Wiki - public:trouble

blockdev

Anonymous (anonymous@undisclosed.example.com) — 2016-10-24T06:18:52+00:00

Live migration error Error description Although live migration does work for some vhosts from one kvm host to another, it causes error messages for some other vhosts using the same kvm hosts. The log files deliver hints to an unstoppable block job:

cache

Anonymous (anonymous@undisclosed.example.com) — 2018-01-11T13:21:51+00:00

Invisible LVM device Error description An LVM partition is visible on an iSCSI initiator: root@kvm55:~# lvs LV VG Attr LSize Origin … images vg -wi-ao 200.00g lv_dbslave5501 vg -wi-a- 20.00g lv_dbserver5501 vg3_dbserver -wi-ao 4.98g

checksum

Anonymous (anonymous@undisclosed.example.com) — 2016-12-18T12:37:36+00:00

LVM checksum error Error description The problem can begin with the inaccessibility (ping, VNC console, serial console) of a vhost. The vhost can be shut off (virsh destroy vhost), but the vhost cannot be restarted (virsh start vhost). The command

comm

Anonymous (anonymous@undisclosed.example.com) — 2017-11-12T03:13:30+00:00

No communication with a virtual host Error description The first hint to the error are often monitoring error messages stating that the vhost is down. Trials afterwards to access the vhost via network (e.g. ping) fail. After login to the vhost (e.g. from the serial console) it can be found that no outgoing network communication from the vhost is possible.

dm

Anonymous (anonymous@undisclosed.example.com) — 2017-11-12T03:08:05+00:00

Remaining DM devices Error description LVM devices are often generated and removed by automatic processes. Examples are the creation of vhosts or the generation of snapshots while performing backups. During these processes LVM devices are sometimes removed while belonging DM devices still remain. The error becomes visible when LVM partitions cannot be created. This happens because DM devices of the same name still exist.

iscsi

Anonymous (anonymous@undisclosed.example.com) — 2016-07-10T08:00:15+00:00

iSCSI hard disk errors Error description When using kernel versions of v3.19 and above multipath connection losses and scsi disk errors occur and are reported in log files. Affected virtual hosts can become inaccessible and virtual disks stored on iscsi devices can become corrupted.

libvirtd

Anonymous (anonymous@undisclosed.example.com) — 2017-01-12T10:54:18+00:00

Hanging process 'libvirtd' Error description A running daemon 'libvirtd' is the process through which the command 'virsh' communicates with running vhosts. Sometimes the process becomes inaccessible: root@kvm55:~# ps ax |grep libvirtd 7691 ? Zl 0:00 [libvirtd]

lvm

Anonymous (anonymous@undisclosed.example.com) — 2015-07-12T12:32:02+00:00

Cannot create logical volumes Error description Althouh there is enough free space inside the affected LVM volume group no logical volumes can be created. root@kvm5:~# vgs VG #PV #LV #SN Attr VSize VFree vg3 1 19 0 wz--n- 750.00g 430.00g vg 1 2 0 wz--n- 451.51g 1.51g root@kvm5:~# lvcreate -s -n nas_bkup -L 5G /dev/SCSI/nas Insufficient free space: 1280 extents needed, but only 0 available

mapping

Anonymous (anonymous@undisclosed.example.com) — 2015-07-12T12:27:58+00:00

Faulty mapping between iSCSI and multipath devices Error description In another section the device depenencies for KVM host 'kvm55' were already displayed: root@kvm55:~# dmsetup ls --tree 350002ac21d622071 (252:4) ├─ (8:32) └─ (8:16) vg-images (252:0) └─ (8:4) vg3_nas-lv_nas5501 (252:5) └─350002ac21d632071 (252:2) ├─ (8:64) └─ (8:48) vg3_dbserver-lv_dbserver5501 (252:3) └─ (8:32) vg-lv_dbslave5501 (252:1) └─ (8:4)

multipath

Anonymous (anonymous@undisclosed.example.com) — 2024-06-07T08:17:49+00:00

Unnecessary multipath devices Error description Sometimes local hard disks are also controlled by multipath. The command multipath -l then displays these disks as multipath devices although they only have one path. In the example below is the last displayed device an unnecessary multipath device with only one path:

multipath2

Anonymous (anonymous@undisclosed.example.com) — 2016-02-10T19:47:45+00:00

No multipath devices found Error description As stated here multipath hardly causes trouble. But a case was observed, where the command multipath -l did not display any multipath devices although the host was properly logged into iSCSI LUNs: root@kvm55:~# iscsiadm -m session tcp: [1] 10.48.2.11:3260,582 iqn.2000-05.com.3pardata:25820002ac002071 tcp: [2] 10.48.2.10:3260,482 iqn.2000-05.com.3pardata:24820002ac002071 root@kvm55:~# multipath -l root@kvm55:~#

network

Anonymous (anonymous@undisclosed.example.com) — 2016-12-18T12:36:54+00:00

No network communication via vhost interface Error description Suddenly network communication via the management interface of the KVM host is not possible. The command ifconfig displays an active ethernet interface but no outgoing network packages. The switch port to which the network interface is connected is shown as active. Disconnecting and reconnecting the network cable between switch port and ethernet port does not solve the problem. Firewall restrictions (e.g. by iptables) are not confi…

vmbuilder

Anonymous (anonymous@undisclosed.example.com) — 2016-07-25T15:29:27+00:00

Error while creating vhosts with vmbuilder Error description One opportunity to create a vhost on a KVM host is to use vmbuilder like e.g. so: vmbuilder kvm ubuntu --suite trusty --flavour virtual --arch i386 \ -o --libvirt qemu:///system In order to use vmbuilder the package