Handbook:Parts/Installation/Networking/ja

ネットワークの自動検出
Maybe it just works?

If the system is plugged into an Ethernet network with a DHCP server, it is very likely that the networking configuration has already been set up automatically. If so, then the many included network-aware commands on the installation CD such as, , , , , and , among others, will work immediately.

If networking has been configured, the command should list some network interfaces besides lo, such as :

The interface name on the system can be quite different from. Recent installation media might show regular network interfaces names like, , or. Just seek the interface in the output that has an IP address related to the local network.

In the remainder of this document, we will assume that the interface is called.

Optional: Configure any proxies
If the Internet is accessed through a proxy, then it is necessary to set up proxy information during the installation. It is very easy to define a proxy: just define a variable which contains the proxy server information.

In most cases, it is sufficient to define the variables using the server hostname. As an example, we assume the proxy is called proxy.gentoo.org and the port is 8080.

To set up an HTTP proxy (for HTTP and HTTPS traffic):

To set up an FTP proxy:

To set up an RSYNC proxy:

If the proxy requires a username and password, use the following syntax for the variable:

Testing the network
Try pinging your ISP's DNS server (found in ) and a web site of choice. This ensures that the network is functioning properly and that the network packets are reaching the net, DNS name resolution is working correctly, etc.

If this all works, then the remainder of this chapter can be skipped to jump right to the next step of the installation instructions (Preparing the disks).

Automatic network configuration
If the network doesn't work immediately, some installation media allow the user to use (for regular or wireless networks),  (for ADSL users) or  (for PPTP users).

If the installation medium does not contain any of these tools, continue with the Manual network configuration.


 * Regular Ethernet users should continue with Default: Using net-setup
 * ADSL users should continue with Alternative: Using PPP
 * PPTP users should continue with Alternative: Using PPTP

Default: Using net-setup
The simplest way to set up networking if it didn't get configured automatically is to run the script:

will ask some questions about the network environment. When all is done, the network connection should work. Test the network connection as stated before. If the tests are positive, congratulations! Skip the rest of this section and continue with Preparing the disks.

If the network still doesn't work, continue with Manual network configuration.

Alternative: Using PPP
Assuming PPPoE is needed to connect to the Internet, the installation CD (any version) has made things easier by including ppp. Use the provided script to configure the connection. During the setup the Ethernet device that is connected to your ADSL modem, the username and password, the IPs of the DNS servers and if a basic firewall is needed or not will be asked.

If something goes wrong, double-check that the username and password are correct by looking at or  and make sure to use the right Ethernet device. If the Ethernet device does not exist, the appropriate network modules need to be loaded. In that case continue with Manual network configuration as it will explain how to load the appropriate network modules there.

If everything worked, continue with Preparing the disks.

Alternative: Using PPTP
If PPTP support is needed, use which is provided by the installation CDs. But first make sure that the configuration is correct. Edit or  so it contains the correct username/password combination:

Then adjust if necessary:

When all that is done, run (along with the options that couldn't be set in ) to connect the server:

Now continue with Preparing the disks.

Loading the appropriate network modules
When the Installation CD boots, it tries to detect all the hardware devices and loads the appropriate kernel modules (drivers) to support the hardware. In the vast majority of cases, it does a very good job. However, in some cases, it may not auto-load the kernel modules needed.

If or  failed, then it is possible that the network card wasn't found immediately. This means users may have to load the appropriate kernel modules manually.

To find out what kernel modules are provided for networking, use the command:

If a driver is found for the network device, use to load the kernel module. For instance, to load the module:

To check if the network card is now detected, use. A detected network card would result in something like this (again, here is just an example):

If however the following error is shown, the network card is not detected:

The available network interface names on the system can be listed through the file system:

In the above example, 6 interfaces are found. The one is most likely the (wired) Ethernet adapter whereas wlan0 is the wireless one.

Assuming that the network card is now detected, retry or  again (which should work now), but for the hardcore people we explain how to configure the network manually as well.

Select one of the following sections based on your network setup:


 * Using DHCP for automatic IP retrieval
 * Preparing for wireless access if a wireless network is used
 * Understanding network terminology explains the basics about networking
 * Using ifconfig and route explains how to set up networking manually

Using DHCP
DHCP (Dynamic Host Configuration Protocol) makes it possible to automatically receive networking information (IP address, netmask, broadcast address, gateway, nameservers etc.). This only works if a DHCP server is in the network (or if the ISP provider provides a DHCP service). To have a network interface receive this information automatically, use :

Some network administrators require that the hostname and domainname provided by the DHCP server is used by the system. In that case, use:

If this works (try pinging some Internet server, like Google), then everything is set and ready to continue. Skip the rest of this section and continue with Preparing the disks.

Preparing for wireless access
When using a wireless (802.11) card, the wireless settings need to be configured before going any further. To see the current wireless settings on the card, one can use. Running might show something like:

For most users, there are only two settings that might be important to change, the ESSID (aka wireless network name) or the WEP key. If the ESSID and Access Point address listed are already those of the environment's access point and the environment is not not using WEP, then the wireless configuration is already working.

To change the ESSID, or add a WEP key, issue the following commands.


 * To set the network name to GentooNode:




 * To set a hex WEP key:




 * To set an ASCII WEP key, prefix the key with :



Confirm the wireless settings again by using. Once wireless is working,continue configuring the IP level networking options as described in the next section (Understanding network terminology) or use the tool as described previously.

Understanding network terminology
If all of the above fails, the network will need to be configured manually. This is not difficult at all. However, some knowledge of network terminology and basic concepts might be necessary. After reading this section, users will know what a gateway is, what a netmask serves for, how a broadcast address is formed and why systems need nameservers.

In a network, hosts are identified by their IP address (Internet Protocol address). Such an address is perceived as a combination of four numbers between 0 and 255. Well, at least when using IPv4 (IP version 4). In reality, such an IPv4 address consists of 32 bits (ones and zeros). Let's view an example:

Such an IP address is unique to a host as far as all accessible networks are concerned (i.e. every host that one wants to be able to reach must have a unique IP address). In order to distinguish between hosts inside and outside a network, the IP address is divided in two parts: the network part and the host part.

The separation is written down with the netmask, a collection of ones followed by a collection of zeros. The part of the IP that can be mapped on the ones is the network-part, the other one is the host-part. As usual, the netmask can be written down as an IP address.

In other words, 192.168.0.14 is part of the example network, but 192.168.1.2 is not.

The broadcast address is an IP address with the same network-part as the network, but with only ones as host-part. Every host on the network listens to this IP address. It is truly meant for broadcasting packets.

To be able to surf on the Internet, each computer in the network must know which host shares the Internet connection. This host is called the gateway. Since it is a regular host, it has a regular IP address (for instance 192.168.0.1).

Previously we stated that every host has its own IP address. To be able to reach this host by a name (instead of an IP address) we need a service that translates a name (such as dev.gentoo.org) to an IP address (such as 64.5.62.82). Such a service is called a name service. To use such a service, the necessary name servers need to be defined in.

In some cases, the gateway also serves as a nameserver. Otherwise the nameservers provided by the ISP need to be entered in this file.

To summarize, the following information is needed before continuing:

Using ifconfig and route
Setting up the network consists of three steps:


 * 1) Assign an IP address using
 * 2) Set up routing to the gateway using
 * 3) Finish up by placing the nameserver IPs in

To assign an IP address, the IP address, broadcast address and netmask are needed. Then execute the following command, substituting ${IP_ADDR} with the right IP address, ${BROADCAST} with the right broadcast address and ${NETMASK} with the right netmask:

Set up routing using. Substitute ${GATEWAY} with the right gateway IP address:

Now open :

Fill in the nameserver(s) using the following as a template. Make sure to substitute ${NAMESERVER1} and ${NAMESERVER2} with the appropriate nameserver addresses:

That's it. Now test the network by pinging some Internet server (like Google). If this works, congratulations then. Continue with Preparing the disks.