Ellingwood Published on September 14, Introduction LVM , or Logical Volume Management, is a storage device management technology that gives users the power to pool and abstract the physical layout of component storage devices for easier and flexible administration.
LVM Architecture and Terminology Before we dive into the actual LVM administrative commands, it is important to have a basic understanding of how LVM organizes storage devices and some of the terminology it employs. Physical Volumes : LVM utility prefix : pv Description : Physical block devices or other disk-like devices for example, other devices created by device mapper, like RAID arrays are used by LVM as the raw building material for higher levels of abstraction.
Physical volumes are regular storage devices. LVM writes a header to the device to allocate it for management. Volume Groups : LVM utility prefix : vg Description : LVM combines physical volumes into storage pools known as volume groups. Volume groups abstract the characteristics of the underlying devices and function as a unified logical device with combined storage capacity of the component physical volumes. Logical Volumes : LVM utility prefix : lv Description : A volume group can be sliced up into any number of logical volumes.
Logical volumes are functionally equivalent to partitions on a physical disk, but with much more flexibility. Logical volumes are the primary component that users and applications will interact with.
What are Extents? You can do this by typing: sudo lvmdiskscan The output will display all available block devices that LVM can interact with: Output. About the authors. Justin Ellingwood.
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