[Beowulf] Ethernet Status

[Gerry Creager n5jxs]

Once you determine what the device name is, I'd also recommend something 
like

ethtool eth0

to see the settings of that port.

gerry

Robert G. Brown wrote:
> On Tue, 24 May 2005, Paul Romero wrote:
> 
> 
>>Dear User Group:
>>
>>How does one determine the status of a device
>>such as eth0.   My initial guess is that once
>>you know the device name for eth0, you can
>>just open it and use ioctl calls, or perhaps it will
>>not successfully open if the hardware device is down.
>>
>>My problem is I can't figure out the device name.
>>(i.e. My motivation for doing this is to find out if
>>my system has physical IP connectivity without referencing
>>a particular IP address.)
> 
> 
> Hmmm, this sounds like the kind of question that suggests that it would
> be a good idea for you to get a book or two on linux from B&N or Amazon.
> 
> There are lots of ways to get information about the network.  All of the
> commands below are low level raw commands entered at a command line.
> For an individual workstation, one can often determine a lot of
> information using Win-like configuration GUIs (e.g.
> system-config-network in RH or Fedora), but these tools are too limiting
> to use as a cluster manager.
> 
> The most immediately useful is the command:
> 
>   /sbin/ifconfig
> 
> which shows you the status of your existing network and can be used to
> configure a network device (e.g. give it an IP number, netmask,
> broadcast address, and more).
> 
>   /sbin/route
> 
> is a companion to this that is often useful for resolving routing
> problems, which are as likely to be a problem as anything else if a
> network device doesn't work.
> 
>   cat /etc/resolv.conf
> 
> lets you see your current nameservice resolution table, in case you are
> having difficulty resolving hostnames; in a cluster environment you may
> well want to set up cluster nodenames in e.g. /etc/hosts.conf and turn
> on local hostname resolution in /etc/nsswitch.conf.  If you use dhcp and
> NIS though, most of this will be handled automagically for you, once you
> learn those somewhat more complicated tools for distributing network and
> host database information.
> 
> A >>very<< useful thing to learn to do is to read the system logs, which
> will usually show you attached devices when it probes them during boot.
> This presumes to some extent that the devices were at SOME time
> autoprobed or installed by hand in e.g. /etc/modprobe.conf, a file that
> maps specific device names (such as eth0) to kernel driver modules (such
> as e100).  
> 
>   /sbin/lsmod 
> 
> will show you whether the module associated with your network device is
> loaded -- it will generally autoload on demand when the network device
> is first initialized.  If your system was never probed, you can try
> adding lines to /etc/modprobe.conf by hand (if you know for sure what
> kind of network device you have) -- something like 
> 
>   alias eth0 e100
> 
> (where e100 is the name of the appropriate kernel module) might do it.
> Or run a probing tool.  In RH or Fedora this tool is "/usr/bin/kudzu".
> I have no idea what it might be in other flavors of linux.
> 
> To read the logs, use e.g.
> 
>   /usr/bin/less /var/log/messages
> 
> and look through the kernel's boot logs, /var/log/boot.log.?.  If a
> device is present but not initializing correctly, it will likely be
> traced out there.
> 
> Finally, there are certain places where the information that the kernel
> maintains about network devices can be read directly from the "raw"
> /proc interface.  Try looking at /proc/net/dev, for example.
> 
> There are a variety of higher end tools for displaying network device
> load (processed out of /proc data).  Try for example
> 
>   /bin/netstat -i 5
> 
> (and note the obvious connections to /proc/net/dev, "digested").
> netstat is a swiss-army-knife tool.  Read the man page to get some idea
> what it can do.
> 
> Hope this helps.
> 
>     rgb
> 
> 
>>Best Regards,
>>
>>Paul R.
>>
>>
>>--
>>Paul Romero
>>
>>RCOM Communications Software
>>
>>Phone/Fax: (510)339-2628
>>E-Mail: paulr at rcom-software.com
>>
>>
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> 
> 

-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020
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