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Linux System Administration
book

Linux System Administration

by Tom Adelstein, Bill Lubanovic
March 2007
Intermediate to advanced content levelIntermediate to advanced
304 pages
11h 12m
English
O'Reilly Media, Inc.
Content preview from Linux System Administration
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Appendix: bash Script Samples
Don’t try to execute this command at your terminal and view the
results on the screen. You’ll go blind for 10 minutes and your dog will
start meowing. Did you give in to the temptation to do so? You may
have to execute an stty sane command to restore the screen to a useful
state.
Authoritative DNS Lookup
This script uses the dig command introduced in Chapter 3 to do DNS lookups,
bypassing the cache of the local DNS caching server. One feature of this script is that
it uses its own name to specify what DNS record type to look up. If the script is
named a, it looks up DNS
A records. If it is named soa, it looks up DNS SOA records.
The name ptr is a special case that takes an IPv4 address and converts it to the proper
in-addr.arpa form to do the actual lookup. You should make a copy of this script
with the appropriate name for each of the common DNS record types you may need
to look up: a, aaaa, mx, and so on. You can also use hard links or symlinks to create
the aliases.
Regardless of the name, the script takes a list of hostnames to look up as arguments:
#!/bin/bash
#----------------------------------------------------------------
# Copyright © 2006 - Philip Howard - All rights reserved
#
# script a, aaaa, cname, mx, ns, ptr, soa, txt
#
# purpose Perform direct DNS lookups for authoritative DNS
# data. This lookup bypasses the local DNS cache
# server.
#
# syntax a [ ...
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Publisher Resources

ISBN: 9780596009526Supplemental ContentCatalog PageErrata