Open Source

Extending partitions on Linux VMware virtual machines

Lauren Malhoit explains how she extended her Linux partitions.

I  had a couple Zenoss VMware appliances that run Linux that needed to have more space allocated to them.  I knew just adding another hard drive wouldn't solve the issue so I set about finding the least intrusive way to do this and not break the whole VM appliance.  If you've ever used Zenoss, you know the last thing you want to do is re-configure all of your settings again!

There is some information out there on this, but I found most of it to be hard to understand and didn't really explain what the steps were.  If you're someone who isn't used to working with Linux, I imagine it would be almost impossible to change these settings confidently.  So, here are the steps I followed to extend my Linux partitions.  This only applies to ext3 disks that use the logical volume manager.  If you're running a RedHat, CentOS or other similar Linux distro, this process will work for you.

  1. Shutdown the VM
  2. Right click the VM and select Edit Settings
  3. Select the hard disk you would like to extend
  4. On the right side, make the provisioned size as large as you need it
  5. Click OK
  6. Power on the VM
  7. Connect to the command line of the Linux VM via the console or putty session
  8. Log in as root
  9. The fdisk command provides disk partitioning functions and using it with the -l switch lists information about your disk partitions.  At the command prompt type fdisk -l
  10. The response should say something like Disk /dev/sda : xxGB. (See Figure A)
  11. At the command prompt type fdisk /dev/sda. (if dev/sda is what was returned after step 10 as shown in Figure A)
  12. Type p to print the partition table and press Enter (also shown in Figure A)
  13. Type n to add a new partition
  14. Type p again to make it a primary partition
  15. Now you'll be prompted to pick the first cylinder which will most likely come at the end of your last partition (ex: /dev/sda3 ends at 2610).  So I chose 2611 for my first cylinder, which is also listed as the default.
  16. If you want it to take up the rest of the space available (as allocated in step 4), just choose the default value for the last cylinder.
  17. Type w to save these changes
  18. Restart the VM
  19. Log back in as root
  20. At the command prompt type fdisk -l. You'll notice another partition is present.  In Figure B it is listed as sda4.
  21. You need to initialize this new partition as a physical volume so you can manipulate it later using the Logical Volume Manager (LVM).
  22. Now you'll add the physical volume to the existing volume group using the vgextend command. First type df -h to find the name of the volume group.  In Figure C, the name of the volume group is vg_root. Now type vgextend [volume group] /dev/sdaX. (ex: vgextend vg_root /dev/sda4)
  23. To find the amount of free space available on the physical volume type vgdisplay [volume group] | grep "Free"
  24. Extend the logical volume by the amount of free space shown in the previous step by typing lvextend  -L+[freespace]G /dev/volgroup/volume. (ex: lvextend -L+20G /dev/vg_root/lv_root)
  25. You can finally expand the ext3 file system in the logical volume using the command resize2fs /dev/volgroup/volume (ex: resize2fs /dev/vg_root/lv_root).
  26. You can now run the df command to verify that you have more space—df -h

Figure A

Figure B

Figure C

It seems like there are a lot of steps to this process, but it's actually pretty quick and easy if you can afford to restart your server.  So far I haven't had any issues with dynamically extending the partitions and I'm getting a lot less Zenoss notifications about lack of free space.

About Lauren Malhoit

Lauren Malhoit has been in the IT field for over 10 years and has acquired several data center certifications. She's currently a Technology Evangelist for Cisco focusing on ACI and Nexus 9000. She has been writing for a few years for TechRepublic, Te...

Editor's Picks