LVM: Difference between revisions

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The Logical Volume Manager (LVM) provides means to dynamically organize partitions.

[https://en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux) The Logical Volume Manager] (LVM) provides means to dynamically organize partitions.

== Basic Setup ==

LVM manages three types:

* physical volumes - directly on a ~~physical~~ partition

; Physical volume (PV) : Space reservation consisting of a disk partition, a whole disk, a meta device, or a loopback file.

* volume groups - a group of physical volumes

; Volume group (VG) : Group of physical volumes.

* logical volumes

; Logical volume (LV) : Space reservation inside a volume group, which may be laid across multiple physical volumes.

=== Create a logical volume ===

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# creates a new logical volume named "home" with the size of 10GB (check with lvdisplay)

# makes /dev/pool/home available

lvcreate -L 10G -n home pool

lvcreate --size 10G --name home pool

mkfs.ext4 /dev/pool/home

</syntaxHighlight>

=== Use the Logical Volume ===

in your `configuration.nix`:

in your <code>configuration.nix</code>:

fileSystems."/home" = {

device = "/dev/pool/home";

fsType = "ext4";

}

};

</syntaxHighlight>

== ~~Special~~ LVM Modes ==

LVM provides a number of special features such as creating snapshots, raid for single Logical Volumes and much more. If you want to use these devices on bootup, the associated <code>dm-*</code> kernel module must be provided in the initrd (see for example {{Issue|33646}}) . This is a non-exhaustive list of features and the corresponding kernel module to put into your <~~pre~~>configuration.nix</~~pre~~>:

== Booting with special LVM Modes ==

LVM provides a number of special features such as creating snapshots, raid for single Logical Volumes and much more. If you want to use these devices on bootup, the associated <code>dm-*</code> kernel module must be provided in the initrd (see for example {{Issue|33646}}) . This is a non-exhaustive list of features and the corresponding kernel module and other options to put into your <code>configuration.nix</code>:

boot.initrd.kernelModules = [

"dm-snapshot" # when you are using snapshots

"dm-raid" # e.g. when you are configuring raid1 via: `lvconvert -m1 /dev/pool/home`

"dm-cache-default" # when using volumes set up with lvmcache

];

services.lvm.boot.thin.enable = true; # when using thin provisioning or caching

</syntaxHighlight>

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=== Disko ===

Disko provides means to automatically generate the creation and configuration of logical volumes, see ~~http~~://~~cgit~~.~~lassul.us~~/disko~~/tree/README.md .~~

[[Disko]] provides means to automatically generate the creation and configuration of logical volumes, see https://github.com/nix-community/disko

[[Category:Filesystem]]

@@ Line 1: / Line 1: @@
-The Logical Volume Manager (LVM) provides means to dynamically organize partitions.
+[https://en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux) The Logical Volume Manager] (LVM) provides means to dynamically organize partitions.
 == Basic Setup ==
 LVM manages three types:
-* physical volumes - directly on a physical partition
+; Physical volume (PV) : Space reservation consisting of a disk partition, a whole disk, a meta device, or a loopback file.
-* volume groups - a group of physical volumes
+; Volume group (VG) : Group of physical volumes.
-* logical volumes
+; Logical volume (LV) : Space reservation inside a volume group, which may be laid across multiple physical volumes.
 === Create a logical volume ===
@@ Line 16: / Line 17: @@
 # creates a new logical volume named "home" with the size of 10GB (check with lvdisplay)
 # makes /dev/pool/home available
-lvcreate -L 10G -n home pool
+lvcreate --size 10G --name home pool
 mkfs.ext4 /dev/pool/home
 </syntaxHighlight>
 === Use the Logical Volume ===
-in your `configuration.nix`:
+in your <code>configuration.nix</code>:
 <syntaxHighlight lang=nix>
- fileSystems."/home" = {
+fileSystems."/home" = {
    device = "/dev/pool/home";
    fsType = "ext4";
-}
+};
 </syntaxHighlight>
-== Special LVM Modes ==
-LVM provides a number of special features such as creating snapshots, raid for single Logical Volumes and much more. If you want to use these devices on bootup, the associated <code>dm-*</code>  kernel module must be provided in the initrd (see for example {{Issue|33646}}) . This is a non-exhaustive list of features and the corresponding kernel module to put into your <pre>configuration.nix</pre>:
+== Booting with special LVM Modes ==
+LVM provides a number of special features such as creating snapshots, raid for single Logical Volumes and much more. If you want to use these devices on bootup, the associated <code>dm-*</code>  kernel module must be provided in the initrd (see for example {{Issue|33646}}) . This is a non-exhaustive list of features and the corresponding kernel module and other options to put into your <code>configuration.nix</code>:
 <syntaxHighlight lang=nix>
 boot.initrd.kernelModules = [
    "dm-snapshot" # when you are using snapshots
    "dm-raid" # e.g. when you are configuring raid1 via: `lvconvert -m1 /dev/pool/home`
+  "dm-cache-default" # when using volumes set up with lvmcache
 ];
+services.lvm.boot.thin.enable = true; # when using thin provisioning or caching
 </syntaxHighlight>
@@ Line 45: / Line 50: @@
 === Disko ===
-Disko provides means to automatically generate the creation and configuration of logical volumes, see http://cgit.lassul.us/disko/tree/README.md .
+[[Disko]] provides means to automatically generate the creation and configuration of logical volumes, see https://github.com/nix-community/disko
+[[Category:Filesystem]]