# no loopback device [SOLVED]

## crashgen

Hi ppl

I noticed that my loopback device doesn't exist:

# ifconfig lo up

lo: unknown interface: No such device

I noticed that because I cant print. Printserver does not initialize.. :S

This problem is new because at some time ago I started loopback and I printed documents as I wanted. No problem at all.

Anybody can help?

Thanks  :Wink: Last edited by crashgen on Sat Oct 14, 2006 1:29 pm; edited 1 time in total

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## exklusve

have you upgraded your kernel lately?

There is a loopback device in the kernel config.   Might wanna check that out.

I cant recall off the top of my head where in the config that is.  

Grep is your friend  :Wink: 

hope that helps

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## wynn

It looks as if it is enabled by

```
CONFIG_INET:

These are the protocols used on the Internet and on most local

Ethernets. It is highly recommended to say Y here (this will enlarge

your kernel by about 144 KB), since some programs (e.g. the X window

system) use TCP/IP even if your machine is not connected to any

other computer. You will get the so-called loopback device which

allows you to ping yourself (great fun, that!).

Symbol: INET [=y]

 Prompt: TCP/IP networking

   Defined at net/Kconfig:41

   Depends on: NET

   Location:

     -> Networking

       -> Networking support (NET [=y])

         -> Networking options

   Selected by: OCFS2_FS && NET && SYSFS && EXPERIMENTAL
```

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## crashgen

yes its enable.. I may have recompiled kernel but I think that I didn't changed any networking option..

Look at my config:

 Symbol: INET [=y]                                                                                 

  │ Prompt: TCP/IP networking                                                                         

  │   Defined at net/Kconfig:34                                                                       

  │   Depends on: NET                                                                                 

  │   Location:                                                                                       

  │     -> Networking                                                                                 

  │       -> Networking support (NET [=y])                                                            

  │         -> Networking options                                                                    

.. I have loopback support at block drivers as module. I load module loop.ko but I dont have loopback device anyway.. :S

thanks!

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## crashgen

I changed loopback support from module to kernel image. Reboot and no loopback again.

```
laptop init.d # ifconfig lo up

lo: unknown interface: No such device
```

please help :S

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## wynn

The block loop device is something different, see 'man losetup' for a short explanation.

The net loopback device is that associated with the IP address 127.0.0.1 (and others in this range I believe).

/etc/init.d/net.lo should set this up, you should have

```
# rc-update show | grep net.lo

              net.lo | boot
```

and net.eth0 and so on should be symbolic links to it.

/etc/init.d/net.lo is part of sys-apps/baselayout.

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## crashgen

yes u are right sorry!

Now I can notice an error:

```
laptop init.d # rc-update show | grep net.lo

 * Broken runlevel entry: /etc/runlevels/boot/net.lo

              net.lo | boot
```

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## crashgen

I have fixed all boot and default runlevels:

```
laptop ck # rc-update show

            bootmisc | boot

             checkfs | boot

           checkroot | boot

               clock | boot

            coldplug |      default

         consolefont | boot

               cupsd |      default

            hostname | boot

             hotplug |      default

             keymaps | boot

               local |      default nonetwork

          localmount | boot

             modules | boot

            net.eth0 |      default

              net.lo | boot default

           rmnologin | boot

              splash | boot default

           syslog-ng |      default

             urandom | boot

          vixie-cron |      default

              vmware |      default

                 xdm |      default
```

But I still dont have lo working.. :S

```
laptop ck # ifconfig lo up

lo: unknown interface: No such device
```

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## wynn

If you have a "Broken runlevel entry" then you need to do

```
cd /etc/runlevels/boot

rm net.lo

rc-update add net.lo boot
```

You now have net.lo in both boot and default which isn't right: to remove it from default

```
rc-update del net.lo default
```

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## crashgen

I have already solve that..

Now I have net.lo only in boot, but it looks like this:

```

laptop ck # /etc/init.d/net.lo restart

laptop ck #

laptop ck # /etc/init.d/net.lo status

 * status:  stopped

laptop ck # ifconfig lo up

lo: unknown interface: No such device
```

This is my problem now :S

thanks anywayLast edited by crashgen on Fri Oct 13, 2006 8:47 pm; edited 1 time in total

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## wynn

Could you paste your running kernel's .config to http://pastebin.ca, please? I won't be able to look at it until tomorrow though.

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## crashgen

My kernel .config:  http://pastebin.ca/201391

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## TheBear80

Hi crashgen,

I experience exactly the same problem this morning. In my case I found the solution in this thread. The problem was a downgrade of udev from ~x86 to x86 that left some rules behind. Hope that helps you too.

Greetings

Björn

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## wynn

 *crashgen wrote:*   

> My kernel .config:  http://pastebin.ca/201391

 Checking this is going to be a little bit difficult as it's a version (2.6.15) and subversion (suspend2) that I don't have a config for.

I'll wait and see what fruit TheBear80's suggestion yields if you don't mind   :Smile: 

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## crashgen

TheBear80  :Smile: 

Udev is always a problematic application.. :S. My ipw2200 wireless device realy hates udev grrr.. I had to choose a specified version of udev to make my wireless work. Now udev rules made loopback interface vanish :S

I cleaned all rules from /etc/udev/rules.d (mantained firmware.rules (ipw2200)) and reemerged udev-079-r2.

Know all works fine  :Wink:  thks

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