On Sep 21, 2011 7:51 PM, "Bob Hoffman" <bob@xxxxxxxxxxxxxx> wrote:
>
> Finally got a new server the other day.
> You know I had to try out centos 6 with this one.
>
> dual quad cores, 24 gb ram (12 for each cpu) 6 working drives bays.
>
> My first big surprise was the partition system with anaconda. It is a
> lot different than the centos 5.x version.
> I am sure it is a bug that it has options for hot spares but does not
> allow it to be ungreyed out.
> I think in the end I will have to manually go into command line and take
> the third drive of the mirror and turn it into a hot spare.
>
> Second issue, which quite shocked me, was the loss of the ability to
> clone a drive during the install. In 5.x I would make all the raid
> partitions, LVM/groups, boots, etc. on one drive, then simply hit
> 'clone' to make the second (and third spare) in the array.
> This time I had to manually do each and every drive, exactly as the
> other, partition by partition. Not fun if you are reinstalling a lot to
> test configs and to get it right.
>
>
> Virtual Machines sound cool and this will be my first attempt. That
> nasty selinux 'silently' is keeping me from putting the images on the
> second raid 1 array I have...sigh. Initial install of virt machine stuff
> popped me right into the command line, even though red hat specifically
> says the graphic stuff has more options.
> Second install used all the graphic desktop stuff to make sure I had the
> option (first time ever saw linux desktop, sweet).
> Interesting that the initial settings of my host had absolutely no
> network access at all. I had to manually change the network scripts to
> enable them...each time I reinstalled to play around. (host needs access
> for ssh and such).
>
> Surprised to find a large (75%?) of packages relating to virtual
> machines not selected in the packages during install...odd. Some might
> be dependencies, but some obviously were not installed the first few
> times until I caught that.
> qemu not selected during install of virt machine....?
>
> Still working on getting the raids to work right (first time adding a
> second 'non system' raid 1) with the whole 'no hot spare' and 3 drives
> as one. Sure is hard to tell it all apart in the graphic desktop since
> all the drives are named exactly the same.
> Learned to never touch the lvm manager graphically, it just seems to not
> understand the raid setups and wants to reinitialize or destroy
> everything. I'll stick to command line for that.
>
> Best part...using an ipmi card with kvm so I can sit on my windows and
> do pics/vids of the process for a nice detailed website how to...all the
> way from bios to deploy...kvm, web, guests, etc...should be fun...should be.
>
> Luckily for me, Kernel based virtual machine guys decided to use the
> abbreviation KVM instead of KbVM. There are about 10 billion pages on
> kvm switches and tons of other junk, as well as books. Kbvm? Not so
> much. If I could read Danish (or dutch or german?) I could buy the
> single book in existence to help with KbVM. Sigh. Should be an experience.
>
> I will be posting a lot of stuff on a private forum (well, open to
> public, but no registrations) about what worked for a stand alone
> server, hosting multiple websites in a KVM environment... Will even try
> to use SElinux all the way also.
>
> If you want access to post things in that forum, send me an email and I
> will gladly add you.
>
> Nothing more fun than boxes of pizza, coke, and mad google searches when
> a new version of redhat/centos comes out....
>
>
> see ya in the funny papers.
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I ran into a few of those things too. For the networking to work on firstboot you have to enable it in the install, but its not obvious. There is a button on the hostname screen to open NetworkManager. It defaults to dhcp but not to be up on boot.
I have a similar setup for my first KVM server. It's really amazing how well it performs especially compared to my current ESXi server on similar hardware, and with all the power and control of using Linux that you don't get with ESXi. My server is a dual six-core Xeon server with 16GB RAM, and for storage I have a RAID 1 array for the system and 6 drives in RAID 6 for the VM storage, with 6 more bays to use. Your server definitely sounds like a good one to explorer virtualization. My ESXi server with only 16GB of RAM has 10 VMs (8 CentOS), so 24GB could do a many more easily.
For the KVM install I found I had to either check all 4 groups for Virtualization during install or run `yum groupinstall "Virtualization*"` . I prefer the later because I can audit what gets installed. I'd also highly recommend SElinux stay enabled for a KVM server, especially in production. That one host will be the single point of failure or compromise for all the guest VMs. Also SElinix helps ensure the VMs stay independent of one another. To use something other than /var/lib/libvirt/images for the VM images, you need to run the following, where /vmstore is the storage location (change accordingly).
yum install policycoreutils-python
semanage fcontext -a -t virt_image_t "/vmstore(/.*)?"
restorecon -R /vmstore
I have a "getting started" write up specific to KVM on CentOS 6, it may have a few helpful parts though it's a very minimal configuration, http://itscblog.tamu.edu/startup-guide-for-kvm-on-centos-6/ .
If your going to use virt-manager heavily, I'd also look at the bottom of that page for a slightly newer version of virt-manager to use on CentOS 6.
- Trey
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