But, we are using LVM so we need to run some additional commands to use the new disk space. The first thing we need to do is resize the physical volume. We can view the size of the physical volumes using the command pvdisplay. How to resize an LVM root partition. Tags: Linux administration. Linux servers. But although pvresize's output tells me that the volume was resized, it keeps showing the same size, so I must be missing something. (type L to list codes): 8e Changed system type of partition 3 to 8e (Linux LVM) Command (m for.
Here we show you how to shrink an LVM volume or partition in Linux by first resizing the file system followed by resizing the logical volume. See here if you’re instead trying to do the opposite.
Note: In this example we are working in CentOS 7, some commands may differ in different Linux distributions. As of CentOS 7 the default file system is XFS which is not currently possible to shrink, this example is working with the ext4 file system. In this example we will work through shrinking logical volume /var/centos/var from 10GB to 5GB. Overview of Logical Volume Manager (LVM) Before working through the resizing process it’s important you first understand some basic concepts around physical volumes, volume groups, logical volumes, and the file system. Physical Volume (PV): This can be created on a whole physical disk (think /dev/sda) or a Linux partition. Volume Group (VG): This is made up of at least one or more physical volumes.
Logical Volume (LV): This is sometimes referred to as the partition, it sits within a volume group and has a file system written to it. File System: A file system such as ext4 will be on the logical volume. LVM Resize – How to decrease or shrink the logical volume To decrease the size of an LVM partition you must first decrease the file system within in order to avoid possible data corruption.
As there is the potential for this to happen if you enter the command incorrectly, it is strongly recommended that you have a full backup of your data before proceeding. Shrinking a logical volume will give you more space in the volume group, meaning that you could instead with this new found space. The first step will depend on if you’re looking to shrink a LVM root volume, or non-root volume.
Shrinking a root volume The root volume would typically be the logical volume that is mounted to /. You cannot unmount this to shrink it as it’s in use by the running operating system meaning that you will have to first boot from a Live CD to complete this. Once booted into the Live CD, you may first need to run the below command to pick up LVM volumes, however this usually happens during boot so may not be required, if in doubt just run it.
Vgchange -a y Shrinking a non-root volume Alternatively if the volume you are shrinking is a non-root volume, that is any other volume not mounted to the root of the file system, you can unmount the volume as shown below to proceed. Please note that when you unmount the volume the data will not be available, so you may need to schedule down time and stop running applications that use data from it prior to unmounting. Unmount by specifying either the logical volume or the location it’s currently mounted to, in the below example we specify the logical volume which can be found in /dev/(vg-name)/(lv-name).
Umount /dev/centos/var All following steps now apply to both a root or non-root volume. Before being able to attempt to shrink the size of an LVM volume, you must first run a file system check on it. If you don’t do this, you will get an error message and will not be able to proceed. This is a required step as resizing a file system in a bad state could cause data corruption. The -f flag makes the check run even if the file system appears clean, while -y assumes yes to all questions and will respond if asked to fix a problem. E2fsck -fy /dev/centos/var Next you need to shrink the file system, to be safe we’re going to shrink the file system lower than what the logical volume will shrink to. This is because we don’t want to accidentally shrink the logical volume to a size lower than the file system in the next step, as this can result in corruption and data loss.
Don’t worry, we’ll reclaim the space at the end. The command below will shrink the file system so that it is only 4G in size total, note that what ever size you specify to shrink to you must have in free space within the file system otherwise you must first delete data. Resize2fs /dev/centos/var 4G Once the file system has been reduced, we can shrink the size of the logical volume with the lvreduce command. Reduce this to the size that you want the volume to be, as specified by the -L flag. Instead if you want to reduce by a specified size, simply put a – in front of the size.
Both are shown below for completeness, however you only need to run one. To reduce to 5G lvreduce -L 5G /dev/vg/disk-name To reduce by 5G lvreduce -L -5G /dev/vg/disk-name Once you execute the lvreduce command you will get a warning advising the size you have chosen to reduce to so use this as a chance to confirm you’re shrinking the logical volume to a size that is NOT smaller than the size you previously shrunk the file system to. Once you have confirmed it’s fine to proceed enter ‘y’ and press enter. After the logical volume has been lowered to the required size, run resize2fs on the volume as this will extend the file system to use all available space within the logical volume.
This makes use of all remaining free space so that none is wasted from when we previously shrunk the file system to a lower size than the logical volume. Resize2fs /dev/centos/var At this point all that’s left to do is mount the volume. If this was a root volume and you’re working within a Live CD, simply boot back into your primary Linux operating system.
If this was a non-root volume and you unmounted it to complete the reduction, simply mount it back. You can do this with ‘mount -a’ assuming you have the configuration already set in /etc/fstab, otherwise specify the logical volume and where it should mount to. Here we’re manually mounting to /mnt just for testing. Mount /dev/centos/var /mnt After you’ve either booted back to primary operating system or completed the mount, check the space shown with the ‘df’ command to confirm it has been decreased as expected. /# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/centos-root 9.8G 1.4G 8.5G 14% / devtmpfs 908M 0 908M 0% /dev tmpfs 914M 0 914M 0% /dev/shm tmpfs 914M 8.6M 905M 1% /run tmpfs 914M 0 914M 0% /sys/fs/cgroup /dev/sda1 497M 96M 402M 20% /boot /dev/mapper/centos-var 4.8G 20M 4.6G 1% /mnt In this example /dev/centos/var is correctly showing as shrunk down from the original 10G. Summary We have now successfully shrunk a file system and corresponding LVM logical volume. Root volumes can only be shrunk by unmounting the file system which requires booting into a Live CD to complete the work.
For non-root volumes the file system must first be unmounted so that you can shrink the volume. First the file system was checked, then reduced.
![How to shrink a default install lvm pvresize command system How to shrink a default install lvm pvresize command system](http://www.server-world.info/en/Fedora_15/install/img/16.jpg)
The logical volume itself was then reduced. It is strongly recommended to have a backup before attempting this to avoid data loss through mistakes.
Extend/Reduce LVMs in Linux Requirements. When do we need to reduce volume? May be we need to create a separate partition for any other use or we need to expand the size of any low space partition, if so we can reduce the large size partition and we can expand the low space partition very easily by the following simple easy steps. My Server Setup – Requirements. Operating System – CentOS 6.5 with LVM Installation. Server IP – 192.168.0.200 How to Extend Volume Group and Reduce Logical Volume Logical Volume Extending Currently, we have One PV, VG and 2 LV.
Let’s list them one by one using following commands. # pvs # vgs # lvs. Logical Volume Extending There are no free space available in Physical Volume and Volume group.
So, now we can’t extend the lvm size, for extending we need to add one physical volume ( PV), and then we have to extend the volume group by extending the vg. We will get enough space to extend the Logical volume size. So first we are going to add one physical volume. For adding a new PV we have to use fdisk to create the LVM partition.
# fdisk -cu /dev/sda. To Create new partition Press n. Choose primary partition use p. Choose which number of partition to be selected to create the primary partition. Press 1 if any other disk available. Change the type using t.
Type 8e to change the partition type to Linux LVM. Use p to print the create partition ( here we have not used the option). Press w to write the changes.
Restart the system once completed. Verify Resize Partition. New Physical Volume added.
Volume group vgtecmint extended from 17.51GB to 35.50GB. Logical volume LogVol01 extended from 16.51GB to 34.50GB. Here we have completed the process of extending volume group and logical volumes. Let us move towards some interesting part in Logical volume management.
Reducing Logical Volume (LVM) Here we are going to see how to reduce the Logical Volumes. Everyone say its critical and may end up with disaster while we reduce the lvm. Reducing lvm is really interesting than any other part in Logical volume management. Before starting, it is always good to backup the data, so that it will not be a headache if something goes wrong. To Reduce a logical volume there are 5 steps needed to be done very carefully. While extending a volume we can extend it while the volume under mount status (online), but for reduce we must need to unmount the file system before reducing. Let’s wee what are the 5 steps below.
unmount the file system for reducing. Check the file system after unmount. Reduce the file system.
Reduce the Logical Volume size than Current size. Recheck the file system for error. Remount the file-system back to stage. For demonstration, I have created separate volume group and logical volume. Here, I’m going to reduce the logical volume tecmintreducetest. Now its 18GB in size.
We need to reduce it to 10GB without data-loss. That means we need to reduce 8GB out of 18GB. Already there is 4GB data in the volume.
18GB - 10GB While reducing size, we need to reduce only 8GB so it will roundup to 10GB after the reduce. What is the difference between L and l (small)? L = Can be used while MB, GB or TB in size l = Can be used while resizing or reducing with Physical extent in size (PE), (The default extent size of a single PE is 4 MB). What is the difference between LVresize and LV extent? Lvresize = Take an example resizing from 10 GB to 20 GB using existing PEs from the Volume group.
Lvextend = Only used while adding a new device (/dev/sdc or /dev/sdd or whatever ) to existing volume group. Thanks & Regards, Bobin Lonston. I tried reducing the LV on a test system. Worked like breeze. To calculate the PE’s to remove I converted everything to real bytes. That is, PE size of 4MiB = 4.
1024. 1024. And the number of GB to remove was 1Gib = 1024. 1024. 2014 bytes.
After resizefs, the space needed by the file system is specified in 4kiB blocks, so 4096 bytes each. If you want to calculate accurately without losing a GB here and there AND you want to be sure not to reduce the LV beyond the size of the file system, I’d recommend this.