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I currently have one computer (it's called pc08 with Linux Mint 15) that is connected to the internet via WLAN. Now I want to install Arch Linux on another computer (lets call it archiso).

I only have WLAN, but it seems to be quite difficult install Arch Linux with WLAN only. So I thought I could possibly provide a LAN internet connection like this:

 -----------------------
| pc08                  |
| has internet by WLAN  |
 -----------------------
            |
            |
    --------------
    | Switch      |
     -------------
            |
 -------------------------
 | archiso               |
 | has WLAN, but I cannot|
 | connect               |
  -----------------------

Is it possible to get an internet connection like this?

If it is possible: What do I have to do on both computers?

What I've done so far

I think I have to set up a DHCP server on pc08 while using the provided DHCP server from WLAN.

  • I've installed isc-dhcp-server.
  • Set INTERFACES="eth0″ in /etc/default/isc-dhcp-server
  • It seems as if I have to edit /etc/dhcp/dhcpd.conf, but I have no idea what are good options.
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  • Sounds like you're after the very typical "internet sharing" configuration (as windows called it once), or NAT to the technical world (SNAT specifically). Sharing a singular internet connection over a LAN, if thats what you're asking, is a widely publicised topic, have been doing it myself since 1994 on linux boxes. Now that you know it is called NAT, or sometimes masquerading, you should be able to find suitable howto's to guide you through it through the usual routes (aka google). – iain Oct 6 '13 at 21:44
  • I'll give you some specific additional guidance. The changes on the "router" (machine with internet and lan) are firewall related, iptables, and essentially guide traffic from the LAN through the SNAT system before the packets go out. I'm not going to give you the "one line version" of that command because you oughta set up your iptables completely with firewalling and stuff, so a guide will guide you better hopefully. The changes on the client are zero directly, indirectly your DHCP configuration just needs to hand out suitable LAN IP's and set the default gateway to your router-pcs LAN IP – iain Oct 6 '13 at 21:47
  • Hmm ... I've just noticed that ifconfig gives only lo and wlp4s0 on the archiso machine. Does this mean the network card is broken / a driver is missing? – Martin Thoma Oct 6 '13 at 22:07
  • However, lspci shows an Ethernet controller. But ifconfig eth0 up gives "eth0: ERROR while getting interface flags: no such device". – Martin Thoma Oct 6 '13 at 22:10
  • Ok, found the problem and solution: Arch linux Broadcom BCM57780 – Martin Thoma Oct 6 '13 at 22:19
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The answer to the question

Open network manager:

enter image description here

Set the wired connection to shared:

enter image description here

That's it. No need to change anything else, when the ethernet works on the new computer

The real problem

Ethernet did not work. How do you get to know this? With ifconfig:

moose@pc08 ~ $ ifconfig
eth0      Link encap:Ethernet  HWaddr e8:40:f2:93:ff:ab  
          inet addr:10.42.0.1  Bcast:10.42.0.255  Mask:255.255.255.0
          inet6 addr: fe80::ea40:f2ff:fe93:ffab/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:14 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1139 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1716 (1.7 KB)  TX bytes:280048 (280.0 KB)
          Interrupt:17 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:30300 errors:0 dropped:0 overruns:0 frame:0
          TX packets:30300 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:3042922 (3.0 MB)  TX bytes:3042922 (3.0 MB)

wlan0     Link encap:Ethernet  HWaddr 9c:b7:0d:f1:35:65  
          inet addr:192.168.178.64  Bcast:192.168.178.255  Mask:255.255.255.0
          inet6 addr: fe80::9eb7:dff:fef1:3565/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:724007 errors:0 dropped:0 overruns:0 frame:0
          TX packets:510402 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:903500289 (903.5 MB)  TX bytes:72202555 (72.2 MB)

If there is no eth0, this might indicate that there is a problem. Then you can check this:

moose@pc08 ~ $ lspci | grep Ethernet
03:00.0 Ethernet controller: Broadcom Corporation NetLink BCM57780 Gigabit Ethernet PCIe (rev 01)

In my case, I had to load some Kernel modules in the right order.

After that, I could do this:

cp /etc/netctl/examples/ethernet-dhcp /etc/netctl/eth0-dhcp
netctl start eth0-dhcp

I had to adjust eth0 in ethernet-dhcp to my name (that showed up in ifconfig). Finally done.

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