oreilly.comSafari Books Online.Conferences.

Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

Buy it now, or read it online on Safari Bookshelf.


dnssec-keygen [options] domain-name

System administration command. Generate encrypted Secure DNS (DNSSEC) or Transaction Signatures (TSIG) keys for domain-name. When the key is completed, dnssec-keygen prints the key identifier to standard output and creates public and private keyfiles whose names are based on the key identifier and the filename extensions .key and .private. It creates both files even when using an asymmetric algorithm, such as HMAC-MD5. For more information on Secure DNS, see DNS and BIND (O'Reilly), or read RFC 2535.


-a algorithm

Specify the cryptographic algorithm to use. Accepted values are RSAMD5, RSA, DSA, DH, or HMAC-MD5. DSA or RSA should be used for Secure DNS, and HMAC-MD5 for TSIG.

-b bitsize

Specify the key bitsize. Accepted values depend on the encryption algorithm used, but, in general, a larger key size means stronger encryption. 128 bits is usually considered reasonably secure, and 512 quite good.

-c class

The domain record for which the key is being generated should contain class. When this option is not given, a class of IN is assumed.


Use a large exponent when generating an RSA key.

-g generator

Specify the number to use as a generator when creating a DH (Diffie Hellman) key. Accepted values are 2 and 5.


Print a help message, then exit.

-n type

The owner of the key must be of the specified type. Accepted values are ZONE, HOST, ENTITY, or USER.

-p protocol

Specify the protocol value for the generated key. Accepted values are given in RFC 2535 and other DNS Security RFCs. By default, the value is either 2 (email) or 3 (DNSSEC).

-r device

Specify the device to use as a source of randomness when creating keys. This can be a device file, a file containing random data, or the string keyboard to specify keyboard input. By default, /dev/random will be used when available, and keyboard input will be used when it is not.

-s type

Specify whether the key can be used for authentication, confirmation, both, or neither. Accepted values for type are AUTHCONF, NOAUTHCONF, NOAUTH, or NOCONF.