(转)Linux 远程开机（walk on lan）

一，什么情况下需要远程开机？
   如果我们的服务器没有部署在本地（实际上通常都是这样的，我们会把服务器托管到IDC机房），
  而且服务器在机房中不止一台，其中一台被关闭时，则我们可以远程连接一台没有关机的服务器上，
  然后进行远程开机.
 
二，远程开机需要的软件
    它需要wakeonlan这个软件，
    从何处得到它？
    它的官方站是：http://sourceforge.net/projects/wake-on-lan/
    如果使用rpm包可以从这里下载：http://dag.wieers.com/rpm/packages/wol/
    如果使用fedora，则可以用yum命令安装:
    yum install wol
   
三，如何进行远程开机？
   先不要急着去关闭你的linux服务器，你首先要确定它是否支持远程开机？
  第一步：登录到目标服务器，用ethtool这个命令打印出网卡的信息
        [root@localhost lhd]# ethtool eth0
        Settings for eth0:
        Supported ports: [ TP MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
        Advertised auto-negotiation: Yes
        Speed: 100Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 32
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: pumbg
        Wake-on: d
        Current message level: 0x00000007 (7)
        Link detected: yes

        可以看到，ethtool把网卡的信息全部列出，我们只关心其中的这两项:
        Supports Wake-on: pumbg
        Wake-on: d
          如果 wake-on 一项值为 d,表示禁用wake on lan
                         值为 g,表示启用 wake on lan
                             
    因为此机器禁用了 wake on lan,所以用下面的命令来启用它:
    [root@localhost lhd]# ethtool -s eth0 wol g

    再用 ethtool命令进行查看,会发现:
    Wake-on: g
            
    OK，目标机器的网卡已经支持了远程开机，下面我们得到它的本地MAC地址:
    [root@localhost lhd]# ifconfig
          eth0      Link encap:Ethernet  HWaddr 00:03:0D:1D:1F:97
          inet addr:192.168.6.101  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:34470 errors:0 dropped:0 overruns:0 frame:0
          TX packets:35377 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:31559763 (30.0 MiB)  TX bytes:5340032 (5.0 MiB)
          Interrupt:5 Base address:0x2c00
    把HWaddr 00:03:0D:1D:1F:97这一项记录下来即可

    现在你可以试着把目标机器关闭


  第二步：开机

     现在我们需要登录到已安装了wakeonlan软件的机器上，在上面执行开机命令:
     
     wol 00:03:0D:1D:1F:97
     稍后就会发现，目标机器已开机可以登录了

Ethernet Interface Settings

ethtool is a program that displays and changes Ethernet card settings such as auto-negotiation, port speed, duplex mode, and Wake-on-LAN. It is not installed by default, but is available for installation in the repositories.

sudo apt-get install ethtool

The following is an example of how to view supported features and configured settings of an Ethernet interface.

sudo ethtool eth0
Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Half 1000baseT/Full 
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Half 1000baseT/Full 
        Advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: d
        Current message level: 0x000000ff (255)
        Link detected: yes

Changes made with the ethtool command are temporary and will be lost after a reboot. If you would like to retain settings, simply add the desired ethtool command to a pre-up statement in the interface configuration file /etc/network/interfaces.

The following is an example of how the interface identified as eth0 could be permanently configured with a port speed of 1000Mb/s running in full duplex mode.

auto eth0
iface eth0 inet static
pre-up /usr/sbin/ethtool -s eth0 speed 1000 duplex full