CentOS - Sep 2011 - Centos 6 First Install, gripes - cool things- tips/help

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.

> Finally got a new server the other day.
> You know I had to try out centos 6 with this one.
Can you give me the specs of your server


---
Michel Donais

On Sep 21, 2011 7:51 PM, "Bob Hoffman" <bob at bobhoffman.com>
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.
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
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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