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Chapter 12. Network Scripts

The two interface control scripts are

ifdown

and

ifup

and are symbolic links to scripts in the

/sbin/

directory. When either of these scripts are called, they require a value of the interface to be specified,

such as:

ifup eth0

Determining IP information for eth0... done.

At

that

point,

the

/etc/rc.d/init.d/functions

and

/etc/sysconfig/network 

scripts/network functions

files are used to perform a variety of tasks. See Section 12.4 for

more information.

After verifying that an interface has been specified and that the user executing the request is allowed

to control the interface, the correct script for the type of interface device brings the interface up or

down. The following interface control scripts are the most common:

  ifup aliases

  Configures IP aliases from interface configuration files when more than one IP

address is associated with an interface.

  ifdown cipcb

and

ifup cipcb

  Used to bring Crypto IP Encapsulation (CIPE) connections

up and down.

  ifdown ipv6

and

ifup ipv6

  Contains IPv6 related function calls using environment vari 

ables in various interface configuration files and

/etc/sysconfig/network

.

  ifup ipx

  Used to bring up an IPX interface.

  ifup plip

  Used to bring up a PLIP interface.

  ifup plusb

  Used to bring up a USB interface for network connections.

  ifdown post

and

ifup post

  Contains commands to be executed after an interface is brought

up or down.

  ifdown ppp

and

ifup ppp

  Used to bring a PPP interface up or down.

  ifup routes

  Adds static routes for a device as its interface is brought up.

  ifdown sit

and

ifup sit

  Contains function calls related to bringing up and down an IPv6

tunnel within an IPv4 connection.

  ifdown sl

and

ifup sl

  Used to bring an SLIP interface up or down.

Be aware that removing or modifying any scripts in the

/etc/sysconfig/network scripts/

directory can cause interface connections to act strangely or fail, as these scripts. Only advanced users

should modify scripts related to a network interface.

You can also use the init script

/etc/rc.d/init.d/network

to activate and deactive all network

interfaces configured to start at boot time with the command:

/sbin/service network action

Where action is either

start

,

stop

, or

restart

. You can also use the command

/sbin/service/network status

to view a list of configured devices and currently active

devices.

12.4. Network Functions

Red Hat Linux makes use of several files that contain important functions that are used in various

ways to bring interfaces up and down. Rather than forcing each interface control file to contain the

same functions as another, these functions are grouped together in a few files that can be sourced when

needed.