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** <code>vgs</code> - display compact information about all volume groups
** <code>vgdisplay</code> - display verbose information about all volume groups
** <code>vgcreate</code> - creates a new volume group. Usually, only one volume group is used per system, but additional ones can be created in special circumstances. You must specify at least one PV to create a LVVG.** <code>vgextend</code> - adds additional PVs to an LVa VG.** <code>vgreduce</code> - removes PVs from an LVa VG.** <code>vgremove</code> - destroys an LVa VG.
* LV management
** <code>lvs</code> - display compact information about all logical volumes
{{Admon/note|Using LVM in Fedora's Rescue Mode|The Fedora installation DVD has a "rescue mode" which may be used to fix problems on a previously-installed system -- useful if (for example) you have deleted or messed up a file that is necessary to successfully boot the system. In rescue mode, only a single LVM command is available: <code>lvm</code>. To use any of the lvm commands, you can type <code>lvm</code> followed by the name of the command you wish to execute. Alternately, typing <code>lvm</code> by itself will start the LVM shell, and you can then type any of the lvm commands directly. To use non-LVM commands, exit from the LVM shell.}}
== LVM Device Names ==
[[Category:Linux]][[Category:Fedora]][[Category:OPS235]][[Category:OPS335]]
PVs are referenced by their normal block device name, such as /dev/sda1. VGs and LVs are referred to by names which are assigned when they are created.
* as a virtual machine's storage device
Many LVM commands directly accept the LV name </code>(<code>vg_muskoka</code>) or the VG name and LV name separated by a slash (<code>vg_muskoka/lv_home</code>), but commands such as <code>mkfs</code> which are used with block devices require the full device name (<code>/dev/vg_muskoka/lv_home</code>)
== LVM and Booting ==
mount /dev/vg_muskoka/lv_archive /archive
# Edit /etc/fstab to have the filesystem file-system mounted automatically at boot time # (refer to [httphttps://wwwwiki.tuxfilesarchlinux.org/linuxhelpindex.php/fstab.html httphttps://wwwwiki.tuxfilesarchlinux.org/linuxhelpindex.php/fstab.html] for additional information) # Here is an example of how this can be performed)issuing a command to add the mount point to the bottom of the /etc/fstab file:<br /><br />echo "/dev/vg_muskoka/lv_archive /archive ext3 defaults 1 2" >>/etc/fstab
Notice that the LV serves as a container for the filesystemfile-system, but otherwise the two are independent. If you increase the size of the logical volume, you must then increase the size of the filesystem file-system so that it fills the logical volume:
# Add 5G to the logical volume lv_home:
lvextend vg_muskoka/lv_home -r --size +5G
When reducing the size of an LV-based filesystem, it's critical that you shrink the filesystem (the contents) before you shrink the LV (the container) -- otherwise you may lose data, and the filesystem will be damaged. Here is an example:
# Reduce the filesystem in lv_home by 5G
resize2fs /dev/vg_muskoka/lv_home -5G50G
# Shrink the LV:
lvreduce vg_muskoka/lv_home --size -5G
# or specify an absolute size of 50G<br /><br />Note: If you are experiencing problems mounting the reduced LV, it may be due to the difference in extent size<br /> between the LINV and the filesystem layer. To fix this problem,<br /> remove the LV, create, format the LV, and then resize only using the lvreduce command with the -r option.<br /> This automatically reduces the filesystem , and the LV.<br /> Refer to this example below"<br /><br />lvreduce -r vg_muskoka/lv_home --size 50G
{{Admon/important|Check your arguments!|lvreduce and lvextend can both take absolute or relative size arguments. For example, <code>-5G</code> means "reduce the size by five gigabytes", but <code>5G</code> means "make the size five gigabytes". If you have a 100G LV, the command <code>lvresize vg_muskoka/lv_home --size -5G</code> would shrink it to 95G, but accidentally typing <code>lvresize vg_muskoka/lv_home --size 5G</code> would shrink it to 5G. This would cause data loss if you have previously resized the filesystem to 95G. Remember to check your commands carefully.}}
{{Admon/important|Check your arguments!Non-integer sizes|lvreduce, lvextend, and resize2fs can all take absolute or relative size argumentsThe LVM commands accept fractional sizes such as 1. For example, <code>-5G</code> means "reduce the size by five gigabytes", but <code>5G</code> means "make the size five gigabytes". If resize2fs does not -- so you have a 100G LV, must use the command <code>lvresize vg_muskoka/lv_home next--size -5G</code> would shrink it to 95Gsmallest unit. For example, but accidentally typing <code>lvresize vg_muskoka/lv_home --size 5G</code> would shrink it to 1.5G. This would cause data loss if you have previously resized the filesystem corresponds to 95G1536M (1. Remember to check your commands carefully5 * 1024M).}}
Remember the order in which the filesystem and LV size must be adjusted:
If a system is installed with all of the VG space in use, it will be necessary to add a PV or reduce the size of an LV in order to add any more LVs or to grow one of the existing LVs. '''It's therefore a much better idea to create small LVs initially, leaving some unused space in the VG which can be assigned as needed'''.
=== Adding a Physical Volume ===
To add a physical volume to the system:
# Add the disk (if not already attached) -- for this example, let's assume the disk is <code>/dev/sdb</code>
# Create a partition with <code>fdisk</code> - let's assume the partition is <code>/dev/sdb1</code>
# Mark the partition as usable by LVM: <code>pvcreate /dev/''sdb1''</code>
# Add the partition to your volume group: <code>vgextend vg_main /dev/''sdb1''</code>
