SPICE: Improved UX On CentOS 5 KVM Guest

As you probably know, KVM is a great way to run virtual machines on a Linux host.  It may not be as refined as VMware Workstation, but it's very close.  And it's open source.

Not all of guest VM's need to provide a graphical desktop like Gnome.   But when they do, SPICE is one of the protocols you can use to access it.  Like RDP, PCoIP, and VNC, SPICE is a remote desktop access protocol.  I use the term "access" instead of "display" because all of these protocols provide more than just a display output channel.  They also provide input channels for serial devices such as keyboards and mice.

Electrical engineers: don't confuse the SPICE protocol with the SPICE circuit emulator.

When the guest is configured correctly, the serial channels provide seamless mouse traversal from the host to the guest, and allows cut-paste between the two.  Without these channels, you can't paste text into the guest from the host and you have to use keyboard escape sequences to release the mouse from the guest.

In short, it's fairly annoying if you have a need to switch quickly between the two environments.

When running newer Fedora, CentOS, and Red Hat guests on a newer host, SPICE input channels just work.  But if you need to run CentOS/RHEL 5.x, it doesn't.  Not "out of the box", anyway.  So here's how.

I'm working with CentOS 5.9.  After installing the base OS on the guest, follow these steps.

1. Install the Feodra EPEL repo configuration.  (Note that the domain name may be different than what you see here.)
   
   rpm -i http://mirror.nexcess.net/epel/5/i386/epel-release-5-4.noarch.rpm
2. Install the SPICE vdagent.
   
   yum install -y spice-vdagent
   
   
3. Verify that the vdagent is enabled to start at boot time.
   
   chkconfig --list|grep spice
   

My host is running Fedora 17.  If you're using virt-manager to access your desktops, then you don't really need the SPICE client (it's built in to virt-manager).  But if you just want to connect with the 'spicec' command, then yum install spice-client. 

If you're accessing the desktop from the network, you need to make sure that SPICE is configured to listen on the right network interface.  By default, it only listens on 127.0.0.1.  In a production environment, your choice will depend on security requirements.  In a lab environment, I usually set this to 0.0.0.0 so I can get to the desktop from anywhere.

Things should start working at this point.  When I first got everything configured, it didn't.  I'm not sure what fixed it (logout?  screen save?) but it's OK now.  The mouse cursor is a little clunky compared to the experience on newer guests, but cut/paste is OK and I don't have to use a magic key combo to release the mouse.

Making ISO Files and Burning CD's

Need to create an ISO image of some directory contents and burn it to a CD or DVD? Here's how I do it on Fedora/RHEL/CentOS.

In (overly) simplistic script form, the making of an ISO9660 image goes like this.

#!/bin/bash
contents="path/to/files"
isodir="path/to/empty/dir"
isoimage="my-image.iso"

mkdir $isodir
cp -a $contents $isodir

mkisofs -R -J -T \
    -V "VOLUME_ID" \
    -A "Description of the contents" \
    -publisher "The Company, Inc" \
    -p "Another Company, Inc" \
    -o $isoimage $isodir

The Rock Ridge protocol (-R) and Joliet fileystem (-J) options specify extensions to the ISO9660 standard that help with OS compatibility. Rock Ridge adds POSIX file capabilites for Unix-compatible systems, and Joliet improves Windows compatibility.

The -T option adds a translation table to each directory, which further enhances compatibility on both Windows and Linux systems.

The remaining options are fairly obvious.  The volume ID (-V) can be up to 32 characters.  You might want to avoid whitespace for easier use on Unix systems, but it's not a requirement.

The other strings for application ID (-A), publisher, preparer (-p), are descriptive strings that can be up to 128 characters.

If you don't specify an output file or device (-o), the output will be written to stdout.

If you choose to write to a file, you can use cdrecord (a symlink to wodim on newer versions of Linux) to burn a CD.  You'll need to know the name of the device file for the optical writer on your system.  It's usually /dev/cdrom, /dev/dvdwriter, or something similar.

The command I use to burn CD's and DVD's is

cdrecord dev=/dev/cdrom my-image.iso.