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1610 discussions

Xen network problem
by Ken Bass 30 Oct '09

30 Oct '09

I have a machine with 8 CPU's (2 quad xeons). (Centos 5.4 currently). Currently, I am running 2 domUs. One with 4 CPUs and another with 2. 2 remain unused. I am using routed networking. On the one machine with 4 CPU's, there is a cronjob at 4am which utilizes the CPU/disk pretty heavily. It is rebuilds a mailing list archive (using MHonarc) and rebuilds a search engine index (swish-e). I dont think it uses more than 1 CPU though because the index rebuilding is not multi threaded, as far as I know. This cron runs at 4am each day and takes about 7 minutes. My ISP is telling me that their alarms are going off because they cannot ping my server between 4am and 4:07am. It sounds like the domU is impacting the overall Xen performance. Is there anything I can do to tune this? It kinda defeats the whole Xen virtualization concept if a single CPU messes up the network. I am going to try to add a 'nice' to the crontab for the 4am job, but still, something doesn't seem correct. Any suggestions would be much appreciated. Thanks!

3 8

Xen vs. KVM console
by Dennis J. 26 Oct '09

26 Oct '09

Hi, I'm trying to get the console support in KVM working as well as on Xen but right now I'm stuck. I followed these instructions: http://prefetch.net/blog/index.php/2009/06/17/redirecting-the-centos-and-fe… This works out fairly well except that I cannot watch the bootup of the machine in the vnc console anymore only on the serial console and I also don't get any output on the vnc console on shutdown. Is there a way to configure the serial console in such a way that I don't lose a part of the functionality of the vnc console? Regards, Dennis

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Re: [CentOS-virt] Move Windows within an LV to another pv safely
by Christopher G. Stach II 26 Oct '09

26 Oct '09

----- "Ben M." <centos(a)rivint.com> wrote: > What a mess that turned out to be. Hey, maybe it was your "awesome > numbering" <ducking and running>. jk, probably because I forgot to > take > some meds today or something. Measure twice. Cut once. :) > Oh, the dd quit on me before complete. Is it okay making the target lv > bigger than the source when I try it again or does it have to be > exact? > I need some extra disk space in that xen vm too. You can make it larger if you want. The partition table copied from the source will only have the original size allocated. Did you allocate the new LV with the same number of extents on a VG with the same extent size? It should work perfectly, if so. -- Christopher G. Stach II

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Re: [CentOS-virt] Move Windows within an LV to another pv safely
by Christopher G. Stach II 26 Oct '09

26 Oct '09

----- "Ben M." <centos(a)rivint.com> wrote: > Does this appear to be a sound procedure? I have one inline question. I read your version of the procedure and it looks like you want to skip the pvmove. That's fine, but it means more downtime (an unreliable estimate is one minuted per GB). In that case, you don't even need the snapshot. You won't need a point in time copy if you are copying from a stable source. > 1. Shutdown domU source (source lvname = win2k8-source) which is never > file mounted in Xen dom0, just "lvm'd". Yeah, just turning off the guest and making sure it doesn't have the ``o'' flag set in the ``lvs'' output is enough. I hope that nothing else had it open (for writing) while your guest was running. :) > 2. snapshot source win2k8-source to win2k8-snapshot > [How long do I wait before bringing DomU source back up? Is there in > indication when it is done? It is approx. 50gig] A few milliseconds. It will return almost immediately. > 3. Bring up domU (Is this necessary if seeking accurate data state, > would rather keep offline on a weekend dayrather than lose data > entries.) The snapshot won't change. It's not necessary if you don't need your guest to be up. In fact, you can skip the whole snapshot bit if you don't care about downtime for your guest. Just dd from win2k8-source. You can't perform this step if you aren't going to use pvmove. Your source will change and your snapshot will be out of date. You would lose all of your changes between the snapshot and when you reboot the guest the second time. > 4. Create identical lv extent space (win3k8-target) on target pv/vg Yes, but win2k8-target. :) Since you are copying to a new VG, you can just keep the LV name the same. > 5. dd if=/dev/vgsnapshotsource/win2k8-snapshot > of=/dev/vgtarget/win2k8-target Yes, but you can specify a larger block size and it will take less time. I personally just default to using bs=1048576 for most things, even if it's not ideal. > 6. Shutdown DomU, change xen win2k8-source domU conf file phy: > reference to win2k8-target Nope. Keep it the same. You don't want to run from the snapshot or the backup copy, unless you're skipping the pvmove. If you are, you want to change the VG and/or LV name to the non-backup copy. > 6a. Drop snapshot, rename source lv to win2k8-old If you were going with pvmove, you would perform that after this step. > 7. Start "new" domU. > 8. test extensively, if works, run for few a day or two. Keep *-old as > fallback for a week or so. Then move to an archive using dd. So, we have two possible procedures intermingled here. The major differences are Procedure A (lots of downtime) and Procedure B (minimal downtime). Procedure A ~~~~~~~~~~~ 1. Create target LV with geometry identical to source LV geometry 2. Stop guest. 3. dd 4. Modify guest configuration to point to target LV 5. Start guest This is the procedure to use if simplicity is desired. As a perk, your source LV becomes your backup. Procedure B ~~~~~~~~~~~ 1. Create backup LV with geometry identical to source LV geometry 2. Stop guest. 3. Create snapshot of source LV 4. Start guest 5. dd from snapshot of source LV to backup LV 6. Drop snapshot of source LV 7. vgextend source VG with additional PV 7. pvmove source LV to additional PV (opt) 8. vgsplit [source VG into additional VG with additional PV] (opt) 9. Modify guest configuration [to point to source LV on additional VG] Procedure B can be different for Linux guests in that, depending upon your guest filesystem choices (ext3 journal, in particular) and site specific caching issues, step 2 could be "Pause guest" and step 4 would then be "Resume guest". Depending upon how you handle your PVs and VGs in the optional 8 and 9 steps, you may need to shut down your guest(s). Your desire to have one VG per PV will probably necessitate that being done eventually. -- Christopher G. Stach II

2 7

Need info on vnet mapping to guests
by Neil Aggarwal 25 Oct '09

25 Oct '09

Hello: I have a host running two KVM guests. The guests use br0 and each has a static IP address. I am trying to figure out if there is a way to use snmpd on the host to measure the traffic usage of the guests. I do not want to require anything running on the guests since I do not control them. Looking at netstat -in on the host, I see this info: Kernel Interface table Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg br0 1500 0 237609 0 0 0 13615 0 0 0 BMRU eth0 1500 0 967594 0 0 0 354576 0 0 0 BMRU lo 16436 0 63 0 0 0 63 0 0 0 LRU virbr0 1500 0 0 0 0 0 32 0 0 0 BMRU vnet0 1500 0 29802 0 0 0 306940 0 0 0 BMRU vnet1 1500 0 311556 0 0 0 789331 0 0 0 BMRU Looking at the firewall logs for packets that hit the firewall, I see that vnet1 is connected to guestA and vnet0 is connected to guestB. Is there a better way to determine which vnet is connected to which guest? Also, does the mapping change when I stop and start guests or reboot the host? Thanks, Neil -- Neil Aggarwal, (281)846-8957, www.JAMMConsulting.com Will your e-commerce site go offline if you have a DB server failure, fiber cut, flood, fire, or other disaster? If so, ask about our geographically redundant database system.

6 10

Sending function key like F12 to a booting cd
by Torkil Zachariassen 21 Oct '09

21 Oct '09

Under Xen I am booting a virtual server from a recovery CD-Rom (actually a iso image) When the cd boots in the console window I have to send the single key "F12" to the window within 10 seconds from start, otherwise it will try to boot from harddisk. Pressing F12 in the console window does not work - and I tried sdl as well as vnc. I can send various Ctrl+Alt-combinations using the menu item "Send key" but not Fn keys. Does anyone know how to send F12 or other function keys to a booting cd ? ...torkil... on centos 5.3, xen-3.0.3 and virt-manager 0.5.3.

1 0

VNC not connecting
by Neil Aggarwal 21 Oct '09

21 Oct '09

Hello all: I am trying to install CentOS 5.4 as a KVM guest. The host is running CentOS 5.4 and does not have X installed. I used ssh to connect to the host and ran this command (I formatted it for readability, it is all on one line): virt-install -n jamm12e -r 1024 --vcpus=1 --check-cpu --os-type=linux --os-variant=rhel5 --hvm --accelerate --cdrom=/tmp/CentOS-5.4-x86_64-netinstall.iso -f /usr/local/virt/jamm12e.img -s 20 -b br0 --vnc --vncport=5903 When I do that, I get this error: (virt-viewer:3083): Gtk-WARNING **: cannot open display: Domain installation still in progress. You can reconnect to the console to complete the installation process. I did not expect the installation to try connect to the display since I told it to use VNC. Next, I tried to connect TightVNC viewer from my Windows XP laptop. I entered 192.168.2.200:3 as the server and tried to connect, but that failed. Did I miss something in the VNC configuration? I don't see any other parameters to use. Thanks, Neil -- Neil Aggarwal, (281)846-8957, www.JAMMConsulting.com Will your e-commerce site go offline if you have a DB server failure, fiber cut, flood, fire, or other disaster? If so, ask about our geographically redundant database system.

2 2

Error setting up bridge with static IP address
by Neil Aggarwal 20 Oct '09

20 Oct '09

Hello: I am trying to follow the RHEL virtualization guide to set up a bridge on a system running CentOS 5.4. I copied my ifcfg-eth0 to ifcfg-eth0:1 and set its content to this: DEVICE=eth0:1 HWADDR=[The MAC address from eth0] ONBOOT=yes BRIDGE=br1 I then created ifcfg-br1 with this content: DEVICE=br1 TYPE=Bridge BOOTPROTO=static BROADCAST=192.168.2.255 IPADDR=192.168.2.202 NETMASK=255.255.255.0 NETWORK=192.168.2.0 ONBOOT=yes DELAY=0 When I do service network restart, I get this error: error in ifcfg-eth0:1: didn't specify device or ipaddr I specified the device so it looks like it wants an IP address but that is contrary to what I am reading on the Internet. Any ideas what went wrong? Thanks, Neil -- Neil Aggarwal, (281)846-8957, www.JAMMConsulting.com Will your e-commerce site go offline if you have a DB server failure, fiber cut, flood, fire, or other disaster? If so, ask about our geographically redundant database system.

2 4

Re: [CentOS-virt] LVM Lockout
by Christopher G. Stach II 19 Oct '09

19 Oct '09

----- "Ben M." <centos(a)rivint.com> wrote: > They show up in /dev as sd(x)s, but not in /dev/mapper with the > nvidia_ > handle. I type dmraid -ay and there they are, but not auto-magically > like the first pair do at boot. I don't see a conf file to make this > happen You can temporarily edit rc.sysinit around the dmraid logic and add some debugging to see what it's doing or not doing. Have you considered skipping dmraid and just using MD RAID? You would probably be better off. -- Christopher G. Stach II

2 1

Problem with CentOS 5.3 Xen and Windows Server 2008 HVM DomU
by Veli-Pekka Kestilä 19 Oct '09

19 Oct '09

Hi, I have CentOS 5.3 64bit and couple of Windows Server 2008 32Bit DomU's on it. Problem is that I got hit with the "A clock interrupt was not recevied on a secondary processor within the allocated time interval" Blue Screen when trying to run with more than one CPU When searching around I found that official XEN distribution (development version) has some fixes for it, but is there anything I could do on CentOS / windows quest to get the things working with more than one CPU. Greetings, Veli-Pekka Kestilä

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