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Changes between Version 11 and Version 12 of Automatic_Bridge_Ubuntu

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klaus (IP: 88.79.199.2)
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2008-01-21 20:12:47 (2 years ago)
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  • Automatic_Bridge_Ubuntu

    v11 v12  
    11== HOWTO Automatically configure bridge interfaces on !VirtualBox == 
    22 
    3 Version: 0.1[[BR]] 
    4 Author: Antonio Augusto da Silva (a.k.a. !KhaoticMind)[[BR]] 
    5 Date: 2007/03/16[[BR]] 
     3NOTE: This page used to describe how to set up bridging with old Ubuntu versions (up to 6.10) and old !VirtualBox versions (up to 1.3.x). As this is no longer useful except for a very small group of users, this information has been removed to avoid problems. Please read the manual about how to set up host interface networking, it contains Ubuntu/Debian-specific descriptions. 
    64 
    7 NOTE: as of kernel 2.6.18 and later (i.e. with Ubuntu 7.04) this stopped working, as now normal users are no longer allowed to dynamically create TAP devices. See the !VirtualBox user manual for details of how to do this is done in current versions of !VirtualBox (1.4.0 and later). 
    8  
    9 = 1. Introduction = 
    10  
    11 This is a quick tutorial on how to setup your Linux environment and !VirtualBox, 
    12 so that it can automatically create network interfaces and put them in bridge 
    13 when the VM is launched. 
    14  
    15 In fact the Vbox User Manual has all the details that you need to accomplish it, but I thought it would be better to give some more "hands on" for you guys ;)  
    16  
    17 I've tested this setup in my home computer, running Kubuntu 6.10. I've an ADSL 
    18 modem to which I connect through my eth0 port. The modem has DHCP, so I get my IP automatically.  
    19  
    20 = 1.1 What is bridging anyway? = 
    21  
    22 Well... I thought you would already know it (since you are reading this howto). 
    23 But hey... let me try to give you a brief explanation. Bridging in the sense we 
    24 are working here, is to configure your computer, so that, some (or all), of the 
    25 networks it has connected to it will look like they are in fact one single 
    26 network. 
    27  
    28 One example of its use is if you have a notebook that can connect to your home 
    29 computer through a wireless adapter and the home computer is also connect to the Internet (or to any other network) through a cable. To make the notebook able to access the Internet you have to options: routing(ref 1) and bridging(ref 2). Both solutions will work, but if you do routing only TCP/IP packets will be able to be exchanged (ok, ok, 90% of the world uses TCP/IP but hang with me). On the other hand bridging will give you a lot more of flexibility, since now the notebook will appear is it were direct connect to the other network, just like you. Doing so the notebook can then get its own IP address with DHCP, and you (and anybody on the same network than you) will be able to exchange any packet with the notebook without any problem. 
    30  
    31 What happens here is that your computer was turned in a Switch (or a HUB), and 
    32 simple connects all machines that are connected to it, like you had cables connection every one of them. To do this on linux you create a "virtual" interface, that will be the actual bridge, and simple "plug" all interfaces you 
    33 want to be connect to it. So what we will do here is configure a single bridge, and say that our network interface (usually eth0), and all network interfaces created by the VMs, will be connected to it. 
    34  
    35 = 1.2 Prerequisites = 
    36  
    37 Before continuing the first thing you're going to need is make sure you have 
    38 tunctl and brctl in your machine (the program `VBoxTunctl` is shipped with !VirtualBox starting from version 1.4.0). These are the programs that we will use in the next sections to create our virtual interfaces and our bridge. 
    39  
    40 In Ubuntu these two programs are on the uml-utilities and bridge-utils packages, respectively. 
    41  
    42 To install these packages issue the following command: 
    43  
    44 {{{ 
    45 sudo apt-get install bridge-utils uml-utilities 
    46 }}} 
    47  
    48 = 2. Configuring the bridge = 
    49  
    50 Ok, so lets start with the fun ;) 
    51  
    52 First of all, lets configure the network setup so that you will have a br0 
    53 interface at boot, and your network interface (eth0) will be part of it. 
    54  
    55 To accomplish this in Ubuntu I've configured my /etc/network/interfaces to look 
    56 something like this: 
    57  
    58 {{{ 
    59 auto br0 
    60 iface br0 inet dhcp 
    61        bridge_ports eth0 
    62  
    63 auto eth0 
    64 iface eth0 inet manual 
    65 }}} 
    66  
    67 Quite simple huh? With this setup you should have what we want. To test it 
    68 immediately run reinitialise the network: 
    69  
    70 {{{ 
    71 sudo /etc/init.d/networking restart 
    72 }}} 
    73  
    74 After it finish its job, doing an  
    75 {{{ 
    76 ifconfig 
    77 }}} 
    78  should show you something like this: 
    79  
    80 {{{ 
    81 br0        Encapsulamento do Link: Ethernet  Endereço de HW 00:11:D8:37:D8:B9 
    82           inet end.: 192.168.1.2  Bcast:192.168.1.255  Masc:255.255.255.0 
    83           endereço inet6: fe80::211:d8ff:fe37:d8b9/64 Escopo:Link 
    84           UP BROADCAST RUNNING MULTICAST  MTU:1500  Métrica:1 
    85           pacotes RX:6973 erros:0 descartados:0 excesso:0 quadro:0 
    86           Pacotes TX:7301 erros:0 descartados:0 excesso:0 portadora:0 
    87           colisões:0 txqueuelen:0 
    88           RX bytes:3557787 (3.3 MiB) TX bytes:932172 (910.3 KiB) 
    89  
    90 eth0       Encapsulamento do Link: Ethernet  Endereço de HW 00:11:D8:37:D8:B9 
    91           endereço inet6: fe80::211:d8ff:fe37:d8b9/64 Escopo:Link 
    92           UP BROADCAST RUNNING MULTICAST  MTU:1500  Métrica:1 
    93           pacotes RX:184453 erros:75 descartados:0 excesso:0 quadro:0 
    94           Pacotes TX:255573 erros:0 descartados:0 excesso:0 portadora:0 
    95           colisões:0 txqueuelen:1000 
    96           RX bytes:23372490 (22.2 MiB) TX bytes:136539269 (130.2 MiB) 
    97           IRQ:217 Endereço de E/S:0x6000 
    98 }}} 
    99  
    100 Note that br0 is the interface that gets the IP. The eth0 is like a "dummy" 
    101 interface. 
    102  
    103 = 3. Giving the needed access = 
    104  
    105 Ok, now we need to give some permissions to devices and files. Note that, as 
    106 everything involving permissions, there is always some risk involved on it. But 
    107 hey, its for a good cause! 
    108  
    109 = 3.1 /dev/net/tun = 
    110  
    111 First things first, to allow VBox to automatically create the virtual interface 
    112 it needs to have write access to /dev/net/tun. The best way I thought of doing it (without doing a chmod 666), was to change the ownership of the device to the vboxusers group. Since everybody that will run VBox will already be part of that group, this looked like a good solution. After that we need to give write 
    113 permissions to the members of the group. Following are the commands: 
    114  
    115 {{{ 
    116 sudo chown root.vboxusers /dev/net/tun 
    117 sudo chmod g+rw /dev/net/tun 
    118 }}} 
    119  
    120 = 3.2 ifconfig and brctl = 
    121  
    122 Besides that you (optionally) need to setuid in the "ifconfig" and "brtcl" 
    123 commands. Setuid is necessary on these commands because you need to call them on the script used to configure your network, but they both need to be run as root to do what we want. 
    124  
    125 People concerned with this security (like me) would raise an eyebrow with this, 
    126 since setuids always introduce some risk on the system. In my case I decided the risk was low, and decided to live with it.  
    127  
    128 But if you don't want to use setuid below I will show a way to make the bridging work without needing to do setuids (but having to put root password every time you boot/shutdown a VM). 
    129  
    130 So, to do the setuid run the following commands: 
    131  
    132 {{{ 
    133 chmod +s /sbin/ifconfig 
    134 chmod +s /usr/sbin/brctl 
    135 }}} 
    136  
    137 = 4. The scripts = 
    138  
    139 Now that everything is in place lets configure the scripts that will be called 
    140 by !VirtualBox every time a VM is turned on/off. I call these scripts tapUP and 
    141 tapDown, but you can name them whatever you want. The commands i use are the 
    142 same as described in the !VirtualBox User Manual, with the exception that i don't use 
    143 sudo (since i did a setuid in ifconfig and brctl). 
    144  
    145 TapUP: 
    146 {{{ 
    147 #!/bin/sh 
    148 /sbin/ifconfig $2 up  
    149 /usr/sbin/brctl addif br0 $2 
    150 }}} 
    151  
    152 !TapDown: 
    153 {{{ 
    154 #!/bin/sh 
    155 /usr/sbin/brctl delif br0 $2 
    156 }}} 
    157  
    158 If you decided to not do the setuid in step 3.2, you can use kdesu (for 
    159 example), to ask root password when running these commands. The files would look something like this: 
    160  
    161 TapUP: 
    162 {{{ 
    163 #!/bin/sh 
    164 kdesu "/sbin/ifconfig $2 up && /usr/sbin/brctl addif br0 $2" 
    165 }}} 
    166  
    167 !TapDown: 
    168 {{{ 
    169 #!/bin/sh 
    170 kdesu /usr/sbin/brctl delif br0 $2 
    171 }}} 
    172  
    173 I put both command between commas and use the "&&" so that it asks for the 
    174 password only once. 
    175  
    176 = 5. Wrapping it up = 
    177  
    178 Well, thats it! Quite easy huh?  Now all you need to do is create and virtual machine, go on its "Network" options, change the "Attached to" to "Host Interface", give the Interface a name (each machine should use a different interface!), and point the "Startup Application" and "Terminate Application", to your TapUP and !TapDown files. 
    179  
    180 I've tested it with a Windows guest, and everything worked like a charm. 
    181  
    182 = 6. Thanks = 
    183  
    184 = 7. Changelog = 
     5= Changelog = 
    1856 
    18670.1 -> Initial version[[BR]] 
    18780.2 -> wikified it a bit more and added the note about Ubuntu 7.04 (klaus)[[BR]] 
    188  
    189 = 8. References = 
    190  
    191 [1] http://en.wikipedia.org/wiki/Routing [[BR]] 
    192 [2] http://en.wikipedia.org/wiki/Bridging_%28networking%29 
     90.3 -> removed the main contents of the page (klaus)[[BR]] 

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