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Prevent the firewall from being compromised through libvirtd
by Thomas Luening 27 Jan '20

27 Jan '20

Hello @ all The libvirt-daemon compromises the packet-filtering-rules at daemon-startup, before any VM is started. To prevent this, I first have create a hook-script which deletes existing rules, but apparently these rules are set after the hook. Removing the defined networks was no solution either. Worst of all is, a service restart of the daemon may even completely neutralize the firewall. Is there a solution to prevent this undesirable behavior? No matter how or who what do or with what network configuration a VM is started, the daemon must not compromise the firewall, by altering them. The Firewall is untouchable and taboo. What can I do to disable that? Thank you! Best Regards Tom $ dpkg -l libvirt-daemon ||/ Name Version Architektur Beschreibung +++-=========================-============-============-================================== ii libvirt-daemon 5.0.0-4 amd64 Virtualization daemon $ lsb_release -a Distributor ID: Debian Description: Debian GNU/Linux 10 (buster) Release: 10 Codename: buster

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Repetitive RBD disk definitions
by wferi＠niif.hu 24 Jan '20

24 Jan '20

Hi, I'm using libvirt 5.0.0 on a Ceph cluster. The VM disks are all from the same Ceph pool, so all my <disk> elements are basically the same: <disk type="network" device="disk"> <driver name="qemu" type="raw" cache="none"/> <source protocol="rbd" name="vmdisks/VOLNAME"> <host name="x.y.z.1" port="6789"/> <host name="x.y.z.2" port="6789"/> <host name="x.y.z.3" port="6789"/> </source> <auth username="libvirt"> <secret type="ceph" usage="libvirt_key"/> </auth> <target dev="vdX"/> </disk> ... apart from the VOLNAME and vdX words. Is there a way to factor out (at least part of) the common stuff? This repetition isn't totally unmanageable, just not pretty. Creating a libvirt storage pool seemed like a good solution at first, but I couldn't find a way to "instantiate" volumes in the domain XML (and defining them cluster-wide would mean duplicating what Ceph does, which I'd rather avoid). -- I'd be grateful for any ideas, Feri.

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virsh vol-download uses a lot of memory
by R. Diez 23 Jan '20

23 Jan '20

Hi all: I am using the libvirt version that comes with Ubuntu 18.04.3 LTS. I have written a script that backs up my virtual machines every night. I want to limit the amount of memory that this backup operation consumes, mainly to prevent page cache thrashing. I have described the Linux page cache thrashing issue in detail here: http://rdiez.shoutwiki.com/wiki/Today%27s_Operating_Systems_are_still_incre… The VM virtual disk weighs 140 GB at the moment. I thought 500 MiB of RAM should be more than enough to back it up, so I added the following options to the systemd service file associated to the systemd timer I am using: MemoryLimit=500M However, the OOM is killing "virsh vol-download": Jan 21 23:40:00 GS-CEL-L kernel: [55535.913525] [ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name Jan 21 23:40:00 GS-CEL-L kernel: [55535.913527] [ 13232] 1000 13232 5030 786 77824 103 0 BackupWindows10 Jan 21 23:40:00 GS-CEL-L kernel: [55535.913528] [ 13267] 1000 13267 5063 567 73728 132 0 BackupWindows10 Jan 21 23:40:00 GS-CEL-L kernel: [55535.913529] [ 13421] 1000 13421 5063 458 73728 132 0 BackupWindows10 Jan 21 23:40:00 GS-CEL-L kernel: [55535.913530] [ 13428] 1000 13428 712847 124686 5586944 523997 0 virsh Jan 21 23:40:00 GS-CEL-L kernel: [55535.913532] oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),cpuset=/,mems_allowed=0,oom_memcg=/system.slice/VmBackup.service,task_memcg=/system.slice/VmBackup.service,task=virsh,pid=13428,uid=1000 Jan 21 23:40:00 GS-CEL-L kernel: [55535.913538] Memory cgroup out of memory: Killed process 13428 (virsh) total-vm:2851388kB, anon-rss:486180kB, file-rss:12564kB, shmem-rss:0kB I wonder why "virsh vol-download" needs so much RAM. It does not get killed straight away, it takes a few minutes to get killed. It starts using a VMSIZE of around 295 MiB, which is not really frugal for a file download operation, but then it grows and grows. Note that the virtual machine is not running (shut off) while doing the backup. Last time I tried with an increased memory limit of 5G, "virsh vol-download" was killed when using 7,4 G, and the partially-downloaded volume file weighted 60G. Therefore, it looks like "virsh vol-download" is using a percentage of the downloaded size in RAM. Is there a way to make "virsh vol-download" use less memory? Thanks in advance, rdiez

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How to detect completion of a paused VM migration on the destination?
by Milan Zamazal 22 Jan '20

22 Jan '20

Hi, when a normally running VM is migrated, libvirt sends VIR_DOMAIN_EVENT_RESUMED_MIGRATED event on the destination once the migration completes. I can see that when a paused VM is migrated, libvirt sends VIR_DOMAIN_EVENT_SUSPENDED_PAUSED instead. Since there seems to be nothing migration specific about VIR_DOMAIN_EVENT_SUSPENDED_PAUSED event, my question is: Is it safe to assume on the destination that this event signals completion of the incoming migration (unless VIR_DOMAIN_EVENT_RESUMED_MIGRATED is received before)? Thanks, Milan

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Testing mail delivery
by dberrange＠yahoo.com 22 Jan '20

22 Jan '20

We continue to have problems with mail delivery, especially to Yahoo addresses. This mail is a test to investigate delivery behaviour, please ignore this mail thread. Daniel

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[libvirt-users] Connecting a VM to an existing OVS bridge
by Amir Sela 20 Jan '20

20 Jan '20

Hi, I have an existing OVS bridge, that I can see in ovs-vsctl and use for other purposes. I've edited the machine's XML as instructed in http://docs.openvswitch.org/en/latest/howto/libvirt/ When I try to start the VM, i get error: Cannot get interface MTU on 'ovsbr': No such device Any ideas? (Note: I can't see the ovs switch in brctl show or any other regular kernel tool, should it appear there?) Versions: openvswitch-2.10.1-3.fc30.x86_64 libvirt-daemon-5.1.0-9.fc30.x86_64 Thanks!

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USB-hotplugging fails with "failed to load cgroup BPF prog: Operation not permitted" on cgroups v2
by Pol Van Aubel 20 Jan '20

20 Jan '20

Hi all, I've disabled cgroups v1 on my system with the kernel boot option "systemd.unified_cgroup_hierarchy=1". Since doing so, USB hotplugging fails to work, seemingly due to a permissions problem with BPF. Please note that the technique I'm going to describe worked just fine for hotplugging USB devices to running domains until this change. Attaching / detaching USB devices when the domain is down still works as expected. I get the same error when attaching a device in virt-manager, as I do when running the following command: sudo virsh attach-device wenger /dev/stdin --persistent <<END <hostdev mode='subsystem' type='usb' managed='yes'> <source startupPolicy='optional'> <vendor id='0x046d' /> <product id='0xc215' /> </source> </hostdev> END This returns error: Failed to attach device from /dev/stdin error: failed to load cgroup BPF prog: Operation not permitted virt-manager returns basically the same error, but for completeness' sake, here it is: failed to load cgroup BPF prog: Operation not permitted Traceback (most recent call last): File "/usr/share/virt-manager/virtManager/addhardware.py", line 1327, in _add_device self.vm.attach_device(dev) File "/usr/share/virt-manager/virtManager/object/domain.py", line 920, in attach_device self._backend.attachDevice(devxml) File "/usr/lib/python3.8/site-packages/libvirt.py", line 590, in attachDevice if ret == -1: raise libvirtError ('virDomainAttachDevice() failed', dom=self) libvirt.libvirtError: failed to load cgroup BPF prog: Operation not permitted Now, libvirtd is running as root, so I don't understand why any operation on BPF programs is not permitted. I've dug into libvirt's code a bit to see what is throwing this error and it boils down to <https://github.com/libvirt/libvirt/blob/7d608469621a3fda72dff2a89308e68cc9f…> and <https://github.com/libvirt/libvirt/blob/02bf7cc68bfc76242f02d23e73cad36618f…> but I have no clue what that syscall is doing, so that's where my debugging capability basically ends. Maybe this is something as simple as setting the right ACL somewhere. I haven't touched /etc/libvirt/qemu.conf except for setting nvram. There *is* something about cgroup_device_acl there but afaict that's for cgroups v1, when there was still a device cgroup controller. Any help would be greatly appreciated. Domain log files: Upon execution of the above commands, nothing gets added to the domain log in /var/log/qemu/wenger.log, so I've decided they're likely irrelevant to the issue. Please ask for any additional info required. System information: Arch Linux, (normal) kernel 5.4.11 libvirt 5.10.0 qemu 4.2.0, using KVM. Host system is x86_64 on an intel 5820k. Guest system is probably irrelevant, but is Windows 10 on the same. Possibly relevant kernel build options: $ zgrep BPF /proc/config.gz [22:55:52]: zgrep BPF /proc/config.gz CONFIG_CGROUP_BPF=y CONFIG_BPF=y CONFIG_BPF_SYSCALL=y CONFIG_BPF_JIT_ALWAYS_ON=y CONFIG_IPV6_SEG6_BPF=y CONFIG_NETFILTER_XT_MATCH_BPF=m # CONFIG_BPFILTER is not set CONFIG_NET_CLS_BPF=m CONFIG_NET_ACT_BPF=m CONFIG_BPF_JIT=y CONFIG_BPF_STREAM_PARSER=y CONFIG_LWTUNNEL_BPF=y CONFIG_HAVE_EBPF_JIT=y CONFIG_BPF_EVENTS=y # CONFIG_BPF_KPROBE_OVERRIDE is not set # CONFIG_TEST_BPF is not set Regards, Pol Van Aubel

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Prevent virsh live migration from copy zero -- increment copy on live migration possible ?
by Oliver Dzombic 18 Jan '20

18 Jan '20

Hi, i am doing a live migration like this: [root@nodeA ~]#virsh migrate --copy-storage-all --verbose --live kvm1776 qemu+ssh://nodeb/system which works fine with libvirt version 6. The zfs backed hdd is 100G, while its thin-provisioned. The real data on it is 1G. So even its 1G of data, virsh copies a lot of zero's as it seems. There is a lot of HDD IO and network activity, but in fact the size at the target volume does not grow ( since there are no more data ). After it successfully finished the copy, i tried what will happen with the --copy-storage-inc parameter: [root@nodeB ~]# virsh migrate --copy-storage-inc --verbose --live kvm1776 qemu+ssh://nodea/system But that didnt change anything. Even both volumes are identical now, again the whole copy of all ( non existing ) 100GB. Is there any way to make libvirt just copy real data and not Zero's that actually do not exist and causing network and HDD IO traffic ? Thank you ! -- Mit freundlichen Gruessen / Best regards Oliver Dzombic Layer7 Networks mailto:info@layer7.net Anschrift: Layer7 Networks GmbH Zum Sonnenberg 1-3 63571 Gelnhausen HRB 96293 beim Amtsgericht Hanau Geschäftsführung: Oliver Dzombic UST ID: DE259845632

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Bridge-less VM
by Rob Roschewsk 17 Jan '20

17 Jan '20

I'm trying to create a free standing VM that doesn't connect to a bridge. This is supposedly do able according to the WIKI: https://libvirt.org/formatdomain.html#elementsNICSEthernet But with a config similar to: <interface type='ethernet'> <target dev='mytap1' managed='no'/> <model type='virtio'/> </interface> When starting the domain I get the error: error: internal error: process exited while connecting to monitor: 2020-01-16T18:08:04.788860Z qemu-system-x86_64: -netdev tap,id=hostnet0,vhost=on,vhostfd=26: could not open /dev/net/tun: Operation not permitted Checked permissions on /dev/net/tunand it's 666 If I just configure it as a "bridge" connection the domain starts. Then I can use brctl to remove it from the bridge to get what I want. That just proves it possible but with extra steps (Shout out to Rick and Morty) Thoughts?? Running Ubuntu 16.04.1 Kernel 4.15.0-74 libvirt 1.3.1-1ubuntu10.27 qemu 1:2.5+dfsg-5ubuntu10.41 Thanks, --> Rob

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Volume file permissions and huge volume downloads
by R. Diez 17 Jan '20

17 Jan '20

Hi all: I am using the libvirt version that comes with Ubuntu 18.04.3 LTS. I want to backup a virtual machine in a foolproof way: - Gracefully shutdown the VM. - Backup the disk image. - Restart the VM. I wrote the following script to do that: https://github.com/rdiez/Tools/blob/master/VirtualMachineManager/BackupVm.sh Writing that script was difficult enough because of the virsh limitations (in my opinion) described in the comments. But at least it works. The main problem is that libvirt sets the ownership and permissions of volume files in such a way that a standard user cannot access them, even if it is member of the 'libvirt' group. While the VM is running, volume file permissions are like this: -rw-r----- 1 libvirt-qemu kvm [...] /var/lib/libvirt/images/YourVmDisk.qcow2 When the VM is shutoff: -rw-r----- 1 root root [...] /var/lib/libvirt/images/YourVmDisk.qcow2 The trouble is, I want to access that .qcow2 file when the VM is shutoff. I would really like not to run my script as root. I could not find a way to specify the permissions for the .qcow2 files, so I tried editing the group ownership for the whole pool: virsh pool-edit default <target> <path>/var/lib/libvirt/images</path> <permissions> <mode>0711</mode> <owner>0</owner> <group>131</group> </permissions> </target> Setting <group> to "libvirt" did not work (XML validation error), so I tried the numeric ID of that group (131). That did not work. When I restart libvirt with "service libvirtd restart", my changes to the pool XML file disappear (!). Later on, I found out that you can download a volume like this: virsh vol-download --pool default YourVmDisk.qcow2 YourVmDisk.qcow2 The trouble is that I created the virtual disk with a maximum size of 120 GB. I copied it around a few times, so I think it has lost any "sparseness" inside. Command "virsh vol-download" takes ages and downloads all those 120 GB. My script uses "qemu-img convert", which discards all unused space and writes just 17 GB of data, and that is without turning compression on. The whole backup takes seconds instead of minutes. Can somebody help me with these issues? Thanks in advance, rdiez

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