问题说明：
在openstack上创建虚拟机，之前已顺利创建了n个centos6.8镜像的vm
现在用ubuntu14.04镜像创建vm，发现vm创建后的状态为ERROR！
1）终端命令行操作vm创建
[root@linux-node2 src]# nova boot --flavor kvm002 --image ubuntu-14.04 --nic net-id=3a5cef6e-2c12-4f26-938c-5d343edc91b3 --security-group default --key-name mykey kvm-ubuntu01
+--------------------------------------+-----------------------------------------------------+
| Property | Value |
+--------------------------------------+-----------------------------------------------------+
| OS-DCF:diskConfig | MANUAL |
| OS-EXT-AZ:availability_zone | |
| OS-EXT-SRV-ATTR:host | - |
| OS-EXT-SRV-ATTR:hypervisor_hostname | - |
| OS-EXT-SRV-ATTR:instance_name | instance-00000006 |
| OS-EXT-STS:power_state | 0 |
| OS-EXT-STS:task_state | scheduling |
| OS-EXT-STS:vm_state | building |
| OS-SRV-USG:launched_at | - |
| OS-SRV-USG:terminated_at | - |
| accessIPv4 | |
| accessIPv6 | |
| adminPass | 97FNEj25qDHw |
| config_drive | |
| created | 2016-10-31T06:01:15Z |
| flavor | kvm002 (38d2c062-3fc5-4fc8-9bef-3cf16a7cf6d0) |
| hostId | |
| id | 898363d4-b5df-4603-80f3-299bba76f79c |
| image | ubuntu-14.04 (25fa5e72-5e10-4500-905a-82eda30dca21) |
| key_name | mykey |
| metadata | {} |
| name | kvm-ubuntu01 |
| os-extended-volumes:volumes_attached | [] |
| progress | 0 |
| security_groups | default |
| status | BUILD |
| tenant_id | 0cd3632df93d48d6b2c24c67f70e56b8 |
| updated | 2016-10-31T06:01:15Z |
| user_id | 52ba7917bb284af7ad6ac313b7e8e948 |
+--------------------------------------+-----------------------------------------------------+
创建后，发现vm的状态是ERROR
[root@linux-node2 src]# nova list
+--------------------------------------+--------------+--------+------------+-------------+----------+
| ID | Name | Status | Task State | Power State | Networks |
+--------------------------------------+--------------+--------+------------+-------------+----------+
| 898363d4-b5df-4603-80f3-299bba76f79c | kvm-ubuntu01 | ERROR | - | NOSTATE | |
+--------------------------------------+--------------+--------+------------+-------------+----------+
2）尝试在openstack的dashboard界面里创建vm(即：“计算”->“实例"->"启动云主机")，如果vm创建失败，则会显示错误信息。
如上图，报错信息：
Flavor's disk is too small for requested image. Flavor disk is 16106127360 bytes, image is 21474836480 bytes.].
说明创建vm时所使用的Flavor(云主机类型)的磁盘空间不满足image镜像要求！本案例是说kvm002（15G）的根磁盘不满足ubuntu-14.04（openstack界面-“镜像”查看此镜像大小是25G）镜像大小。
查看创建vm所使用的Flavor的类型
解决办法：
调整对应Flavor类型的跟磁盘大小(即："系统"->"云主机类型"->"编辑云主机类型"->"主机类型信息")。如下，由原来的15G调整到30G！
最后，再次尝试创建vm：
[root@linux-node2 src]# nova boot --flavor kvm002 --image ubuntu-14.04 --nic net-id=3a5cef6e-2c12-4f26-938c-5d343edc91b3 --security-group default --key-name mykey kvm-ubuntu01
+--------------------------------------+-----------------------------------------------------+
| Property | Value |
+--------------------------------------+-----------------------------------------------------+
| OS-DCF:diskConfig | MANUAL |
| OS-EXT-AZ:availability_zone | |
| OS-EXT-SRV-ATTR:host | - |
| OS-EXT-SRV-ATTR:hypervisor_hostname | - |
| OS-EXT-SRV-ATTR:instance_name | instance-00000006 |
| OS-EXT-STS:power_state | 0 |
| OS-EXT-STS:task_state | scheduling |
| OS-EXT-STS:vm_state | building |
| OS-SRV-USG:launched_at | - |
| OS-SRV-USG:terminated_at | - |
| accessIPv4 | |
| accessIPv6 | |
| adminPass | 97FNEj25qDHw |
| config_drive | |
| created | 2016-10-31T06:01:15Z |
| flavor | kvm002 (38d2c062-3fc5-4fc8-9bef-3cf16a7cf6d0) |
| hostId | |
| id | 898363d4-b5df-4603-80f3-299bba76f79c |
| image | ubuntu-14.04 (25fa5e72-5e10-4500-905a-82eda30dca21) |
| key_name | mykey |
| metadata | {} |
| name | kvm-ubuntu01 |
| os-extended-volumes:volumes_attached | [] |
| progress | 0 |
| security_groups | default |
| status | BUILD |
| tenant_id | 0cd3632df93d48d6b2c24c67f70e56b8 |
| updated | 2016-10-31T06:01:15Z |
| user_id | 52ba7917bb284af7ad6ac313b7e8e948 |
+--------------------------------------+-----------------------------------------------------+
创建虚拟机后，发现vm可以正常启动了！
[root@linux-node2 src]# nova list
+--------------------------------------+--------------+--------+------------+-------------+--------------------+
| ID | Name | Status | Task State | Power State | Networks |
+--------------------------------------+--------------+--------+------------+-------------+--------------------+
| 729dd327-3447-42b9-b9cb-e7ef4a38b725 | kvm-ubuntu01 | ACTIVE | - | Running | flat=192.168.1.120 |
+--------------------------------------+--------------+--------+------------+-------------+--------------------+
------------------------------------------------------------------------------------------------------------------------------
问题：在一个计算节点上创建虚拟机，创建前几个虚拟机都没问题，但是再创建第n个虚拟机时就失败，报错如下：
创建云主机，状态错误，无法启动，提示NoValidHost: No valid host was found. There are not enough hosts available.
查看nova-conductor.log，如下：
[root@linux-node2 nova]# pwd
/var/log/nova
[root@linux-node2 nova]# tail -100 nova-conductor.log
...................
2016-11-01 01:28:38.889 51843 WARNING nova.scheduler.utils [req-9eb2b8ec-216b-4073-95bd-1fbb51844faf 52ba7917bb284af7ad6ac313b7e8e948 0cd3632df93d48d6b2c24c67f70e56b8 - - -] Failed to compute_task_build_instances: No valid host was found. There are not enough hosts available.
Traceback (most recent call last):
File "/usr/lib/python2.7/site-packages/oslo_messaging/rpc/server.py", line 142, in inner
return func(*args, **kwargs)
File "/usr/lib/python2.7/site-packages/nova/scheduler/manager.py", line 84, in select_destinations
filter_properties)
File "/usr/lib/python2.7/site-packages/nova/scheduler/filter_scheduler.py", line 90, in select_destinations
raise exception.NoValidHost(reason=reason)
NoValidHost: No valid host was found. There are not enough hosts available.
2016-11-01 01:28:38.889 51843 WARNING nova.scheduler.utils [req-9eb2b8ec-216b-4073-95bd-1fbb51844faf 52ba7917bb284af7ad6ac313b7e8e948 0cd3632df93d48d6b2c24c67f70e56b8 - - -] [instance: 2211eeb4-9d06-4b15-ac15-69cdabe280ff] Setting instance to ERROR state.
这个问题产生的很大原因有：
1）计算节点的内存不足、CPU资源不够、硬盘空间资源不足造成的；将云主机类型规格调小点，发现就能创建成功。
2）网络配置不正确，造成创建虚拟机的时候获取ip失败；网络不通或防火墙引起。
3）openstack-nova-compute服务状态问题。可以尝试重启控制节点的nova相关服务和计算节点的openstack-nova-compute服务；详细检查控制节点和计算节点的nova.conf配置是否有不当配置。
4）这个报错问题的原因很多，具体要查看/var/log/nova下的日志详细分析。重点是nova-compute.log、nova-conductor.log日志
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在部署openstack虚拟机的时候，要注意以下几点：
（1）控制节点和计算节点在部署前，需要在/etc/hosts里面对主机映射，并且后面不能轻易更改，否则会出问题！
（2）mysql的连接数要调大！否则在操作过程中会由于mysql连接数过多而中断！比如设置mysql连接数为1000，mysql命令为set GLOBAL max_connections=1000;
（3）在创建vm的时候，要保证openstack节点的内存够用。
（4）所使用的Flavor云主机类型配置的根磁盘要满足image镜像的空间。