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1610 discussions

KVM vs ESXi
by Drew 18 May '11

18 May '11

Morning Everyone, I'm busy doing a rebuild of my home server and am tossing between VMware and KVM for this build. I already have experience with ESX, we use it at work, but I'm debating trying out KVM for a while. The server itself is a budget build using a Supermicro X8SAX board w/ i7-950 & 12GB RAM, LSI 3081 SAS RAID (1068e based), rolled into a NorcoTek 16 Bay SAS case. Not fancy but also decent enough for home use. I don't expect high performance out of this unit so unless the gear is hopelessly outclassed, I'm not in a position to entertain upgrading. Right now forking over $1000-$1500 on a $2000 system for a pair of higher end LSI/3ware/Acreca controller just isn't in the budget. ;-) My question to everyone are these: -How well does KVM support Windows Guests? I'm already running a Server 2008r2 and WHS 2011 (based on 08r2) machines at home which I want to consolidate into this box. -Does KVM have a concept of virtual switches and and are they tied to physical NICs? ESXi allows me to create a vSwitch that isn't tied to a physical NIC so I can create a DMZ that exists solely within the host system. I'd like to replicate that if possible. I know these are probably questions that I could answer on my own by RTFM but I have already, and never really got the answers I needed. Pretty much every how-to assumed I'd be doing basic stuff and not dabbling with advanced stuff. I also know that what's written doesn't always match what's in the field and you folks are the field. And with CentOS 6 just around the corner (no flame wars please, my nomex pants are at the cleaners :-P ) I'm wanting to know if it's worth holding off another month or so on finalizing my build. Thanks, -- Drew "Nothing in life is to be feared. It is only to be understood." --Marie Curie

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Discover what vnet is attached to a kvm guest
by carlopmart 13 May '11

13 May '11

Hi all, How can I see what vnet is attached to a certain kvm guest?? For example: I have a kvmguest1. When I launch this guest with virsh command, virsh creates a new vnetX interface for this guest. How can I extract this virtual net interface (vnet0, vnet1, vnet2 or so on) using a script?? Thanks. -- CL Martinez carlopmart {at} gmail {d0t} com

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Xen live migration
by Lars Hecking 12 May '11

12 May '11

I can't get xen live migration to work - CentOS 5.6. I have set up xend-config.sxp as per RHEL5 virtualization guide, but when I try it, I get [root@xenhost1 ]# xm migrate testwww xenhost2 -l Error: (104, 'Connection reset by peer') Usage: xm migrate <Domain> <Host> Migrate a domain to another machine. Options: -h, --help Print this help. -l, --live Use live migration. -p=portnum, --port=portnum Use specified port for migration. -r=MBIT, --resource=MBIT Set level of resource usage for migration. Any ideas what to check? brctl, xend-config.sxp, lsof, are all in agreement with http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/Virtualiz….

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Launch scripts after kvm guest starts and before kvm guest stops
by carlopmart 12 May '11

12 May '11

Hi all, Is it possible to launch scripts after kvm guest starts and before kvm stops with libvirt or another kvm tool?? Thanks. -- CL Martinez carlopmart {at} gmail {d0t} com

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KVM switch in promiscuous mode
by carlopmart 11 May '11

11 May '11

Hi all, I am trying to enable promiscuous mode on a kvm switch due to sniff all traffic using snort installed on a kvm guest. I have found a partial solution configuring this bridge with "brctl setaging br0 0", but all vms sees all traffic. I think the soultion is using ebtables but I didn't found any doc about how can I do under kvm (and upstream recommends disable this function). Any ideas?? Thanks. -- CL Martinez carlopmart {at} gmail {d0t} com

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Re: [CentOS-virt] A question about memory ballooning
by carlopmart 07 May '11

07 May '11

> And the opposite question, can memory balloon be deallocated?? And is > it possible to do this automatically or is an error to do this?? I think your understanding of ballooning may be backwards. The purpose of the balloon driver is to give the host system a way of recovering memory from the guest when the demands on the host's physical memory exceed the amount available. The balloon inflates within the guests forcing them to swap or take other memory management measures. When the pressure on the host eases the balloon deflates automatically. Sorry Drew, but I don't understand the use of balloon driver like you explains. According to RedHat's docs: "The balloon driver allows guests to express to the hypervisor how much memory they require. The balloon driver allows the host to efficiently allocate memory to the guest and allow free memory to be allocated to other guests and processes. Guests using the balloon driver can mark sections of the guest's RAM as not in use (balloon inflation). The hypervisor can free the memory and use the memory for other host processes or other guests on that host. When the guest requires the freed memory again, the hypervisor can reallocate RAM to the guest (balloon deflation). " http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualiz… (The balloon driver) I don't see in this doc any reference to "balloon driver is to give the host system a way of recovering memory from the guest when the demands on the host's physical memory exceed the amount available" -- CL Martinez carlopmart {at} gmail {d0t} com

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Package updates and "required" reboots
by Ben M. 06 May '11

06 May '11

I still operate under the assumption that glibc and kernel updates "require" a reboot to be prudent on a Linux OS. With CentOS Xen 5.6 (standard installation, SELinux enabled) is there an FAQ or general user consensus as to when to do a reboot after what updates?

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Where is my qemu command?
by Jussi Hirvi 27 Apr '11

27 Apr '11

KVM virtualization is full of wonders. :-/ I would need to attach an USB disk to a vm, but how? The command "qemu" would provide a way: [root@a134-224 yum.repos.d]# man qemu-kvm > QEMU(1) > NAME > qemu-doc - QEMU Emulator User Documentation > > SYNOPSIS > usage: qemu [options] [disk_image] (...) > -usbdevice devname > Add the USB device devname. But when I try it: [root@a134-224 yum.repos.d]# qemu start -usbdevice host:059f:1018 mail -bash: qemu: command not found That command syntax is probably ot right yet, but the main question is, where is qemu? I was tempted to yum-install qemu from rpmforge, but I would rather not. Besides the rpmforge version has a conflict with another manual page. - Jussi -- Jussi Hirvi * Green Spot Suvilahdenkatu 1 B 78 * 00500 Helsinki * Finland Tel. +358 9 493 981 * Mobile +358 40 771 2098 (only sms) jussi.hirvi(a)greenspot.fi * http://www.greenspot.fi

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xen/ppp
by Fernando Hallberg 27 Apr '11

27 Apr '11

Hi, I'm installed xen4.0.1 for testing purposes in my home gateway and when booting with xen kernel ppp connection fails. Any idea ? -- Fernando Hallberg fernando(a)flexdigital.com.br http://www.flexdigital.com.br Fone/Fax: +55 45 3222-3222 Cascavel - PR - Brasil

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A question about memory ballooning
by carlopmart 26 Apr '11

26 Apr '11

Hi all, How can I manage automatically memory ballooning under a kvm host (C5.6 and future C6)?? For example if I define a kvm guest to boot up with 512MB of RAM and I have configured 1GB as a maximum memory for this guest, how can I allocate this memory when guest will need it?? And the opposite question, can memory balloon be deallocated?? And is it possible to do this automatically or is an error to do this?? Thanks. -- CL Martinez carlopmart {at} gmail {d0t} com

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