Sometimes you want to know if the network cable is plug but you don’t want to go to the server room.
In my case it was the eth2 interface.
First check if the interface is well connected and detected by the kernel:
$ cat /proc/net/dev | grep eth2
eth2: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
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Now check the connection status:
$ grep "" /sys/class/net/eth2/operstate
down
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See an ordered list of all parameters:
$ grep "" /sys/class/net/eth2/*
/sys/class/net/eth2/addr_assign_type:0
/sys/class/net/eth2/address:00:04:23:ad:98:a4
/sys/class/net/eth2/addr_len:6
/sys/class/net/eth2/broadcast:ff:ff:ff:ff:ff:ff
grep: /sys/class/net/eth2/carrier: Invalid argument
/sys/class/net/eth2/dev_id:0x0
grep: /sys/class/net/eth2/dormant: Invalid argument
grep: /sys/class/net/eth2/duplex: Invalid argument
/sys/class/net/eth2/flags:0x1002
/sys/class/net/eth2/ifindex:4
/sys/class/net/eth2/iflink:4
/sys/class/net/eth2/link_mode:0
/sys/class/net/eth2/mtu:1500
/sys/class/net/eth2/netdev_group:0
/sys/class/net/eth2/operstate:down
grep: /sys/class/net/eth2/speed: Invalid argument
/sys/class/net/eth2/tx_queue_len:1000
/sys/class/net/eth2/type:1
/sys/class/net/eth2/uevent:INTERFACE=eth2
/sys/class/net/eth2/uevent:IFINDEX=4
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The Invalid argument seems logic since the interface is not connected
You can also simply check the kernel logs like so:
$ dmesg | grep eth2
[ 1.174034] e1000 0000:04:02.0: eth2: (PCI-X:133MHz:64-bit) 00:04:23:ad:98:a4
[ 1.174042] e1000 0000:04:02.0: eth2: Intel(R) PRO/1000 Network Connection
[ 5.940934] ADDRCONF(NETDEV_UP): eth2: link is not ready
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At the end, I went to the server room…
Can be useful :)
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