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1612 discussions

Storage and backup considerations
by Thomas Rønshof 27 Sep '11

27 Sep '11

Hi, Some very newbie questions. I have to move an old SCO-Unix server to a Cent OS 6.0 guest on a Cent OS 6.0 Host. The space used on the SCO is 65 GB. How shall i plan the storage ? Make an image based guest of 100 GB an install on that ? Or is LVM based better regarding performance ? Should i allocate 100GB or 200 GB ? What is best ? What about backup ? Should i take backup from the guest with tar/cpio or backup of the image file on the host ? What is the preferable ? Regards Thomas.

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Packet loss between Xen machines
by Aaron Linnen 26 Sep '11

26 Sep '11

We are experiencing some packet loss between xen machines which we haven't seen before. Is this a problem anyone's run into before and/or has ideas on how to diagnose the issue? The setup is CentOS 5 xen-3.0.3-80.el5_3.3 Aaron

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Connection does not support host device enumeration
by Kaushal Shriyan 22 Sep '11

22 Sep '11

Hi, I have "20:04.0 Network controller: Sangoma Technologies Corp. A104d QUAD T1/E1 AFT card" on Host OS, Its not visible on guest OS using linux KVM application. I did open the window for guest from virt-manager on my Ubuntu Linux Desktop 11.04, shut down the guest, then select the "Details" view from the menu on that window, and click "Add Hardware" at the bottom, select "PCI Host Device" in the selections on the left, and find your device in the list of host devices on the right. Then click "Finish". Finally, start your guest up again, and the device should appear. I get "Connection does not support host device enumeration" Any clue ? libvirt-0.8.2-22.el5 version running on CentOS Linux Server version 5.6 Please let me know if you need any additional information Regards, Kaushal

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Linux KVM on CentOS 5.6
by Kaushal Shriyan 21 Sep '11

21 Sep '11

Hi, I have IBM x3650M3 Server with 2 Physical CPU each with quad core configs and 32GB of physical RAM and 600 GB usable space. I am using linux kvm for this purpose. Please correct or suggest me if i am doing wrong I have installed CentOS 5.6 on physical server as host OS. I need to create 2 Virtual Machines with similar configs. virt-install --connect qemu:///system -n vm1 -r 15000 --cpuset=auto -f /var/tmp/vm1.qcow2 -s 200 -c /var/lib/libvirt/images/CentOS-5.6-x86_64-bin-DVD-1of2.iso --vnc --noautoconsole --os-type linux --os-variant generic26 --accelerate --network=bridge:br0 --hvm virt-install --connect qemu:///system -n vm2 -r 15000 --cpuset=auto -f /var/tmp/vm2.qcow2 -s 200 -c /var/lib/libvirt/images/CentOS-5.6-x86_64-bin-DVD-1of2.iso --vnc --noautoconsole --os-type linux --os-variant generic26 --accelerate --network=bridge:br0 --hvm Please let me know the recommended method if there are any changes need to be done in the above command line. I would be eventually running asterisk PBX application on these 2 VM's and also let me know if 2 GB of physical RAM is sufficient for Host OS. Regards, Kaushal

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KVM CO 5.6 VM guest crashes running iSCSI
by Momonth 20 Sep '11

20 Sep '11

Hi All, I'm running KVM host on CentOS 5.6 x64, all of my guests are CO 5.6 x64 as well. I create / run VMs via libvirt. Here are the packages I have: # rpm -qa | egrep "kvm|virt" kvm-83-224.el5.centos python-virtinst-0.400.3-11.el5 kvm-qemu-img-83-224.el5.centos kmod-kvm-83-224.el5.centos libvirt-python-0.8.2-15.el5 etherboot-zroms-kvm-5.4.4-13.el5.centos libvirt-0.8.2-15.el5 libvirt-devel-0.8.2-15.el5 The problem: I attached an iSCSI LUN (netapp appliance) to a guest and everything work fine with iscsi-initiator-utils-6.2.0.872-6.el5: LUN discovery, attaching to the host etc. After that I'm trying to copy ~ 140Gb of data to that LUN via scp from another server in the network and the VM crashes after ~ 1 hour of copying .. Nothing in the VM / KVM host logs importunately. Who has / had similar issues with iSCSI LUNs being connected to a guest? Thanks, Vladimir

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Network traffic control/shaping of guest interfaces
by Emmanuel Noobadmin 20 Sep '11

20 Sep '11

I've been using tc/htb for network control previously to control bandwidth available to different services running on their own IPs on a unvirtualized host. Now, I have put them into their own guest VM. I would like to be able to do something similar to ensure the more crucial service gets more bandwidth as well as ensuring ssh always get reserved bandwidth. However, when I try the good old tc/htb commands on the host, it fails to do anything useful. My script that works on the non-virtualized setup was this TCADD="tc class add dev eth0 parent" $TCADD 1:0 classid 1:1 htb rate 1250kbps ceil 1250kbps $TCADD 1:1 classid 1:10 htb rate 25kbps ceil 150kbps prio 0 $TCADD 1:1 classid 1:11 htb rate 100kbps ceil 300kbps prio 1 $TCADD 1:1 classid 1:12 htb rate 300kbps ceil 600kbps prio 1 $TCADD 1:1 classid 1:19 htb rate 75kbps ceil 150kbps prio 2 TFADD="tc filter add dev eth0 protocol ip parent" $TFADD 1:0 prio 0 u32 match ip dport 10022 0xffff flowid 1:10 $TFADD 1:0 prio 1 u32 match ip dst <public ip ipaddress 1> flowid 1:11 $TFADD 1:0 prio 1 u32 match ip dst <public ip address 2> flowid 1:12 I can't put the restrictions within the guest because I don't want the individual VM admins to be able to stop the script from running. On my new host, I have bridged networking with br0, eth0 and guests running off vnet<n>. I've tried applying tc on br0, eth0, vnet<n> but they don't seem to have any effect based on a 20MB FTP test. I've been googling for a while to find an solution but haven't hit on anything apart from using yet another firewall/router sitting between everything and the Internet. Is there any other solution apart from that?

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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?

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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

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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

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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.

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