How can I compact the VHD file with Ubuntu?

Question

I use windows server 2008r2 with role Hyper-V. The guest system is Ubuntu 12.04 LTC. It is situated on the dynamic virtual hard disk.

I want to compact this VHD (The real size is 50 GB, 360 GB on the disk). But I can not do this, because the Ubuntu file system is not NTFS. What do I need (gparted, sdelete, ...) for solving this problem?

The main problem is that the filesystem is not NTFS, but ext4.

The answer:

1) Download systemrescuecd

http://sourceforge.net/projects/systemrescuecd/files/sysresccd-x86/3.8.1/systemrescuecd-x86-3.8.1.iso/download

2) Add this .iso to the quest OS Ubuntu

3) Start this virtual machine

4) Use zerofree

zerofree /dev/sda1

5) Poweroff this virtual machine

6) Use Hyper-V manager (Edit -> defragmentation)

This vhd was 360 Gb. Now 70 GB.

If you want to answer your own question, please post an *answer*, not an edit to the question itself. — Massimo, Jun 18 '16 at 00:31
consider `fstrim` in 2019, especially for ext4 under LVM https://superuser.com/questions/1491437/how-to-properly-compact-hyper-v-dynamic-sized-vhdx-files-for-linux-vms — Alec Istomin, Dec 01 '19 at 01:04

score 6 · Accepted Answer · answered Nov 08 '13 at 10:15

6

Poweroff your VM, backup the VHD, and run another virtual machine (I use SystemRescueCD since it's small and fast) that has the ext4 partition available to it, i.e., a HD for SysRescue (but don't mount it!). From the SysRescue VM, run 'zerofree' on the ext4 partition, poweroff that VM, and then use your Administration Website to compact the VHD.

answered Nov 08 '13 at 10:15

rickhg12hs

394
2
9

I begin do it (download SystemRescueCD, then zerofree /dev/sda1), but I do not know can I compact this VHD in Windows (after all free space will be null) – AmShegar Nov 12 '13 at 12:15
1

Try the [Hyper-V Manager](http://virtuatopia.com/index.php/Creating_and_Configuring_Hyper-V_Virtual_Hard_Disks_(VHDs)#Modifying_Existing_Hyper-V_Virtual_Hard_Disks). – rickhg12hs Nov 12 '13 at 18:55

score 5 · Answer 2 · edited Jul 14 '21 at 00:56

I can confirm: zerofree is working to compact virtual disk files

BUT: you don't need to use any rescue CDs or to mount the VHDX in another virtual machine:

sudo apt-get install zerofree

Boot into recovery mode, then run:

zerofree /dev/sda1

After that, we have to start the optimization for the virtual disk file. On the server hosting the VHDX file, create the following file ShrinkVhdx.ps1:

[CmdletBinding()]
Param(
    $VHDFiles
)

# Find the disks
foreach($VHD in $VHDFiles){
    Write-Verbose "Working on $VHD, please wait"
    Write-Verbose "Current size $([math]::truncate($(Get-VHD -Path $VHD).FileSize/ 1GB)) GB"
    
    Mount-VHD -Path $VHD -NoDriveLetter -ReadOnly
    Optimize-VHD -Path $VHD -Mode Full

    Write-Verbose "Optimize size $([math]::truncate($(Get-VHD -Path $VHD).FileSize/ 1GB)) GB"
    Dismount-VHD -Path $VHD
    
    Write-Verbose ""
}

And now run the file and enjoy the released disk space :-)

ShrinkVhdx.ps1 .\hdd1.vhdx

This depends on the filesystem if it's XFS you are out of luck using zerofree. — Brad, Jun 18 '16 at 00:31

score 2 · Answer 3 · answered Nov 08 '13 at 08:23

2

The process appears to be

Backup your current VHD file.
Use Snapshot manager to delete/merge any snapshots.
Zero fill the unused disk space

viz

sudo apt-get install secure-delete 
sudo sfill -llz .

This creates a file called oooooooo.ooo filled with 0s. You should repeat the sfill command on all partitions I guess.

Note this isn't quick either, it will take hours if not days to complete.

Compact
Profit

answered Nov 08 '13 at 08:23

user9517

114,104
20
206
289

thanks, but I do not have the internet on the machine with hyper-v and vhd with linux. So I can not do "sudo apt-get install secure-delete" – AmShegar Nov 12 '13 at 12:17

score 1 · Answer 4 · answered Nov 21 '13 at 13:08

1

1) Download systemrescuecd

http://sourceforge.net/projects/systemrescuecd/files/sysresccd-x86/3.8.1/systemrescuecd-x86-3.8.1.iso/download

2) Add this .iso to the quest OS Ubuntu

3) Start this virtual machine

4) Use zerofree

zerofree /dev/sda1

5) Poweroff this virtual machine

6) Use Hyper-V manager (Edit -> defragmentation)

answered Nov 21 '13 at 13:08

AmShegar

259
1
2
9

2

Hyper-V manager does not have a (Edit -> defragmentation) – Brad May 25 '16 at 21:58

score 0 · Answer 5 · edited Apr 13 '17 at 12:14

I did try to start Systemrescuecd in a 2nd gen machine. But it didn't work, so I created a new 1st gen machine and added the VHDX to it. systemrescuecd started. I didn't do any operations. Removed the 1st gen machine and put the VHDX back in the original machine. Then Ubuntu didn't start up at all. Only Grub-menu.

See my post here: Hyper-V Ubuntu vhdx scsi ide

So be aware of this, and do take backup (I didn't this time)...

score 0 · Answer 6 · answered Jun 18 '16 at 00:28

You can do this by checking some parameters in the following files: /sys/block//queue/discard_granularity /sys/block//queue/discard_max_bytes if either have a 0 it's probably not supported by your hardware + software configuration.

Here's a full tutorial on doing this at: http://www.1337admin.org/uncategorized/compacting-virtual-disks-on-generation-2-linux-hyper-v-2012-r2-vms/

How can I compact the VHD file with Ubuntu?

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