如何在 Linux 中檢查乙太網埠的物理狀態？

我想檢查指定的 ethX 物理上是向上還是向下。如何使用命令行執行此操作？

$ ethtool <eth?>

例如：

$ ethtool eth0

提供：

Settings for eth0:
       Supported ports: [ TP ]
       Supported link modes:   10baseT/Half 10baseT/Full
                               100baseT/Half 100baseT/Full
                               1000baseT/Full
       Supports auto-negotiation: Yes
       Advertised link modes:  10baseT/Half 10baseT/Full
                               100baseT/Half 100baseT/Full
                               1000baseT/Full
       Advertised pause frame use: No
       Advertised auto-negotiation: Yes
       Speed: 1000Mb/s
       Duplex: Full
       Port: Twisted Pair
       PHYAD: 1
       Transceiver: internal
       Auto-negotiation: on
       MDI-X: on
       Supports Wake-on: pumbg
       Wake-on: g
       Current message level: 0x00000001 (1)
       Link detected: yes

引用自：https://serverfault.com/questions/15776