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Cannot resolve hostname

Former Member

I start by saying I am not a Linux expert, I am a competent MSDOS/Windows user willing to have a go at most things and I have wanted to try out Linux for a while but bee reluctant to install it on my PC. So when the Raspberry Pi was announced I had to have one.

 

I recently received my RasPi just before going on holiday I had previously bought some 4GB SD cards and set them up with different OS's as recommended on the website (http://www.raspberrypi.org/downloads).

 

I connected it up quickly just to have a look, I used both available USB sockets for the keyboard and mouse and a standard ethernet cable to my router, my screen is an old flat screen TV with no HD socket so the resolution was poor but it seemed to work fine, booted up OK logged in and accessed the internet. So I went on holiday happy.

 

On my return I decided to setup as suggested with a cheap powered USB hub. It has now taken me about a week on and off to get it working properly again, so I offer my story in the hope that it will help some one else avoid the same problem.

 

The Problem

On switch on the RasPi boots OK logs in OK Startx runs OK, everything seems to work except the internet. On boot up you can open a terminal window and ping the router OK, when you run the ifconfig command you get what appears to me to be a good response, it identifies the network address of the RasPi correctly as it can be seen from the router. But at no point can I access the internet. The Midori browser runs OK but fails to access any website, you get "Cannot resolve hostname...." or other similar messages. I could not easily find any settings to adjust to rectify the problem. After a short while the ping to the router stopped working and the router itself stated the the RasPi was not connected.

 

I spent hours trying different SDRAM cards with different OS's, switched out all the cables one at a time, I even looked into various online forums to see if anyone else had had the same problem. I Googled every error message I received looking for guidance, nothing. I tried a wireless USB adapter, even connected it directly to the router with no other computer connected.

 

In short I tried more potential fixes than I care to remember, I am not a Linux expert as I say but I felt that it had to be something I was doing, no one else seemed to have this problem and the RasPi was working all but the internet.

 

The Solution?

In the end I reverted back to connecting the keyboard and mouse directly to the RasPi without the powered USB hub (I should have realised ages ago but it still doesnt make sense) It worked fine!!

 

Tried a basic unpowered hub that also works fine, I am now been able to access the internet and Ping the RasPi from my windows PC all of which I couldnt do before.

 

This episode has been very useful for me, I am now much more familiar with Linux than I was, however as for the underlying cause I am stumped. If anyone can explain the behaviour of the powered USB hub or anything else I have done please let me know. I submit this post for those like me who are just starting and may have the same problem, if you find it useful let me know.

 

Mick Hollywood

  • Well Mick, don't feel bad about being stumped by your problem.  It's certainly not a Linux issue --- I've been working with Unix since the late 70's when I'd get the sources on mag tape from Bell Labs to run on a PDP-11, but no amount of *nix experience is going to help one diagnose that kind of nutty problem.

     

    Pi is somewhat unique in the problems it fosters owing to its odd choice of power source and  poor power management design, and those problems often just don't make sense when one has the expectation that everything that has been plugged in has enough power.

     

    I sure hope a future Pi redesign does things rather more robustly.  That means adding a barrel connector for power input, specifying a minimum 1A @ 5V power requirement (and it could be argued that it should be 1.5A recommended for headroom), and replacing the linear regulators and polyfuses by a proper power management IC with LDOs.

     

    Morgaine.

  • There is a list of "Problem USB Hubs" at the RasPi Wiki, some of which have Ethernet issues: http://elinux.org/RPi_VerifiedPeripherals#Problem_USB_Hubs.  You may want to add yours to the list.

     

    It's bizarre that your hub or the others listed would misbehave like that.  I suspect it's a problem with the USB driver, which according to reports has various issues such as using 20% of CPU time in its usual configuration.  I've read that the USB host controller in the BCM2835 SoC requires software to do things that are normally handled in hardware, which is why it uses so much CPU.  I've also read that the low-level driver for the controller is extremely difficult to understand, so who knows when or if these problems will ever be resolved.

  • in reply to johnbeetem

    John, such USB issues are one reason why I'm giving preference these days to boards which use a SoC that provides on-chip Ethernet MAC.  Although it depends on the intended application, networking is typically  too important for me to be done over USB, and there's more to the issue than simply thinking "480 > 100 so it's OK".  At gigabit rates the problems of USB are likely to get still worse.

     

    Of the cheap-end boards I've examined, only BeagleBone and APC seem to provide on-SoC Ethernet MAC, which is surprising when one considers that very cheap microcontrollers often provide it so an up-market applications processor really ought to if networking is intended.  Sadly, the Allwinner A13 doesn't have on-SoC Ethernet MAC (whereas the A10 did), so I think we're soon going to be seeing a large number of cheap Linux boards  that aren't quite as good at networking as they might have been.

     

    Morgaine.

  • Hi Mick,

                  Thank you for the information, we are in the same page, I just started yesterday and I had the same issue, I am a windows user and trying to learn Linux, I had the same issue, but because I do not know where to look for the MAC ID as I have some network filter with my router, there are 2 members who are very helpful that leads me the way.  The power supply that and using is from the Power Supply of my IPAD 64Gb and so fare no issue at all, I am also using wireless keyboard and mouse together that uses only one USB dongle so I still have one USB available with my PI, again thanks for sharing.

     

    Best regards,

     

    clem

  • Configure DNS properly , i faced a similar problem, it got corrected after using DNS, also weather u r using WiFi or Ethernet ,

    if Ethernet configure DNS for Static IP Configuration !