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. Utilizing the device mapper Linux kernel framework, the current iteration, LVM2, can be used to gather existing storage devices into groups and allocate logical units from the combined space as needed.
In this guide, we will cover how to manage your storage devices with LVM. We will show you how to display information about volumes and potential targets, how to create and destroy volumes of various types, and how to modify existing volumes through resizing or transformation.
We will be using an Ubuntu In order to follow along, you should have access to an Ubuntu You will need to have a non-root user with sudo privileges configured for administrative tasks.
You can follow our Ubuntu It is important to be able to get information about the various LVM components in your system easily. Fortunately, the LVM tool suite provides an abundant amount of tools for displaying information about every layer in the LVM stack. To display all of the available block storage devices that LVM can potentially manage, use the lvmdiskscan command:.
A header is written to storage devices to mark them as free to use as LVM components. Devices with these headers are called physical volumes. You can display all of the physical devices on your system by using lvmdiskscan with the -l option, which will only return physical volumes:. The pvscan command is fairly similar to the above, in that it searches all available devices for LVM physical volumes.
The output format is a bit different and it include a small amount of additional information:. If you need more detail, the pvs and pvdisplay commands are better options.
The pvs command is highly configurable and can display information in many different formats. Because its output can be tightly controlled, it is frequently used in when scripting or automation is needed.
Its basic output provides a useful at-a-glance summary similar to the earlier commands:. For more verbose, human-readable output, the pvdisplay command is usually a better option:.
As you can see the pvdisplay command is often the easiest command for getting detailed information about physical volumes.
To discover the logical extents that have been mapped to each volume, pass in the -m option to pvdisplay :. This can be very useful when trying to determine which data is held on which physical disk for management purposes.
The vgscan command can be used to scan the system for available volume groups. It also rebuilds the cache file when necessary. It is a good command to use when you are importing a volume group into a new system:. The command does not output very much information, but it should be able to find every available volume group on the system.
To display more information, the vgs and vgdisplay commands are available. Like its physical volume counterpart, the vgs command is versatile and can display a large amount of information in a variety of formats. Because its output can be manipulated easily, it is frequently used in when scripting or automation is needed.
For example, some helpful output modifications are to show the physical devices and the logical volume path:. For more verbose, human-readable output, the vgdisplay command is a usually the best choice. Adding the -v flag also provides information about the physical volumes the volume group is built upon, and the logical volumes that were created using the volume group:. The vgdisplay command is useful because it can tie together information about many different elements of the LVM stack.
As with the other LVM components, the lvscan option scans the system and outputs minimal information about the logical volumes it finds:. 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.
You might also want to try the lvs and pvs commands, which list the Logical Volumes and Physical Volumes respectively, and their more detailed variants; lvdisplay and pvdisplay.
If you are doing this from the desktop livecd, once you have created your Logical Volumes from the terminal, you can run the installer, and use manual partitioning to select how to use each Logical Volume , and then install.
The space is allocated from any free space anywhere in the bar Volume Group. If you have multiple Physical Volumes you can add the names of one or more of them to the end of the command to limit which ones should be used to satisfy the request. After extending the Logical Volume you need to expand the filesystem to use the new space. If you only have one other Physical Volume , then that is where it will be moved to, or you can add the name of one or more specific Physical Volumes that should be used to satisfy the request, instead of any Physical Volume in the Volume Group with free space.
This process can be resumed safely if interrupted by a crash or power failure, and can be done while the Logical Volume s in question are in use. You can also add -b to perform the move in the background and return immediately, or -i s to have it print how much progress it has made every s seconds. If you background the move, you can check its progress with the lvs command. Snapshots When you create a snapshot, you create a new Logical Volume to act as a clone of the original Logical Volume.
The snapshot volume initially does not use any space, but as changes are made to the original volume, the changed blocks are copied to the snapshot volume before they are changed, in order to preserve them. This means that the more changes you make to the origin, the more space the snapshot needs. Active Oldest Votes. Other nice features that LVM "Logical Volumes" provide are: If you have more than one hard-disk, Logical Volumes can extend over more than one disk: i.
Downsides Of course, all of this comes at a price: the initial setup of LVM is more complex than just partitioning a disk, and you will definitely need to understand the LVM terminology and model Logical Volumes, Physical Volumes, Volume Groups before you can start using it. Also, if you use LVM across hard drives, you may lose all your data when only one drive fails.
Improve this answer. Michael Laszlo 2 2 bronze badges. Riccardo Murri Riccardo Murri With LVM2 you can also set up writeable snapshots too! Basically, LVM takes complicated things and makes them possible, but takes already possible things and makes them more complicated. The short answer is that increasing the size of a partition on the disk is a pain. Michael Kubler Michael Kubler 4 4 silver badges 2 2 bronze badges.
Abhinav Abhinav 1 1 silver badge 3 3 bronze badges. Yes it's just a personal server, so it sounds like I won't be needing it. Late, but still. So yes, if you have a situation when you have installer on more than one partition, you should have a look att LVM. It isn't that hard to understand actually. Volume group are same has a hard disk. Logical volume are the same as a partition and Physical volumes are the partitions that you build the Volume group on.
LVM adds a lot of complexity. I left it enabled by default on my small server and now have a confusing situation with all these logical volumes not being set up the way I want, and now I have to go research how to fix this Bananeweizen Bananeweizen 2 2 gold badges 14 14 silver badges 20 20 bronze badges.
Really self-defeating and destructive logic. People need to learn what's possible so they can decide what they need. It is recommended good practice that any partition used by lvm is marked as type 8e.
But still we have no information about the lvm's logical volume layout or the way that physical volumes map to the logical volumes. As you may have guessed from the above fdisk and gparted screenshots, these tools do not yet have the functionality to identify any logical volumes.
They can only identify that a given partition is being used by the logical volume manager. Below is a screenshot from a handy graphical tool which you can use to view all logical and physical volumes.
As you can see from the text on the right of the screenshot, there is one volume group called ubuntu. By clicking on the volumes under "physical view" and "logical view", you can see more information about each physical and logical volumes respectively. The above tool which can be quite handy is called system-config-lvm. To install it if you're using a laptop or desktop:. You can also use this tool to perform your lvm actions for you. However, it does not recognise raid properly, so could mislead people using raid.
To properly understand how to administer lvm, you really ought to know how to use the command line tools which are packaged as lvm2 and already included in a Ubuntu Having said that you can get most jobs done using the system-config-lvm gui. An interesting thing to point out about the default Ubuntu This is a good time to point out where you can find the logical volumes on your filesystem or rather what to call them when you need to reference them. If you do an "ls -la" on these, you'll see they both point to the same underlying block device.
Lets start out at the command line by introducing the three main display commands: pvdisplay, vgdisplay, and lvdisplay. To see what physical volumes are configured for lvm, use the pvdisplay command. When used with its " -m " option, you can also see the range of physical extents and how they map to logical extents. As we described earlier, a volume group manages a pool of physical extents and the logical volumes you've built from them. To see details about the volume groups that exist on your system, use the vgdisplay command:.
Note that to only see the info about a specific volume group or groups, just include the name s as part of the command, e. Finally, if you'd like to display the logical volumes on your system, use the lvdisplay command.
You have two choices when choosing how to add physical disk space to logical volume management.
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