virt September 2011

virt@lists.centos.org

23 participants
18 discussions

Getting guest to detect new drive without reboot
by Emmanuel Noobadmin 20 Sep '11

20 Sep '11

I've got a CentOS 5.6 guest running on 6.0 host. Using virsh attach-disk, I attached a new raw file as vdc However, the guest does not detect this new disk. In the past, I've used the following echo "0 0 0" > /sys/class/scsi_host/host#/scan command to make a CentOS system scan for new drives. However in the guest, there is no host in scsi_host so this isn't an option. I can't seem to find any information on doing this any other way apart from a reboot. Does anybody know if there is any other way?

2 2

Having trouble starting more than 8 Xen guests
by Scot P. Floess 19 Sep '11

19 Sep '11

All, I've spent quite a few hours trying to figure this out to no avail... I have two machines and the result is the same on both. Additionally, each machine does not support full hardware virtualization... I am able to create 8 VMs. When attempting to create ninth VM, I get the following error: Error: Device 51712 (vbd) could not be connected. /etc/xen/scripts/block failed; error detected. To create the VMs, I use the command: "xm create [vm name]" My machine has 8 GB RAM and is an "old school" dual opteron box. "uname -a" is: Linux centos-host-2 2.6.18-274.3.1.el5.centos.plusxen #1 SMP Wed Sep 7 06:25:54 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux To be clear, I can shutdown any one of the 8 VMs and then run the ninth "xm create" - that VM will start... I did some google'ing and from what I cn tell that error arises due to the lack of loop back devices (there being 8 by default)... I've tried both using MAKEDEV (in my /etc/rc.local) to create a number of loop back devices and put max_loops in my grub,.conf file. For example here is what I have in grub.conf now: title CentOS (2.6.18-274.3.1.el5.centos.plusxen) root (hd0,0) kernel /xen.gz-2.6.18-274.3.1.el5.centos.plus module /vmlinuz-2.6.18-274.3.1.el5.centos.plusxen ro root=LABEL=/ max_loop=64 module /initrd-2.6.18-274.3.1.el5.centos.plusxen.img Due to wrapping, max_loop is actually on the module /vmlinuz- line... I also tried to put max_loop on the kernel line as well... As I mentioned above, I also created the loop back devices from /etc/rc.local like so: /sbin/MAKEDEV -d /dev -m 64 loop And, once I can log in to the machine, I do see everything in /dev (for example /dev/loop0 to /dev/loop64) Has anyone else had this problem? If so, how did you resolve it???? Thanks ahead of time!!!!! Scot P. Floess RHCT (Certificate Number 605010084735240) Chief Architect FlossWare http://sourceforge.net/projects/flossware http://flossware.sourceforge.net https://github.com/organizations/FlossWare

2 3

Slightly OT: Centos KVM Host/Guest functions and LVM considerations
by Jeff Boyce 16 Sep '11

16 Sep '11

Greetings - I will be getting a new server for my company in the next few months and am trying to get a better understanding of some of the basic theoretical approaches to using Centos KVM on a server. I have found plenty of things to read that discuss how to install KVM on the host and how to install a guest and setup the network bridge, and all the other rudimentary tasks. But all of these how to's make the assumption that I have a philosophical understanding of how KVM is incorporated into the design of how I use my server, or network of virtual servers as the case may be. So in general I am looking for some opinions or guidance from KVM experts or system administrators to help direct me along my path. Pointers to other HowTo's or Blogs are appreciated, but I have run out of Google search terms over the last month and haven't really found enough information to address my specific concerns. I suspect my post might get a little long, so before I give more details of my objectives and specific questions, please let me know if there is a better forum for me to post my question(s). The basic questions I am trying to understand are, (1) what functions in my network should my host be responsible for, (2) what functions should logically be separated to different VMs, and (3) how should I organize disks, raid, LVM, partitions, etc to make best use of how my system will function? Know I know these questions are wide open without any context to what the purpose(s) of my new server are, and my existing background and knowledge, so that is the next part. I am an ecologist by education, but I manage all the computer systems for my company with a dozen staff. I installed my current Linux server about 7 years ago (RHEL3) as primarily a Samba file server. Since then the functions of this server have expanded to include VPN access for staff and FTP access for staff and clients. Along the way I have gained knowledge and implement various other functions that are primarily associated with managing the system, such as tape backups, UPS shutdown configuration, Dell's OMSA hardware monitoring, and network time keeping. I am certainly not a Linux expert and my philosophy is to learn as I go, and document it so that I don't have to relearn it again. My current server is a Dell (PE2600) with 1 GB RAM and 6 drives in a RAID 5 configuration, without LVM. I have been blessed with a very stable system with only a few minor hiccups in 7 years. My new server will be a Dell (T610) with 12 GB RAM, 4 drives in a RAID 5 configuration, and an iDRAC6 Enterprise Card. The primary function of my new server hardware will be as the Samba file server for the company. It may also provide all, or a subset of, the functions my existing server provides. I am considering adding a new gateway box (ClearOS) to my network and could possibly move some functions (FTP, VPN, etc.) to it if appropriate. There are also some new functions that my server will probably be responsible for in the near future (domain controller, groupware, open calendar, client backup system [BackupPC]). I am specifically planning on setting up at least one guest VM as a space to test and setup configurations for new functions for the server before making them available to all the staff. So to narrow down my first two questions how should these functions be organized between the host system and any guest VMs? Should the host be responsible just for hardware maintenance and monitoring (OMSA, APC shutdown), or should it include the primary function of the hardware (Samba file server)? Should remote access type functions (FTP & VPN) be segregated off the host and onto a guest? Or should these be put on the gateway box? I have never worked with LVM yet, and I am trying to understand how I should setup my storage space and allocate it to the host and any guests. I want to use LVM, because I see the many benefits it brings for flexible management of storage space. For my testing guest VM I would probably use an image file, but if the Samba file server function is in a guest VM I think I would rather have that as a raw LV partition (I think?). The more I read the more confused I get about understanding the hierarchy of the storage (disks.RAID.[PV,VG,LV].Partition.Image File) and how I should be looking at organizing and managing the file system for my functions. With this I don't even understand it enough to ask a more specific question. Thanks to anyone that has had the patients for reading this much. More thanks to anyone that provides a constructive response. Jeff Boyce Meridian Environmental

5 7

Re: [CentOS-virt] P2V of NEtware 3.12 working server to Centos >=5.x
by Ed Heron 07 Sep '11

07 Sep '11

On Thu, 2011-09-08 at 02:35 +0530, Rajagopal Swaminathan wrote: > > I would suggest setting up a CentOS server with Samba and convert the > > DOS network stack, if you can. Samba appears to be much more > > supportable, currently. Take a look at the FreeDOS project, too, as an > > example of getting DOS to work in a more recent environment. The > > biggest concern (after getting the clients to talk to Samba) is that > > there have been a few choices made in Samba with respect to file > > sharing/locking mechanisms. With old software, you may have to look at > > those settings. > > I am not sure about freedos as there is a Piece of custom built ISA > hardware and the forget about replacing it. there is a budget(was > there any?) constraint at clients end. Just suggesting looking at the docs for ideas. > > I google'd netware virtual machine and saw a few > > links to virtualizing Netware 3 under VMWare which might give you some > > insights. > > No additional cash flow for software :p ..... :) Just another suggested reading for ideas. > > > > Either way, do it in a separate test environment to work out any > > issues prior to production deployment. > > > > Even buying is a hard disk is a constraint. (Cash outflow constraint, > remember :) ) If you can't buy hardware, then you already have a Linux box running KVM? > > If I hadn't been strongly encouraged (successfully) to de-clutter my > > software repository, I'd pull out my old Netware 3.12 disks and try > > installing on a virtual machine. > > > > If only I had that luxury of having those original _working_ floppy disks. > If I had to virtualize an existing machine, I'd boot the equipment with a Linux Live CD and copy (using dd/ssh) the raw disk data to a virtual disk on the virtual machine server. Verify the copy is accurate with md5sum. Then, make another copy to start a virtual machine with. I'd still suggest your best option would be to take one of the DOS clients and get it to connect to a Samba server and migrate the data.

1 0

CentOS-6 KVM virt-manager will not shutdown guest
by James B. Byrne 07 Sep '11

07 Sep '11

I have a CentOS-6 guest VM configured on a CentOS-6 host. If I run virt-manager then I can start the guest VM but once it is running I cannot get a shutdown command to have effect. To shutdown the running guest I either must select Force Off from the Shut Down menu or open the guest console and issue shutdown from the command line. Is there some setting that is required to have Shut Down have effect when issued from within virt-manager? is this a bug or a configuration problem? When I issue the shutdown command to the guest then there is no entry made in /var/log/messages. It just has no effect. However, if I issue a reboot command from the same menu then I get an error: libvirtd: 16:43:51.027: error: VirLibConnError 450 : this function is not supported by the connection driver: virDominReboot Am I to infer that Reboot and Shutdown options actually are not available to use from the virt-manager Shut Down menu, notwithstanding that they are present? -- *** E-Mail is NOT a SECURE channel *** James B. Byrne mailto:ByrneJB@Harte-Lyne.ca Harte & Lyne Limited http://www.harte-lyne.ca 9 Brockley Drive vox: +1 905 561 1241 Hamilton, Ontario fax: +1 905 561 0757 Canada L8E 3C3

2 1

P2V of NEtware 3.12 working server to Centos >=5.x
by Rajagopal Swaminathan 07 Sep '11

07 Sep '11

Greetings, I would be grateful if anybody can kindly give a pointer to port a Working netware 3.12 server using Centos >=5.x KVM howto? -- Regards, Rajagopal

2 3

Network configuration on KVMs
by James B. Byrne 02 Sep '11

02 Sep '11

In the Redhat EL6 virtualization guide ( http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualiz… ) I read this: # Configure iptables Configure iptables to allow all traffic to be forwarded across the bridge. # iptables -I FORWARD -m physdev --physdev-is-bridged -j ACCEPT # service iptables save # service iptables restart Disable iptables on bridges Alternatively, prevent bridged traffic from being processed by iptables rules. In /etc/sysctl.conf append the following lines: net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0 Reload the kernel parameters configured with sysctl. # sysctl -p /etc/sysctl.conf However, later in the same guide ( http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualiz… ) I read this: * Enabling IP forwarding (net.ipv4.ip_forward = 1) is also required for shared bridges and the default bridge. Note that installing libvirt enables this variable so it will be enabled when the virtualization packages are installed unless it was manually disabled. Note Note that enabling IP forwarding is not required for physical bridge devices. When a guest is connected through a physical bridge, traffic only operates at a level that does not require IP configuration such as IP forwarding. Which leaves me a little confused. Is this talking about some form of network device other than the installed NIC? How is this information integrated with the requirement given in section 10.3? Can someone explain to me how these two sections relate to one another? A second difficulty I encounter is that the first vm guest that I created does not seem to have any interface configuration file for etho in /etc/sysconfig/network-scripts. In fact, I see no ifcfg-x files at all. Am I supposed to create these by hand or have I somehow missed a configuration step in virt-manager? -- *** E-Mail is NOT a SECURE channel *** James B. Byrne mailto:ByrneJB@Harte-Lyne.ca Harte & Lyne Limited http://www.harte-lyne.ca 9 Brockley Drive vox: +1 905 561 1241 Hamilton, Ontario fax: +1 905 561 0757 Canada L8E 3C3

1 0

cloudstack - http://cloudstack.org
by Ian B 01 Sep '11

01 Sep '11

Citrix have open sourced their recently acquired cloud management platform 'Cloudstack'. It apparently supports multiple hypervisors: Xen, KVM, Vmware ESXi The install guide is worth a read even if you're not considering installing it as it goes over some 'best practice' config for storage, networking setup etc. http://download.cloud.com/releases/2.2.0/CloudStack2.2.9InstallGuide.pdf Just wondering if anyone has any experience with it? - Ian

2 1

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

virt September 2011