What does ndd do?

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What does ndd do? ..

Answer / mahipal

The ndd Command
Several of the network settings discussed in this article
are configured using the ndd command. It is used to examine
and set kernel module parameters, namely the Transmission
Control Protocol/Internet Protocol (TCP/IP) drivers. Most
kernel parameters accessible through ndd can be modified
without rebooting the system. To see which parameters are
available, use the following ndd commands:

# ndd /dev/arp \?
# ndd /dev/icmp \?
# ndd /dev/ip \?
# ndd /dev/tcp \?
# ndd /dev/udp \?These commands list the parameters for the
Address Resolution Protocol (ARP), Internet Control Message
Protocol (ICMP), IP, TCP, and User Datagram Protocol (UDP)
drivers. In this updated BluePrint OnLine article, the
various drivers are listed in alphabetic order.

The Solaris 8 and 9 OE releases include support for the
next version of the Internet Protocol suite (IPv6) and the
Internet Protocol Security architecture (IPsec). These have
additional drivers. A list of parameters for these drivers
can be found with the following commands:

# ndd /dev/ip6 \?
# ndd /dev/icmp6 \?
# ndd /dev/tcp6 \?
# ndd /dev/udp6 \?
# ndd /dev/ipsecesp \?
# ndd /dev/ipsecah \?The IPv6 parameters for the ICMP, IP,
TCP, and UDP drivers are also listed in the standard (IPv4)
parameter lists. This article does not discuss IPsec, but
the parameters are listed here for completeness. Neither
IPv6 nor IPsec support will be supported in any Solaris OE
release earlier than Solaris 8 OE.

There are also network interface device drivers with
parameters that can be adjusted using the ndd command. The
following command will list the parameters for the hme
(FastEthernet) device driver:

# ndd /dev/hme \?The "\?" string is required to prevent the
shell from interpreting the "?" as a special character.
Using "\?" will list all parameters for the driver and
indicate whether the parameter is read only, write only, or
read and write. The current parameter value or status
information can be read by specifying the driver and
parameter names.

This example shows the output of a ndd command examining
the debugging status of the ARP driver. (The output "0"
indicates that the option is disabled.)

# ndd /dev/arp arp_debug
0ndd-specified parameter values are integers with "0"
meaning disable, "1" meaning enable, or a large integer to
set a time or size value. Setting parameters requires the "-
set" option, the driver name, the parameter name, and the
new value. For example, to enable debugging mode in the ARP
driver use this ndd command:

# ndd -set /dev/arp arp_debug 1Notes on Parameter Changes
Previously, only some ndd parameter documentation was
available from Sun. This has been a known problem. Since
the release of the Solaris 8 OE, there is now documentation
of selected tunable TCP/IP parameters. The book is the
Solaris Tunable Parameters Reference Manual and is
available on the docs.sun.comSM web site. Most of the
parameter information for the Solaris 9 OE is also
applicable to previous releases.

Network parameters set with the ndd command apply to the
currently running Solaris instance; parameter changes do
not last past system reboots. Once a system is booted, the
default parameters will be used. To provide a simple method
of setting the ndd network parameters mentioned in this
article at Solaris boot time, a system init script has been
created and is described in "Sample System nddconfig init
Script."

Setting driver parameters involves making trade-offs. Most
parameters involve changing the default Solaris OE
configuration. The default settings are optimal for most
situations. Adjusting parameters might affect normal system
operation, so Sun does not encourage parameter changes.

All ndd parameter changes suggested in this article include
a discussion of trade-offs, where appropriate. Some
settings change the expected operation of systems; these
are noted. Most of these recommended parameter changes are
being actively used on production systems at customer
sites.

Sun sometimes alters parameter names or adds additional
parameters between releases of the Solaris OE. Most of the
IPv4 parameters described in this article are used
consistently across Solaris OE releases. When there are
exceptions, the text for the parameter specifically
mentions the OE differences