xenstore

Xenstore 是主要的用来控制建立来自客户机的共享内存区域的事件通道、管理客户机的通知，收集客户机状态数据的工具。Xenstore 的目录是层次似的 key-data 值对。每个域都有一个目录继承结构，包含存储它自身的信息，主要是配置信息。

这些信息一般存储于一个数据库中，位于 /var/lib/xenstored/tdb。都是关于和域方面有关的关键功能。比如，一个Xen 总线在安装新的硬件时能方便发现新的硬件。这对于客户机的热拔插功能是很关键的。维护一个域的配置信息只是更新在存储继承结构中的引用。由于域只能修改自 身目录的内容，它们被允许注册而收到有关和它们存储的树结构的修改的通知。比如你要将一个客户机从使用主机的 CD-ROM 驱动器到使用一个 ISO 文件，你将需要使用管理工具来更新域的存储信息，使得其中 /dev/cdrom 的配置重新映射到一个 ISO 文件。这并不需要域的重新创建。

如果你查看这种继承结构，将会看到 3 个主要的路径：
/vm：包含和域相关的配置；
/local/domain：本节点上存储的信息；
/tool：包含不同用户模态下的工具。

你可以使用这些信息来开发一个定制的管理接口或者进行 Xen 环境下简单的查询。下面几个命令是和此有关的：
xenstore-chmod：准许管理员和开发人员手工改变 Xenstore 中任意位置的权限；
xenstore-list：列出存放于目录中存放的 key，或者类别。
xenstore-read：输出和一个特定 key 有关的值。
xenstore-write：改变 key 中存放的值。
xenstore-exists：用于检查一个特定的 key-value 是否存在。
xenstore-ls：输出整个数据库树，包含所有的节点和key-value 值对。
xenstore-rm：删除一个 key。

#!/bin/sh

 

function dumpkey()

{

    local param=${1}

    local key

    local result

    result=$(xenstore-list ${param})

    if [ "${result}" != "" ] ; then

        for key in ${result} ; do dumpkey ${param}/${key} ; done

    else

        echo -n ${param}'='

        xenstore-read ${param}

    fi

}

 

for key in /vm /local/domain /tool; do dumpkey ${key} ; done

或者你直接运行 xenstore-ls 打出整个数据库的树状结构：

tool = ""

 xenstored = ""

vm = ""

 00000000-0000-0000-0000-000000000000 = ""

  shadow_memory = "0"

  uuid = "00000000-0000-0000-0000-000000000000"

  on_reboot = "restart"

  on_poweroff = "destroy"

  name = "Domain-0"

  xend = ""

   restart_count = "0"

  vcpus = "2"

  vcpu_avail = "3"

  memory = "2516"

  on_crash = "restart"

  maxmem = "2651"

 8059729a-360a-0793-39d5-05bd058cf587 = ""

  image = "(linux (ramdisk /var/lib/xen/boot_ramdisk.z1pw6p) (kernel /var/li..."

   ostype = "linux"

   kernel = "/var/lib/xen/boot_kernel.vkUxRH"

   cmdline = " ro root=LABEL=/"

   ramdisk = "/var/lib/xen/boot_ramdisk.z1pw6p"

  device = ""

   vkbd = ""

    0 = ""

     frontend = "/local/domain/1/device/vkbd/0"

     frontend-id = "1"

     backend-id = "0"

     backend = "/local/domain/0/backend/vkbd/1/0"

   tap = ""

    51712 = ""

     frontend = "/local/domain/1/device/vbd/51712"

     frontend-id = "1"

     backend-id = "0"

     backend = "/local/domain/0/backend/tap/1/51712"

   vif = ""

    0 = ""

     frontend = "/local/domain/1/device/vif/0"

     frontend-id = "1"

     backend-id = "0"

     backend = "/local/domain/0/backend/vif/1/0"

    1 = ""

     frontend = "/local/domain/1/device/vif/1"

     frontend-id = "1"

     backend-id = "0"

     backend = "/local/domain/0/backend/vif/1/1"

   vfb = ""

    0 = ""

     frontend = "/local/domain/1/device/vfb/0"

     frontend-id = "1"

     backend-id = "0"

     backend = "/local/domain/0/backend/vfb/1/0"

  shadow_memory = "0"

  uuid = "8059729a-360a-0793-39d5-05bd058cf587"

  on_reboot = "restart"

  start_time = "1235966971.63"

  on_poweroff = "destroy"

  name = "test2"

  xend = ""

   restart_count = "0"

  vcpus = "1"

  vcpu_avail = "1"

  memory = "512"

  on_crash = "restart"

  maxmem = "512"

local = ""

 domain = ""

  0 = ""

   vm = "/vm/00000000-0000-0000-0000-000000000000"

   device = ""

   control = ""

   error = ""

    backend = ""

     tap = ""

      1 = ""

       51712 = ""

        error = "2 getting info"

   cpu = ""

    0 = ""

     availability = "online"

    1 = ""

     availability = "online"

   memory = ""

    target = "2576384"

   name = "Domain-0"

   console = ""

    limit = "1048576"

   domid = "0"

   backend = ""

    vkbd = ""

     1 = ""

      0 = ""

       frontend-id = "1"

       domain = "test2"

       frontend = "/local/domain/1/device/vkbd/0"

       state = "4"

       online = "1"

       feature-abs-pointer = "1"

       hotplug-status = "connected"

    tap = ""

     1 = ""

      51712 = ""

       domain = "test2"

       frontend = "/local/domain/1/device/vbd/51712"

       format = "raw"

       dev = "xvda"

       state = "4"

       params = "aio:/root/test2"

       mode = "w"

       online = "1"

       frontend-id = "1"

       type = "tap"

       sectors = "12582912"

       sector-size = "512"

       info = "0"

       hotplug-status = "connected"

    vif = ""

     1 = ""

      0 = ""

       bridge = "xenbr0"

       domain = "test2"

       handle = "0"

       script = "/etc/xen/scripts/vif-bridge"

       state = "4"

       frontend = "/local/domain/1/device/vif/0"

       mac = "00:16:3e:20:ca:9b"

       online = "1"

       frontend-id = "1"

       feature-sg = "1"

       feature-gso-tcpv4 = "1"

       feature-rx-copy = "1"

       hotplug-status = "connected"

      1 = ""

       bridge = "xenbr0"

       domain = "test2"

       handle = "1"

       script = "/etc/xen/scripts/vif-bridge"

       state = "4"

       frontend = "/local/domain/1/device/vif/1"

       mac = "00:16:3e:65:15:b6"

       online = "1"

       frontend-id = "1"

       feature-sg = "1"

       feature-gso-tcpv4 = "1"

       feature-rx-copy = "1"

       hotplug-status = "connected"

    vfb = ""

     1 = ""

      0 = ""

       vncunused = "0"

       domain = "test2"

       frontend = "/local/domain/1/device/vfb/0"

       xauthority = "/root/.Xauthority"

       vncdisplay = "0"

       state = "4"

       online = "1"

       frontend-id = "1"

       type = "vnc"

       hotplug-status = "connected"

       request-update = "1"

  1 = ""

   vm = "/vm/8059729a-360a-0793-39d5-05bd058cf587"

   device = ""

    vkbd = ""

     0 = ""

      protocol = "x86_32-abi"

      state = "4"

      backend-id = "0"

      backend = "/local/domain/0/backend/vkbd/1/0"

      page-ref = "776015"

      event-channel = "7"

      request-abs-pointer = "1"

    vbd = ""

     51712 = ""

      virtual-device = "51712"

      device-type = "disk"

      protocol = "x86_32-abi"

      backend-id = "0"

      state = "4"

      backend = "/local/domain/0/backend/tap/1/51712"

      ring-ref = "8"

      event-channel = "8"

    vif = ""

     0 = ""

      mac = "00:16:3e:20:ca:9b"

      handle = "0"

      protocol = "x86_32-abi"

      backend-id = "0"

      state = "4"

      backend = "/local/domain/0/backend/vif/1/0"

      tx-ring-ref = "1280"

      rx-ring-ref = "1281"

      event-channel = "9"

      request-rx-copy = "0"

      feature-rx-notify = "1"

      feature-sg = "1"

      feature-gso-tcpv4 = "1"

     1 = ""

      mac = "00:16:3e:65:15:b6"

      handle = "1"

      protocol = "x86_32-abi"

      backend-id = "0"

      state = "4"

      backend = "/local/domain/0/backend/vif/1/1"

      tx-ring-ref = "1282"

      rx-ring-ref = "1283"

      event-channel = "10"

      request-rx-copy = "0"

      feature-rx-notify = "1"

      feature-sg = "1"

      feature-gso-tcpv4 = "1"

    vfb = ""

     0 = ""

      protocol = "x86_32-abi"

      state = "4"

      backend-id = "0"

      backend = "/local/domain/0/backend/vfb/1/0"

      page-ref = "776025"

      event-channel = "6"

      feature-update = "1"

   control = ""

   error = ""

   device-misc = ""

    vif = ""

     nextDeviceID = "2"

   console = ""

    use_graphics = "1"

    ring-ref = "774877"

    port = "2"

    limit = "1048576"

    tty = "/dev/pts/0"

    vnc-port = "5900"

   name = "test2"

   domid = "1"

   cpu = ""

    0 = ""

     availability = "online"

   memory = ""

    target = "524288"

   store = ""

    ring-ref = "774878"

    port = "1"

   serial = ""

    0 = ""

     tty = "/dev/pts/0"

其中 xm list 的输出：

[root@chenyajun ~]# xm list

Name                                      ID Mem(MiB) VCPUs State   Time(s)

Domain-0                                   0     2516     2 r-----    140.5

test2                                      1      511     1 -b----     29.7