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--- computing:virtmanagerhell [2022/08/08 20:13] – oemb1905
+++ computing:virtmanagerhell [2023/01/15 17:47] (current) – oemb1905
@@ Line 7: / Line 7: @@
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-This is all very old fyi and not current or helpful; might delete it soon. Resize an .img with virt-manager, for example, expanding a 64GB disk to a 124GB disk.  Start by installing the optional tools for this:
+To make a VM from the command line, do the following. Note that this recipe assumes you have already created your virtual switch, br0. It also presumes you have already created your virtual disk, and if you have not, simply run ''sudo qemu-img create -f raw new.img 1000G''.
+  sudo virt-install --name=new.img \
+  --os-type=Linux \
+  --os-variant=debian10 \
+  --vcpu=1 \
+  --ram=2048 \
+  --disk path=/mnt/vms/students/new.img \
+  --graphics spice \
+  --location=/mnt/vms/isos/debian-11.4.0-amd64-netinst.iso \
+  --network bridge:br0
+To clone an existing image, do the following:
+  virt-clone \
+  --original=clean \
+  --name=sequoia \
+  --file=/mnt/vms/students/sequoia.img
+If you have a legacy image that needs to be larger, then install a few tools and the proceed to expand the virtual hard disk as follows:
+  apt install qemu-img kpartx
+  qemu-img resize debian10.img +50G
+After expanding the virtual hard disk, open gparted in X passthrough / command line and expand the existing partition into as much of the the new space as you prefer. And to rename a VM (domain), do the following:
+  virsh shutdown <old-name>
+  virsh domrename <old-name> <new-name>
+To delete a domain, virt-manager uses the undefine command. To remove the accompanying storage with it, parse the command as follows:
+  virsh undefine guest1 --remove-all-storage
+If you need to force stop a machine, virt-manager uses the destroy command, as follows:
+  virsh destroy guest1
+I prefer the raw format (.img) but if I change my mind later, perhaps because I want snapshots, then I can easily shutdown the machine and convert the image as follows. If I change my mind, I can also go in reverse back to raw.
+  qemu-img convert -p -f raw -O qcow2 guest1.img guest1.qcow2
+  qemu-img convert -p -f qcow2 -O raw guest1.qcow2 guest1.raw
+If you do end up using this, then you will need to edit the virtual machine's xml file. To do that, open the file and edit the disk type. Change ''type'' and ''source file='' to match the new type and extension. If you also moved the location, you can edit that now as well.
+  virsh edit guest1
+  <driver name='qemu' type='raw' cache='none'/>
+  <source file='/mnt/vms/students/guest1.qcow2'/>
+Another essential tool is the ability to create snapshots and, when necessary, revert to them. Here are the commands to create snapshot1 and then later revert to that specific snapshot.
+  virsh snapshot-create-as guest1 snapshot1 --description "first snapshot 11-13-22"
+  virsh snapshot-revert guest1 snapshot1
+If you don't care about naming the snapshot or customizing the description, you may optionally create the snapshot by excuting this:
+  virsh snapshot-create guest1
+To create an external snapshot, append the following arguments:
+  virsh snapshot-create-as guest1 snapshot1 --description "first snapshot 11-13-22" --diskspec vda,snapshot=external
+If you want to revert to the latest snapshot, then execute this:
+  virsh snapshot-revert guest1 --current
+If you need to delete a particular snapshot, or delete all children of a snapshot, execute:
+  virsh snapshot-delete guest1 snapshot1
+  virsh snapshot-delete guest1 --current --children-only
+To list all snapshots for a particular guestOS, execute this:
+  virsh snapshot-list guest1
+To get information about the snapshot, these commands help:
+  virsh snapshot-info guest1 snapshot
+  virsh snapshot-dumpxml guest1 snapshot1
+If you need to make a live backup, do the following (Note: make sure that ''sudo apt install qemu-guest-agent'' is installed on the guest OS):
+  virsh domfsfreeze guest1.qcow2
+  qemu-img create -f qcow2 -b guest1.qcow2 snapshot.qcow2
+  virsh domfsthaw guest1.qcow2
+At times you may need to resize or gather information about a particular virtual disk. If they are in the qcow2 format, gather information as follows:
+  qemu-img info disk.qcow2
+To regain space that is being used needlessly, you can sparsify the qcow2 disk. Note that you must install virt-sparsify separately with ''sudo apt install libguestfs-tools''.
+  virt-sparsify --in-place disk.qcow2
+Most importantly, there's often a need to expand a qcow2 disk. For that, I first recommend you backup the disk. Then, you can either specify the desired or target size, or you specify an increment of space to add on to the disk.
+  cp -ar --sparse=always disk.qcow2 disk.bk.qcow2
+  qemu-img resize disk.qcow2 1000G
+  qemu-img resize disk.qcow2 +10G
+Okay, so another big issue with qcow2 images is them growing over time from writes/deletes and then those blocks taking up space on the hypervisor while not actually being used on the guestOS any longer. To stop this, enable unmap on the virtIO disk in virsh, and then schedule a timer within the guest OS to trim those underlying blocks.
+  sudo systemctl enable fstrim.timer
+  sudo systemctl start fstrim.timer
+You can also manually run fstrim and then power down the qcow2 image and convert it. You may optionally use compression to save more space, but it takes very long.
+  fstrim -v /
+  qemu-img convert -O qcow2 guest.qcow2 guest-trimmed.qcow2
+  qemu-img convert -O qcow2 -c guest.qcow2 guest-trimmed.qcow2
+To test trimming functionality, I use a combination of ``ncdu`` which shows actually consumed space on the host OS, along with the following dd command to easily consume and delete space:
+  dd if=/dev/urandom of=file bs=4M count=500
+To create a backup volume inside a guest you create the volume, attach it, and then shell into the guest and format, mount, and create an fstab entry. First, on the hostOS:
+  cd /mnt/vms/backups/vm1-backup-dir/
+  qemu-img create -f qcow2 vm1-backup.qcow2 32G
+  virsh attach-disk guestOS.qcow2 \
+    --source /mnt/vms/backups/vm1-backup-dir/vm1-backup \
+    --target vdb \
+    --persistent
+Then, on the guestOS:
+  mkdir /mnt/backup
+  mkfs.ext4 /dev/vdb
+  mount -t auto /dev/vdb /mnt/backup
+  nano /etc/fstab
+  /dev/vdb /mnt/backup ext4 defaults, 0 0
+The rest from here on out is my attempt at resizing an .img virtual disk using tools exclusively from virsh / virt-manager. These are highly risky moves and totally not needed for day to day operations. It was more of a mission I was on and based on a tutorial I used nearly 15 years ago when expanding a Windows VM I used for teaching software that was only on that VM. At any rate, I have only succeeded twice doing this, and often get confused looking at the l00ps. Proceed with caution!
   sudo apt install libguestfs-tools
@@ Line 86: / Line 220: @@
   kpartx -d debian10.img
-After messing around with this, and succeeding 1 time in resizing the drive this way, I decided that just issuing ''apt install qemu-img kpartx'' and then expanding within the VM's gparted GUI was far easier. It does require moving and/or deprecating swap (or other earlier partitions) or you cannot merge the file system.
- --- //[[jonathan@haacksnetworking.org|oemb1905]] 2022/08/08 00:37//
+ --- //[[jonathan@haacksnetworking.org|oemb1905]] 2023/01/15 10:31//

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