今天部署了一套K版的OpenStack環境后，啟動nova-compute后，日志里狂報如下錯誤（因為其內部有定時任務需要去連libvirtd進程）：
2015-08-14 10:01:00.061 28580 TRACE nova.virt.libvirt.host File "/usr/lib64/python2.7/site-packages/libvirt.py", line 105, in openAuth 2015-08-14 10:01:00.061 28580 TRACE nova.virt.libvirt.host if ret is None:raise libvirtError('virConnectOpenAuth() failed') 2015-08-14 10:01:00.061 28580 TRACE nova.virt.libvirt.host libvirtError: no connection driver available for qemu:///system
剛開始看到這個錯誤，首先第一反應是不是 libvirtd 進程沒有啟起來，於是 ps 查看確定下，發現已經啟動起來了：
[root@localhost ~]# ps aux | grep libvirtd root 2648 0.0 0.0 112640 980 pts/1 S+ 10:34 0:00 grep --color=auto libvirtd root 31850 0.1 0.0 1053776 7264 ? Ssl 10:17 0:01 /usr/sbin/libvirtd --listen
后來，嘗試直接執行下 virsh list 命令，同樣得到如下錯誤：
[root@localhost ~]# virsh list error: failed to connect to the hypervisor error: no valid connection error: no connection driver available for <null> error: Failed to reconnect to the hypervisor
然后在想是不是URI不對，於是我指定URI再次嘗試執行命令，同樣返回錯誤：
[root@localhost ~]# virsh -c qemu:///system list error: failed to connect to the hypervisor error: no connection driver available for qemu:///system
為保持每次使用的URI都正確，后來我將 /etc/libvirt/libvirt.conf 配置文件里的 uri_default 直接設置為 qemu:///system：
[root@localhost ~]# cat /etc/libvirt/libvirt.conf # # This can be used to setup URI aliases for frequently # used connection URIs. Aliases may contain only the # characters a-Z, 0-9, _, -. # # Following the '=' may be any valid libvirt connection # URI, including arbitrary parameters #uri_aliases = [ # "hail=qemu+ssh://root@hail.cloud.example.com/system", # "sleet=qemu+ssh://root@sleet.cloud.example.com/system", #] # # This can be used to prevent probing of the hypervisor # driver when no URI is supplied by the application. uri_default = "qemu:///system"
然后重啟 libvirtd 進程，通過 systemctl 命令查看下 libvirtd 進程的狀態，發現有如下3個錯誤：
[root@localhost ~]# systemctl status libvirtd libvirtd.service - Virtualization daemon Loaded: loaded (/usr/lib/systemd/system/libvirtd.service; enabled) Active: active (running) since Fri 2015-08-14 10:11:13 CST; 4s ago Docs: man:libvirtd(8) http://libvirt.org Main PID: 30568 (libvirtd) CGroup: /system.slice/libvirtd.service └─30568 /usr/sbin/libvirtd --listen Aug 14 10:11:13 localhost.localdomain libvirtd[30568]: libvirt version: 1.2.8, package: 16.el7_1.3 (CentOS BuildSystem <http://bugs.centos.org>, 2015-05-12-20:12:58, worker1.bsys.centos.org) Aug 14 10:11:13 localhost.localdomain libvirtd[30568]: failed to load module /usr/lib64/libvirt/connection-driver/libvirt_driver_storage.so /usr/lib64/libvirt/connection-driver/...e reference Aug 14 10:11:13 localhost.localdomain libvirtd[30568]: failed to load module /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so /usr/lib64/libvirt/connection-driver/lib...eFileCreate Aug 14 10:11:13 localhost.localdomain libvirtd[30568]: Module /usr/lib64/libvirt/connection-driver/libvirt_driver_lxc.so not accessible Aug 14 10:11:13 localhost.localdomain systemd[1]: Started Virtualization daemon. Hint: Some lines were ellipsized, use -l to show in full.
從上面錯誤來看，兩個錯誤是由於libvirt_driver_storage.so、libvirt_driver_qemu.so加載失敗，一個錯誤是由於沒有libvirt_driver_lxc.so module。
於是查看下目錄 /usr/lib64/libvirt/connection-driver/ 看看是否都有上面三個module：
[root@localhost ~]# ll /usr/lib64/libvirt/connection-driver/ total 1996 -rwxr-xr-x 1 root root 107440 May 13 04:16 libvirt_driver_interface.so -rwxr-xr-x 1 root root 148600 May 13 04:16 libvirt_driver_network.so -rwxr-xr-x 1 root root 107144 May 13 04:16 libvirt_driver_nodedev.so -rwxr-xr-x 1 root root 165688 May 13 04:16 libvirt_driver_nwfilter.so -rwxr-xr-x 1 root root 1175776 May 13 04:16 libvirt_driver_qemu.so -rwxr-xr-x 1 root root 86448 May 13 04:16 libvirt_driver_secret.so -rwxr-xr-x 1 root root 233448 May 13 04:16 libvirt_driver_storage.so
發現libvirt_driver_storage.so、libvirt_driver_qemu.so存在，而libvirt_driver_lxc.so確實不存在。
對於 libvirt_driver_lxc.so不存在 的情況，應該是相應的rpm包沒有安裝，我們只需要安裝下即可：
[root@localhost ~]# yum install libvirt-daemon-lxc
安裝完后，再次通過 systemctl 查看下 libvirtd 進程的狀態，剩下兩個錯誤還是沒有得到解決：
[root@localhost ~]# systemctl status libvirtd libvirtd.service - Virtualization daemon Loaded: loaded (/usr/lib/systemd/system/libvirtd.service; enabled) Active: active (running) since Fri 2015-08-14 10:14:23 CST; 3s ago Docs: man:libvirtd(8) http://libvirt.org Main PID: 31204 (libvirtd) CGroup: /system.slice/libvirtd.service └─31204 /usr/sbin/libvirtd --listen Aug 14 10:14:22 localhost.localdomain libvirtd[31204]: libvirt version: 1.2.8, package: 16.el7_1.3 (CentOS BuildSystem <http://bugs.centos.org>, 2015-05-12-20:12:58, worker1.bsys.centos.org) Aug 14 10:14:22 localhost.localdomain libvirtd[31204]: failed to load module /usr/lib64/libvirt/connection-driver/libvirt_driver_storage.so /usr/lib64/libvirt/connection-driver/...e reference Aug 14 10:14:23 localhost.localdomain libvirtd[31204]: failed to load module /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so /usr/lib64/libvirt/connection-driver/lib...eFileCreate Aug 14 10:14:23 localhost.localdomain systemd[1]: Started Virtualization daemon. Hint: Some lines were ellipsized, use -l to show in full.
於是查看 /var/log/message 關於libvirtd進程的系統日志，發現錯誤日志：
Aug 14 10:14:22 localhost journal: failed to load module /usr/lib64/libvirt/connection-driver/libvirt_driver_storage.so /usr/lib64/libvirt/connection-driver/libvirt_driver_storage.so: symbol dm_task_get_info_with_deferred_remove, version Base not defined in file libdevmapper.so.1.02 with link time reference
Aug 14 10:14:23 localhost journal: failed to load module /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so: undefined symbol: virStorageFileCreate
從上面錯誤來看，undefined symbol，很明顯，是因為driver所需要的引用未定義，於是想應該是 libdevmapper.so.1.02 庫太老，與 libvirtd 庫不匹配，於是就嘗試更新下 device-mapper：
[root@localhost ~]# yum update device-mapper
更新后，重啟 libvirtd 進程，再次查看其狀態：
[root@localhost ~]# systemctl restart libvirtd [root@localhost ~]# systemctl status libvirtd libvirtd.service - Virtualization daemon Loaded: loaded (/usr/lib/systemd/system/libvirtd.service; enabled) Active: active (running) since Fri 2015-08-14 10:17:20 CST; 2s ago Docs: man:libvirtd(8) http://libvirt.org Main PID: 31850 (libvirtd) CGroup: /system.slice/libvirtd.service └─31850 /usr/sbin/libvirtd --listen Aug 14 10:17:20 localhost.localdomain systemd[1]: Started Virtualization daemon.
發現沒有問題出現了，嘗試執行 virsh list 命令，也OK了：
[root@localhost ~]# virsh list
Id Name State
----------------------------------------------------
最后，啟動openstack-nova-compute，也不再出現最初的錯誤了。