LVM Resizing Overview

In our LVM Configuration KB, we showed how to create a linear mapped logical volume (LV).  In this KB, we are going to build on our LVM knowledge and show you how to resize an existing ext3 file system and it's associate LV.

Note: Procedures for resizing XFS, ResierFS and other volumes may differ.  You should check your documentation for non ext3 volumes before proceeding.  Resizing a file system can also be destructive if not done properly.  You should always make sure you have a backup of your data before attempting a resize!

Logical Volumes can be increased or decreased in size depending on your needs.  However, resizing the LV does not eliminate the need to resize the file system contained within the LV.  This is an important concept to understand since resizing the LV without resizing the file system can cause corruption of your data.

In the following pages, we will guide you through expanding and contracing LV's and their associated file systems.  Let's get to it!

Grow File System

Increasing the size of a file system managed with LVM can be done online (with the file system mounted.)  In order to grow the LV and file system:

• Check to see if free space exists on the LV that contains the file system
• Expand the LV if it does not contain enough free space (which could require expanding the volume group if it is out of free space)
• Grow the file system to utilize all available space on the LV

1. First, check the size of the file system to see if it needs expanding
   
   

   [root@Linux01 ~]# pwd /TCPDumpLV [root@Linux01 TCPDumpLV]# df -kh . Filesystem Size Used Avail Use% Mounted on /dev/mapper/TCPDumpVolGRP-TCPDumpLV 3.1G 2.9G 69M 98% /TCPDumpLV

   Note: The disk free command shows that we have 65MB available on our file system and that its 98% use.  If we don't take action soon, we risk filling the file system.
   
   
2. Let's find out which Volume Group contains the Logical Volume that holds /dev/mapper/TCPDumpVolGRP-TCPDumpLV
   
   

   [root@Linux01 ~]# lvdisplay /dev/TCPDumpVolGRP/TCPDumpLV --- Logical volume --- LV Name /dev/TCPDumpVolGRP/TCPDumpLV VG Name TCPDumpVolGRP LV UUID hYQs4t-YtY7-51hl-c4ps-4N6d-2W7h-IidcxF LV Write Access read/write LV Status available # open 1 LV Size 3.12 GB Current LE 100 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:5

   Note: You can see the volume group for this file system is TCPDumpVolGRP
   
   
3. Let's find out if the volume group TCPDumpVolGRP has available free space to allocate to the logical volume
   
   

   [root@Linux01 ~]# vgdisplay TCPDumpVolGRP --- Volume group --- VG Name TCPDumpVolGRP System ID Format lvm2 Metadata Areas 3 Metadata Sequence No 5 VG Access read/write VG Status resizable MAX LV 0 Cur LV 2 Open LV 2 Max PV 0 Cur PV 3 Act PV 3 VG Size 11.91 GB PE Size 32.00 MB Total PE 381 Alloc PE / Size 228 / 7.12 GB Free PE / Size 153 / 4.78 GB VG UUID 9fWFIS-vDlg-xOW6-Xmb8-Tkrg-GPZw-ZnUZwh

   Note: This volume group has plenty of free space.  If we were out of physical extents, we would have to add additional physical volumes to this volume group before continuing on.
   
   
4. We will now resize the logical volume TCPDumpLV by adding 3GB
   
   

   [root@Linux01 TCPDumpLV]# lvresize -L +3GB /dev/TCPDumpVolGRP/TCPDumpLV Extending logical volume TCPDumpLV to 6.12 GB Logical volume TCPDumpLV successfully resized [root@Linux01 TCPDumpLV]#

   
   
5. Confirm the new size of the logical volume
   
   

   [root@Linux01 ~]# lvdisplay /dev/TCPDumpVolGRP/TCPDumpLV --- Logical volume --- LV Name /dev/TCPDumpVolGRP/TCPDumpLV VG Name TCPDumpVolGRP LV UUID hYQs4t-YtY7-51hl-c4ps-4N6d-2W7h-IidcxF LV Write Access read/write LV Status available # open 1 LV Size 6.12 GB Current LE 196 Segments 2 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:5

   
   

   [root@Linux01 ~]# pwd /TCPDumpLV [root@Linux01 TCPDumpLV]# df -kh . Filesystem Size Used Avail Use% Mounted on /dev/mapper/TCPDumpVolGRP-TCPDumpLV 3.1G 2.9G 69M 98% /TCPDumpLV

   Note: You will notice that although we have increased the size of the logical volume, the size of the file system has been unaffected.

6. We now need to resize the ext3 file system to utilize the remaining available space within the logical volume
   
   

   [root@Linux01 TCPDumpLV]# resize2fs -p /dev/mapper/TCPDumpVolGRP-TCPDumpLV resize2fs 1.39 (29-May-2006) Filesystem at /dev/mapper/TCPDumpVolGRP-TCPDumpLV is mounted on /TCPDumpLV; on-line resizing required Performing an on-line resize of /dev/mapper/TCPDumpVolGRP-TCPDumpLV to 1605632 (4k) blocks. The filesystem on /dev/mapper/TCPDumpVolGRP-TCPDumpLV is now 1605632 blocks long. [root@Linux01 TCPDumpLV]# df -kh . Filesystem Size Used Avail Use% Mounted on /dev/mapper/TCPDumpVolGRP-TCPDumpLV 6.1G 2.9G 2.9G 50% /TCPDumpLV

Nice work, you just resized your file system while it was online!  Now lets take a look at reducing the size of a file system.

Shrink File System

Decreasing the size of a file system managed with LVM must be done off-line (unmounted.)  To shrink the file system and LV:

• Unmount the file system
• Run a file system check to ensure the integrity of the volume
• Shrink the file system
• Shrink the logical volume

Note: You cannot shrink the file system beyond the amount of free space that is available on it.  So if the file system you want to shrink has 1GB of free space, you will only be able to shrink the volume by 1GB.  However, logical volumes are not as forgiving.  If you are not careful, you can shrink the LV to a size less than what is required by the file system.  If the LV is resized smaller than what the file system has been resized to, things will go very badly for you.  Did we mention you should backup your data before hand?

Let's get started!

1. First, check to see how much space is available
   
   

   [root@Linux01 ~]# pwd /TCPDumpLV [root@Linux01 TCPDumpLV]# df -kh . Filesystem Size Used Avail Use% Mounted on /dev/mapper/TCPDumpVolGRP-TCPDumpLV 6.1G 922M 4.9G 16% /TCPDumpLV

   Note: The disk free command shows that we are using 922MB and have 4.9G available on our file system.  Therefore, we can safely shrink the volume to 1.5G (leaving a little bit for overhead) without any issue.
   
   
2. Unmount the file system
   
   

   [root@Linux01 TCPDumpLV]# cd / [root@Linux01 /]# umount /TCPDumpLV

   
   
3. Check the file system for errors
   
   

   [root@Linux01 /]# e2fsck -f /dev/mapper/TCPDumpVolGRP-TCPDumpLV e2fsck 1.39 (29-May-2006) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information /dev/mapper/TCPDumpVolGRP-TCPDumpLV: 13/802816 files (7.7% non-contiguous), 261017/1605632 blocks [root@Linux01 /]#

   
   
4. Shrink the file system to 1.5GB
   
   

   [root@Linux01 /]# resize2fs /dev/mapper/TCPDumpVolGRP-TCPDumpLV 1500M resize2fs 1.39 (29-May-2006) Resizing the filesystem on /dev/mapper/TCPDumpVolGRP-TCPDumpLV to 384000 (4k) blocks. The filesystem on /dev/mapper/TCPDumpVolGRP-TCPDumpLV is now 384000 blocks long. [root@Linux01 /]#

   
   
5. Shrink the logical file system to 1.5GB
   
   

   [root@Linux01 /]# lvresize -L 1.5G /dev/TCPDumpVolGRP/TCPDumpLV WARNING: Reducing active logical volume to 1.50 GB THIS MAY DESTROY YOUR DATA (filesystem etc.) Do you really want to reduce TCPDumpLV? [y/n]: y Reducing logical volume TCPDumpLV to 1.50 GB Logical volume TCPDumpLV successfully resized [root@Linux01 /]#

   Note: Special precaution should be taken with this step.  It's possible to reduce the logical volume size by more than the size of the file system.  If you do reduce the LV size by more than what you resized the file system to (from step #4), this will almost certainly end very badly for you.  Ensure the LV is large enough for the file system and that you make a backup before hand!
   
   
6. Verify the new size of the logical volume
   
   

   [root@Linux01 ~]# lvdisplay /dev/TCPDumpVolGRP/TCPDumpLV --- Logical volume --- LV Name /dev/TCPDumpVolGRP/TCPDumpLV VG Name TCPDumpVolGRP LV UUID hYQs4t-YtY7-51hl-c4ps-4N6d-2W7h-IidcxF LV Write Access read/write LV Status available # open 0 LV Size 1.50 GB Current LE 48 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:5

   
   
7. Remount the file system and verify the new size
   
   

   [root@Linux01 /]# mount /dev/TCPDumpVolGRP/TCPDumpLV [root@Linux01 /]# cd /TCPDumpLV/ [root@Linux01 TCPDumpLV]# df -kh . Filesystem Size Used Avail Use% Mounted on /dev/mapper/TCPDumpVolGRP-TCPDumpLV 1.5G 920M 497M 65% /TCPDumpLV

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papi |28/11/2009 10:49:12 nice Reply | Quote

jay |07/12/2009 00:57:36 great write up. Would also like to know if there's a way to grow the LV to the maximum available without counting it manually and leaving slack. Reply | Quote

thirt |14/12/2009 03:20:22 Jay - You could do something like: Quote: lvresize -l +100%FREE That should use up all the remaining free space available in the volume group. Hope that helps, Tom Reply | Quote

Jean  - resize dynamic disk |14/07/2010 04:33:07 you can expand the dynamic volume. visit the web page to get more information.--http://www.dynamic-disk.com/resource/resize-dynamic-disk-partition-volume.html Reply | Quote

Slippery |21/01/2010 08:35:30 Many thanks indeed for helping out a Windows guru but Linux amateur. Steve Reply | Quote

nicobo |06/02/2010 11:20:52 Thanks for this 'quickstart' tutorial. I have two remarks : 1. I've found better to use 'lvresize -l' for growing the volume because 'lvresize -L' rounds the given size and therefore does not always end up in what you're expecting 2. In your example I find it a bit confusing to use a size in MB to resize the partition and then a (the same) size in GB to resize the volume. It probably worked for you but I'm not sure it will for everybody (?). Reply | Quote

lazymathstudent |18/05/2010 10:07:44 just look at how much space vgdisplay reports in "Free PE / Size". The correct size is A = PE*4MB, which gives lvresize -L +A /dev/mapper/cpool-bla Reply | Quote

Alex |18/10/2010 15:16:45 Thanks for this article it helped me a lot. Reply | Quote

Nare |24/11/2010 10:08:01 Thnx for this tutorial Reply | Quote

Bravo |21/01/2011 07:37:01 Wow, what a great and straight forward step by step guide My gratitude for the writer Reply | Quote

MXA |21/01/2011 08:55:55 step by step, great howto Thank you Reply | Quote

FooBar  - 1000MB vs 1024MB |06/04/2011 11:07:39 In steps 4 & 5, it looks like you reduce the file system more than you reduce the size of the logical volume. The file system is 1500MB vs 1536 MB (1.5GB) for the volume. Was this intentional to prevent resizing the volume too small? Or do either resize2fs or lvresize use mebibytes instead of megabytes? Thanks. Reply | Quote

Anonymous |29/04/2011 04:27:39 Great stuff buddy!! Reply | Quote

BK  - GREAT JOB! |02/06/2011 18:43:24 Thanks to your LVM refresher course in one URL, I was able to remember how LVM functionality actually works, and wrote some documentation for our staff. It's rough, but I felt I should give back given the excellent documentation you've written. EXPANDING LOGICAL VOLUMES ON A LINUX VM INSTANCE First, down the server you want to add space to. From the VM Console, add more virtual disk with more space than you need. You do NOT want to do this many times, as Logical Volumes (LVM2) have limits. Bring the VM Instance back online, and login as root. Next, we need to join the virtual disk free space to the virtual disk itself. #fdisk /dev/sda (dev/sda is “pseudo-physical” disk drive for the VM instance) M (to print whole list of options.) P (to print out the existing partitions) N (to create new partition, then choose a partition type “p” in this case.) Choose a partition # - one that is not in use, say 3 or 4. Let the system choose start points, and to end of disk. P (print it again, and see what you have created.) L (to label the partition) W (Write it to the disk) Q (Quit. You’ve made space, now to join it to the Volume Group.) Connect to the website below. This is where the real work begins. Read through this section once, noting where the PINK/RED highlights are. They provide the information to use in the next instructional steps! (Your work above fixes problems in Item #3, when vgdisplay does not have free PE.) http://www.tcpdump.com/kb/os/linux/lvm-resizing-guide/all-pages.html Useful command: lvresize -l +100%FREE /dev/mapper/VolGroup00-LogVol00 Instead of just “resizing” by adding 3GB (in the instructions) this one says to use all free space in the volume group for this partition. This is a “last step” instruction to make the change. I highly recommend to reboot and confirm your new partition sizes actually worked. Reply | Quote

Askar  - Nice work |23/06/2011 06:44:09 For for the nice work, using these small ariticles i'm learning about LVM Reply | Quote

Jake Tors |13/07/2011 07:56:53 just wondering where you came up with df -kh. You are asking to display in both kilobytes and human readable format at the same time. just use df -h my friend, df -h. same result. Reply | Quote

Gene Rye  - Trying to umount the drive |20/07/2011 10:26:59 When I try to umount the drive to resize the partion smaller, I get a device busy message. root ~ puts me in my /root directory. When I df -kh the system, I get /dev/mapper/VolGroup00-LogVol00. Folloiwng Step 2, I cd /, and then umount /dev/VolGroup00/LogVol00. Get message device busy. What should I do? thanks Reply | Quote

Gene Rye  - More Info |20/07/2011 10:43:57 I was trying to do this through the desktop. Should this be done through the command line interface? Reply | Quote

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