Shrink guest on hosted platform
Zero out unused space in a Linux VM
Before we try to shrink the virtual disk files, we should try to remove any unneeded files from the virtual machine to free space.
Clean up your repositories:
For example, on Debian-based VMs, you can run
apt-get clean all
to clear out the local repository of retrieved package files.
On red hat based VMs that would be:
yum clean
Next, reboot your VM from a live CD and mount the file systems.
The reason we are doing this from a live CD is that we are going to write out zero's to the file system and we do not want any application - for example a database system like mySQL or postgreSQL - to run out of disk space while we are zeroing out the file system. If mySQL would try to write when your disk is full you risk a corrupted database. So this "reboot from a live CD" step is important!
from your live CD, check out the filesystem of your VM, for example:
fdisk -l
will show you:
cat /dev/zero > zero.fill;sync;sleep 1;sync;rm -f zero.fill
to fill the unused space with zeros.
If you do not have a Live CD, then you can run the command to zero out the unused space as root, but remember to shut down services like databases first.
Zero out unused space on a Windows VM
To do the same with a windows VM, you can use Microsoft's tool sdelete.
Run it as
sdelete -z c:
To clean out the free space on disk c:
Careful!
As of sdelete v1.6 -c and -z have changed meanings, many instructions say -c zeros free space, this is no longer the case, it zeros the space then fills with random data in accordance with DOD spec: DOD 5220.22-M, the trigger to zero space with 0x00 has changed to -z!
Shrink the disk
Then power down the VM and open a terminal on the Linux host.
Navigate to the directory where the .vmdk files are located, e.g.:
cd /var/lib/vmware/Virtual\ Machines/Ubuntu\ Desktop/
You can shrink the .vmdk file as follows:
vmware-vdiskmanager -r Ubuntu\ Desktop.vmdk
On Windows the command also uses the -r option, so I leave that for you as an exercise.
Note that vmware-vdiskmanager is probably not in your search path, so you might have to prepend the vmware-vdiskmanager command with the actual path with the command is located.
