lfs-book-zh_CN/bootscripts/lfs/sbin/ifup.8

ifup(8)                                                   ifup(8)

NAME
       ifup - bring a network interface up
       ifdown - take a network interface down

SYNOPSIS
       ifup  IFACE
       ifup -h|--help
       ifup -V|--version

       ifdown IFACE
       ifdown -h|--help
       ifdown -V|--version

DESCRIPTION
       The  ifup  and  ifdown  commands  may be used to configure 
       (or, respectively, deconfigure) a network interface based 
       on interface  definitions in the file 
       /etc/sysconfig/ifconfig.IFACE.

OPTIONS
       A summary of options is included below.

       -h, --help
              Show summary of options.

       -V, --version
              Show version information.

EXAMPLES
       ifup eth0
              Bring up the interface defined in the file 
              /etc/sysconfig/ifconfig.eth0

                ONBOOT=no
                IFACE=eth0
                SERVICE=ipv4-static
                IP=192.168.1.22
                GATEWAY=192.168.1.1
                PREFIX=24
                BROADCAST=192.168.1.255

       ifdown eth0:2
              Bring down the interface defined in the file
              /etc/sysconfig/ifconfig.eth0:2

                ONBOOT=no
                IFACE=eth0
                LABEL=eth0:2
                SERVICE=dhcpcd
         
                DHCP_START="--waitip"
                DHCP_STOP="-k"
         
                # Set PRINTIP="yes" to have the script print the DHCP IP address
                PRINTIP="yes"
         
                # Set PRINTALL="yes" to print the DHCP assigned values for
                # IP, SM, DG, and 1st NS. 
                PRINTALL="no"

       ifup br0
              Bring up the interface defined in the file 
              /etc/sysconfig/ifconfig.br0
                    
                ONBOOT=yes
                IFACE=br0
                SERVICE="bridge ipv4-static"
                IP=192.168.1.22
                GATEWAY=192.168.1.1
                PREFIX=24
                BROADCAST=192.168.1.255
                STP=no                      # Spanning tree protocol, default no
                INTERFACE_COMPONENTS=eth0   # Add to IFACE
                IP_FORWARD=true

NOTES
       The program does not configure network interfaces direct-
       ly.  It runs scripts defined by the SERVICE variable in 
       the network configuration file.

       The configuration files must have the following environ-
       ment variables set:

       IFACE   - The interface to configure, e.g. eth0.  It must 
                 be available in /sys/class/net.

       SERVICE - The service script to run to bring up the inter-
                 face.  Standard services are ipv4-static and 
                 ipv4-static-route.  Other services such as dhcp
                 or bridge may be installed.  This value may
                 be a list of services when the interface is a
                 compound device such as a bridge.

       ONBOOT  - If set to 'yes', the specified interface is 
                 configured by the netowrk boot script.

       GATEWAY - The default IP address to use for routing if
                 the destination IP address is not in a static 
                 route or on a local network, e.g., 192.168.1.1.  
                 For secondary IP addresses on an interface, this 
                 parameter should not be specified.  If the service
                 is ipv4-static-route, this parameter must NOT
                 be set.

       STATIC_GATEWAY - The default IP address to use for routing
                 when setting a static routing address.  

       INTERFACE_COMPONENTS - A list of component interfaces
                 only needed for a compound device such as a bridge.  
                 This list is normally a single value, e.g. eth0, 
                 for use with a virtual host such as kvm.

       Other paramters that are service specific include:

       ipv4-static

         IP        - The IP address of the interface, 
                     e.g. 192.168.1.2.

         PREFIX    - The number of bits that specify the network
                     number of the interface.  The default, if not
                     specified, is 24.
       
         LABEL     - The label to be assigned to the interface.  
                     This is normally specified for assigning
                     additional IP addresses to a network
                     device.  Example: eth0:2 (optional)
       
         BROADCAST - The brodcast address for this interface, 
                     e.g 192.168.1.255.  If not specified, 
                     the broadcast address will be calculated
                     from the IP and PREFIX.

       ipv4-static-route

         TYPE    -  The type of route, typically 'default', 
                    'network', 'or host'.

         IP      -  The IP address for a network or host, if the
                    TYPE is not 'default'.

         PREFIX  -  The prefix for the associated IP address.

         STATIC_GATEWAY - The IP address for a network route.

         SOURCE  -  The source IP address to prefer when sending 
                    to the destinations covered by the specified
                    route. (optional)

       dhcp/dhclient

         DHCP_START - Optional parameters to pass to the dhcp client
                      at startup.

         DHCP_STOP  - Optional paremeters to pass to the dhcp client 
                      at shutdown.

         PRINTIP    - Flag to print the dhcp address to stdout

         PRINTALL   - Flag to print all obtained dhcp data to stdout

       bridge

         IP_FORWARD - An optional flag to enable the system to forward
                      inbound IP packets received by one interface to 
                      another outbound interface.  

         STP        - Set bridge spanning tree protocol.  Default is no.

FILES
       /etc/sysconfig/ifconfig.*
              definitions of network interfaces 

AUTHORS
       The ifup/ifdown suite was written by Nathan Coulson
       <nathan@linuxfromscratch.org> and Kevin P. Fleming 
       <kpfleming@linuxfromscratch.org>
       and updated by Bruce Dubbs <bdubbs@linuxfromscratch>.

SEE ALSO
       ip(8).

IFUP/IFDOWN                   8 February 2015                    ifup(8)