Day
Light Saving Change in USA -
Summary of changes with links to patches and information. -
Application
Monitoring - Challenges
, best practices and implementation of application monitoring is
discussed.
- Unix
Commands - A
quick reference to commonly used unix commands .
- Solaris
Network Configuartion -
Simplified
: Quick reference to setting up network in Solaris
system
- Performance
Monitoring - iostat , vmstat & netstat -
Introduction to
performance monitoring tools with example and
command syntax.
- crontab
in Unix
- A Quick
Reference to setting up and using cron jobs in unix
.
- Veritas
Volume Manager-1:
- Using vxdiskadm to
add & manage disks & disk groups
.
- Veritas
Volume Manager-2:
- Using vxassist to
create ,configure & manage volumes .
- Admin's
Guide to Solstice Disk Suite:
Complete practical reference including root
mirroring and trouble shooting.
- Securing
Solaris :
- A few suggestions to
make your Solaris system secure from internal and
external intrusion.
-
- Solaris
Installation
- Step by step guide
to Solaris Installation.
- Jumpstart
Server
- Network
installation of Solaris over one or multiple
systems.
- Booting
Process
- Details of Solaris
booting process.
- Booting
Problems in Solaris
- Common booting
related error messages and their possible solution
- DNS
Server
- Setting up DNS
server
- Trouble
Shooting DNS Some
of the configuration and nslookup related errors
explained.
- NIS+
- Server , Clients
setup and commands.
- OpenBoot
Parameters
- Reference table of
important parameters and their values.
- Solaris
Error Messages
- Alphabetical listing
of common Solaris Error Messages and their explanation
- Checking
& Repairing File systems with fsck
fsck
operation ,syntax and explanation of some common
error messages
- Vi
Quick Reference
- vi basics for
reference
- explanations.
-
- Open Directory
- Unix
, Solaris
Administration
- Sun.com
- BigAdmin
-
-
-
- FAQs
- unix
, unix
programming , VI
,Sendmail ,
Bind
- ssh
,BASH
,Security,
Secure
unix programming,
Unix socket
- SCSI
- Solaris
2 ,
Solaris
x86 ,NIS+ FreeBSD
,RedHat
, HPUX
- :
- Unix
- Unix
History and timeline ,
- Overview
of the UNIX
- Microsoft
Windows NT Server 4.0 versus UNIX
- Overview
of Unix Commands
- Unix
for advance Users ,
- Unix
Bourne Shell Guide with Ksh ,
- Korn
Shell
- BASH
reference Guide,
- :
- Solaris
Documentation
- Solaris
7 System Administration Collection
- Solaris
8 System Administrator Collection
- Solaris
9 System Administartion Collection
- Creating
Solaris Packages
- Multibooting
Solaris
- :
- Sun
- Sun
System Handbook
- Sun
Hardware Info.
- :
- Documentation
Home
- Sun
, BSD ,Linux
,Hp,Veritas
- :
- Patches &
Softwares
- Solaris
Patches ,
- Solaris
Freeware ,
- GNU
Software,
- big
brother ,
- webmin
.com ,
- bugzilla.org
- :
- Certification
Info
- Sun
,Red
Hat , HP
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DNS TroubleShooting
DNS troubleshooting , this article
describes some of the common dns problems . The article describes in
its first phase the dns errors relating to configuration errors
which are related to dns server setup and its basic functionality . Second
phase talks about the nslookup related errors when the dns servers seems
to be working corretcly but names resolution fail .
- A. Configuration problems
-
- 1) named
fail to start
- 2) Trailing
dots
- 3) Serial
No. & Refresh Time
- 4) Cname
-
- B. nslookup related errors
-
- 1) No
response from server.
- 2) No
Record is available.
- 3) No
Information.
- 4) Unspecified
Error
- 5) Query
Refused
-
Configuration problems
- 1. name server daemon - named fail to
start .
- This happens generally when the
syntax in the configuration file is not correct . the named daemon will try to
read named.conf file and if comes across any error it will abort and come out
without starting named.
- start the named in debug mode and look the output in
the debug file - default is named.run .There are different debug level which can
be used depending upon the nature of problem.
- It is always better to double check the
configuration files for syntax etc. to avoid problems later on.
-
- 2.Trailing dots :
- Current domain name is automatically appended to the
entries in the master data file .This might be correct for a entry like www to
be read as www.yourdomain.com but it
will be incorrect if www.yourdomain.com
entry is read as www.yourdomain.com.yourdomain.com
.So to avoid appending domain name a trailing dot is put on such names .
-
- 3. Serial No & Refresh time :
- Serial no must be incremented after a change is made
to zone file of a master server . The serial no. is checked by the
secondary dns server After refresh time is over and transfer of zone files takes place if serial no
is incremented. Refresh time depends on the frequency of changes made to dns
servers data and is in seconds.
4. CNAME
- A CNAME record is not allowed to coexist
with any other data record. The DNS server finds the cname entry &
it ignores other entries .In the example below NS entries are ignored
.
- dnsserver
IN NS ns1
-
IN NS ns2
-
IN CNAME dnsmain
- dnsmain
IN A 10.20.30.40
-
- correct representation would be :-
- dnsserver
IN NS ns1
-
IN NS ns2
-
IN A 10.20.30.40
- dnsmain
IN A 10.20.30.40
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nslookup related errors
nslookup is very important troubleshooting
tool & following are some of the most common problems :
- 1.No Response from Server :
- If nslookup gives this response even for
the local host name then it is possible that DNS server itself is not
running .Check the named process and restart it in debug mode for clues
about the problems .
2.No record available :This
indicates that the default records types are not available in the target dns
server. A better way would be to look for all type of records by mentioning
"set type=any" in nslookup.
- 3.No information
: nslookup did tried to find a host of the specified name but the name
server did not have any information about that in its data files .
- Check spellings & trailing dots in
data files of DNS server.
4.Unspecified error
:This is mainly caused when number of NS records exceeds the capacity of
datagram packet so don't put too many NS records for a domain.
5.Query Refused :
This can be caused due to security relatd options in configuration file .Make
sure the network of nslookup host is mentioned in allow-transfer statement and
also the address 127.0.0.1 if nslookup is being run on name server as
host.
- Next
Steps
This article tried to cover a
domain name server related problems . DNS subject is very vast and not everything can
be covered in a article . If you wish to learn more about DNS there are some good books available for online buying from
Amazon.com . You should have following two books in your bookshelf if
you are going to setup and maintain the DNS servers under unix environment.
DNS
and BIND, Fourth Edition (Paperback) by
Paul
Albitz, Cricket
Liu
DNS
& BIND Cookbook by
Cricket
Liu
The amazon display panel below shows
some of the best-selling books for DNS and you can choose the book here or
visit my other website besttechbooks.com
for more books on domain name service from Amazon.com.
You can show your appreciation by buying the books for yourself and
encouraging the friends to buy using amazon links below or
anywhere at adminschoice.com
or besttechbooks.com
. Thanks for your appreciation in advance.
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