[clug] Seeking FOSS Hypervisor and Management GUI

George at Clug Clug at goproject.info
Tue Sep 30 20:37:16 MDT 2014

    From the discussion so far, I may stay with KVM, Virt-Manager (not
sure if it would be a good idea (could cause stability issues) for me
to manually install later versions of virt-manager and required

The virtualisation features that I want are a short list, just
snapshots are an important item on the list, so Virt-Manager supports
most of what I want to do, and with a few command line commands, my
needs could be answered.  More experimentation and more experience
will help me learn the limitations and reliability of Linux

And not sure when Debian or CentOS are likely to update to
Virt-Manager > 1.0 and thus support snapshots from GUI. So as
suggested, learning the command line for virsh may be the way to go. 

I find command lines difficult, slower to learn, I can never remember
the syntax, and I am prone to type the wrong thing, whereas using a
GUI, you can look for the feature you want to use, and then select
it.  For me, I find the GUI method of managing systems is much faster
and less prone to user error.  Keeping  scripts of commands for
specific tasks (for working on your servers), and running these
scripts when needed, is one way to minimize user typing errors. Maybe
I can write a script for each virtual machine that "takes snapshot,
installs update, validates services are still available,
removes/consolidates snapshot, or automatically roles back, and then
emails me the result" ? and then schedule this script for 2:00am each
day or week or month depending on the frequency I want updates to be

If anyone else out there is using virtualisation, I would be
interested in reading about your adventures.  Bob, Stephen if you
have any other personal experiences you are willing to share, it will
make fun reading too.

_Here is bit more of my (continuing) research;_

Live snapshots A feature called external snapshotting allows one to
take a live snapshot of a virtual machine without turning it off.
Currently it only works with qcow2 and raw file based images.

Snaphots are supported using the qcow2 format; the disk image file
contains both the disk snapshots and the CPU/RAM state. 

VM snapshots can be managed using the following commands.
$ virsh snapshot-create 
$ virsh snapshot-list “VM-Name”
$ virsh snapshot-revert  
$ virsh snapshot-delete “VM-Name” 1234567890


This table contains virsh command options for snapshots: 
Table 15.7. Snapshot options
Command     Description 
snapshot-create  Create a snapshot.  
snapshot-current  Get the current snapshot.  
snapshot-delete  Delete a domain snapshot.  
snapshot-dumpxml  Dump XML for a domain snapshot.  
snapshot-list  List snapshots for a domain.  
snapshot-revert  Revert a domain to a snapshot.  


_Other sites_

yum install tigervnc-server 

_There are several different types of snapshots possible_. Some idea
on that:

Internal snapshot: A type of snapshot, where a single QCOW2 file will
hold both the ‘saved state’ and the ‘delta’ since that saved
point. ‘Internal snapshots’ are very handy because it’s only a
single file where all the snapshot info. is captured, and easy to
copy/move around the machines.

External snapshot: Here, the ‘original qcow2 file’ will be in a
‘read-only’ saved state, and the new qcow2 file(which will be
generated once snapshot is created) will be the delta for the changes.
So, all the changes will now be written to this delta file.
‘External Snapshots’ are useful for performing backups. Also,
external snapshot creates a qcow2 file with the original file as its
backing image, and the backing file can be /read/ in parallel with the
running qemu.

VM State: This will save the guest/domain state to a file. So, if you
take a snapshot including VM state, we can then shut off that guest
and use the freed up memory for other purposes on the host or for
other guests. Internally this calls qemu monitor’s ‘savevm’
command. Note that this only takes care of VM state(and not disk

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