Network Configuration
if by mistak remove network and network manager in ubuntu 14.4
or by mistake use commad
apt-get auto-remove and you have not connect internet then first connect network blow step and try to solve
Ubuntu ships with a number of graphical utilities to configure your
network devices. This document is geared toward server administrators
and will focus on managing your network on the command line.
Ethernet Interfaces
Ethernet interfaces are identified by the system using the naming convention of
ethX, where X
represents a numeric value. The first Ethernet interface is typically identified
as eth0, the second as
eth1, and all others should move up in
numerical order.
Identify Ethernet Interfaces
To quickly identify all available Ethernet interfaces, you can use the
ifconfig command as shown below.
ifconfig -a | grep eth eth0 Link encap:Ethernet HWaddr 00:15:c5:4a:16:5a
Another application that can help identify all network interfaces available to your system
is the lshw command. In the example below, lshw
shows a single Ethernet interface with the logical name of eth0
along with bus information, driver details and all supported capabilities.
sudo lshw -class network *-network description: Ethernet interface product: BCM4401-B0 100Base-TX vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:03:00.0 logical name: eth0 version: 02 serial: 00:15:c5:4a:16:5a size: 10MB/s capacity: 100MB/s width: 32 bits clock: 33MHz capabilities: (snipped for brevity) configuration: (snipped for brevity) resources: irq:17 memory:ef9fe000-ef9fffff
Ethernet Interface Logical Names
Interface logical names are configured in the file
/etc/udev/rules.d/70-persistent-net.rules. If you would
like control which interface receives a particular logical name, find the line
matching the interfaces physical MAC address and modify the value of
NAME=ethX to the desired logical name.
Reboot the system to commit your changes.
Ethernet Interface Settings
ethtool is a program that displays and changes Ethernet
card settings such as auto-negotiation, port speed, duplex mode, and Wake-on-LAN. It
is not installed by default, but is available for installation in the repositories.
sudo apt install ethtool
The following is an example of how to view supported features and configured
settings of an Ethernet interface.
sudo ethtool eth0 Settings for eth0: Supported ports: [ TP ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Half 1000baseT/Full Supports auto-negotiation: Yes Advertised link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Half 1000baseT/Full Advertised auto-negotiation: Yes Speed: 1000Mb/s Duplex: Full Port: Twisted Pair PHYAD: 1 Transceiver: internal Auto-negotiation: on Supports Wake-on: g Wake-on: d Current message level: 0x000000ff (255) Link detected: yes
Changes made with the ethtool command are temporary
and will be lost after a reboot. If you would like to retain settings, simply add
the desired ethtool command to a pre-up
statement in the interface configuration file /etc/network/interfaces.
The following is an example of how the interface identified as eth0
could be permanently configured with a port speed of 1000Mb/s running in full duplex mode.
auto eth0 iface eth0 inet static pre-up /sbin/ethtool -s eth0 speed 1000 duplex full
Although the example above shows the interface configured to use the
static method, it actually works with other
methods as well, such as DHCP. The example is meant to demonstrate only proper
placement of the pre-up statement in relation
to the rest of the interface configuration.
IP Addressing
The following section describes the process of configuring your systems IP address
and default gateway needed for communicating on a local area network and the
Internet.
Temporary IP Address Assignment
For temporary network configurations, you can use standard commands
such as ip, ifconfig
and route, which are also found on most other
GNU/Linux operating systems. These commands allow you to configure settings
which take effect immediately, however they are not persistent and will
be lost after a reboot.
To temporarily configure an IP address, you can use the ifconfig
command in the following manner. Just modify the IP address and subnet mask to match your
network requirements.
sudo ifconfig eth0 10.0.0.100 netmask 255.255.255.0
To verify the IP address configuration of eth0,
you can use the ifconfig command in the following manner.
ifconfig eth0 eth0 Link encap:Ethernet HWaddr 00:15:c5:4a:16:5a inet addr:10.0.0.100 Bcast:10.0.0.255 Mask:255.255.255.0 inet6 addr: fe80::215:c5ff:fe4a:165a/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:466475604 errors:0 dropped:0 overruns:0 frame:0 TX packets:403172654 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2574778386 (2.5 GB) TX bytes:1618367329 (1.6 GB) Interrupt:16
To configure a default gateway, you can use the route
command in the following manner. Modify the default gateway address to match
your network requirements.
sudo route add default gw 10.0.0.1 eth0
To verify your default gateway configuration, you can use the route
command in the following manner.
route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.0.0 0.0.0.0 255.255.255.0 U 1 0 0 eth0 0.0.0.0 10.0.0.1 0.0.0.0 UG 0 0 0 eth0
If you require DNS for your temporary network configuration, you can add DNS server
IP addresses in the file /etc/resolv.conf. In general, editing
/etc/resolv.conf directly is not recommanded, but this is a
temporary and non-persistent configuration. The example below
shows how to enter two DNS servers to /etc/resolv.conf, which
should be changed to servers appropriate for your network. A more lengthy description
of the proper persistent way to do DNS client configuration is in a following section.
nameserver 8.8.8.8 nameserver 8.8.4.4
If you no longer need this configuration and wish to purge all IP configuration from
an interface, you can use the ip command with the flush option
as shown below.
ip addr flush eth0
Flushing the IP configuration using the ip command does not clear the
contents of /etc/resolv.conf. You must remove or modify those entries manually,
or re-boot which should also cause /etc/resolv.conf, which is actually now a
symlink to /run/resolvconf/resolv.conf, to be re-written.
Dynamic IP Address Assignment (DHCP Client)
To configure your server to use DHCP for dynamic address assignment, add the
dhcp method to the inet address family statement
for the appropriate interface in the file /etc/network/interfaces.
The example below assumes you are configuring your first Ethernet interface identified as
eth0.
auto eth0 iface eth0 inet dhcp
By adding an interface configuration as shown above, you can manually enable the
interface through the ifup command which initiates the
DHCP process via dhclient.
sudo ifup eth0
To manually disable the interface, you can use the ifdown
command, which in turn will initiate the DHCP release process and shut down the
interface.
sudo ifdown eth0
Static IP Address Assignment
To configure your system to use a static IP address assignment, add the
static method to the inet address family statement
for the appropriate interface in the file /etc/network/interfaces.
The example below assumes you are configuring your first Ethernet interface identified as
eth0. Change the address,
netmask, and gateway
values to meet the requirements of your network.
auto eth0 iface eth0 inet static address 10.0.0.100 netmask 255.255.255.0 gateway 10.0.0.1
By adding an interface configuration as shown above, you can manually enable the
interface through the ifup command.
sudo ifup eth0
To manually disable the interface, you can use the ifdown
command.
sudo ifdown eth0
Loopback Interface
The loopback interface is identified by the system as lo
and has a default IP address of 127.0.0.1. It can be viewed using the ifconfig command.
ifconfig lo 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:2718 errors:0 dropped:0 overruns:0 frame:0 TX packets:2718 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:183308 (183.3 KB) TX bytes:183308 (183.3 KB)
By default, there should be two lines in /etc/network/interfaces
responsible for automatically configuring your loopback interface. It is recommended that you
keep the default settings unless you have a specific purpose for changing them. An example of
the two default lines are shown below.
auto lo iface lo inet loopback
Name Resolution
Name resolution as it relates to IP networking is the process of mapping IP addresses
to hostnames, making it easier to identify resources on a network. The following section
will explain how to properly configure your system for name resolution using DNS and static
hostname records.
DNS Client Configuration
Traditionally, the file /etc/resolv.conf was a static configuration file that rarely
needed to be changed or automatically changed via DCHP client hooks. Nowadays, a computer can switch from
one network to another quite often and the resolvconf
framework is now being used to track
these changes and update the resolver's configuration automatically.
It acts as an intermediary between programs
that supply nameserver information and applications that need
nameserver information. Resolvconf gets populated with information
by a set of hook scripts related to network interface configuration.
The most notable difference for the
user is that any change manually done to /etc/resolv.conf will be lost as it gets overwritten each time
something triggers resolvconf. Instead, resolvconf uses DHCP client hooks, and /etc/network/interfaces to
generate a list of nameservers and domains to put in /etc/resolv.conf, which is now a symlink:
/etc/resolv.conf -> ../run/resolvconf/resolv.conf
iface eth0 inet static
address 192.168.3.3
netmask 255.255.255.0
gateway 192.168.3.1
dns-search example.com
dns-nameservers 192.168.3.45 192.168.8.10
The search option can also be used with multiple domain names
so that DNS queries will be appended in the order in which they are entered. For example, your
network may have multiple sub-domains to search; a parent domain of example.com,
and two sub-domains, sales.example.com and dev.example.com.
If you have multiple domains you wish to search, your configuration might look like the following:
iface eth0 inet static
address 192.168.3.3
netmask 255.255.255.0
gateway 192.168.3.1
dns-search example.com sales.example.com dev.example.com
dns-nameservers 192.168.3.45 192.168.8.10
If you try to ping a host with the name of server1, your system
will automatically query DNS for its Fully Qualified Domain Name (FQDN) in the following order:
-
server1.example.com
-
server1.sales.example.com
-
server1.dev.example.com
No comments:
Post a Comment