Monday, April 15, 2013

What is a Glue Record?

Category: — SkyHi @ Monday, April 15, 2013

Glue Records

This article offers a definition of a Glue Record, a description of why a Glue Record is need and how they are resolved through DNS, and how to create a Glue Record through the CloudAccess.net Client Area.

What is a Glue Record?

Why are Glue Records needed?

How to create a Glue Record

What is a Glue Record?

A Glue Record is the IP Address of a name server at a domain name registry. Glue Records are fundamental parts of DNS records because they help to resove DNS servers at a core level. If you would like to change the name servers for a site, you ll have to provide the Glue Records for the new name serves. Without them, a domain name will not work because anyone requiring the DNS information will be stuck in a loop. There is a cyclic dependency of circular referencing. Circular references exist where the name servers for a domain can t be resolved without resolving the domain they re responsible for. Glue Records are additional A records that allow the DNS client to locate name servers. 

When are Glue Records needed?

For example, let s say your domain (yourdomain.com) is using ns1.nameserver.com and ns2.nameserver.com as name servers, but gridfast.net also uses ns1.nameserver.com and ns2.nameserver.com as name servers. This is how the cyclic dependency is created. To break the cycle, DNS systems use Glue Records. 
You can also understand Glue Records by understanding A Records. An A record (an A address) is a DNS record that can be used to point your domain name and host names to a static IP address. For example, the A record for gridfast.net includes ns1.gridfast.net and ns2.gridfast.net and their IP addresses. These servers can be reached directly without any further resolution. For a domain name like CloudAccess.net, however, the root DNS servers pass the ns1.gridfast.net and ns2.gridfast.net nameservers, and a further chain of resolution is needed to resolve the DNS. This is when a Glue Record is needed.


REFERENCES
http://www.cloudaccess.net/infrastructure-networking/66-servers-dns/318-glue-records.html

MySQL 4.1+ using old authentication

Category: — SkyHi @ Monday, April 15, 2013

When I was working with XAMPP in Ubuntu and asked write PHP script to connect to remote MySQL server which is using PASSWORD hash function to save the password for user, and I found following error.

Warning: mysql_connect() [function.mysql-connect]: Premature end of data (mysqlnd_wireprotocol.c:554) in path/to/the/file/where/connection/script/is/written/

Warning: mysql_connect() [function.mysql-connect]: OK packet 1 bytes shorter than expected in path/to/the/file/where/connection/script/is/written/

Warning: mysql_connect() [function.mysql-connect]: mysqlnd cannot connect to MySQL 4.1+ using the old insecure authentication. Please use an administration tool to reset your password with the command SET PASSWORD = PASSWORD('your_existing_password'). This will store a new, and more secure, hash value in mysql.user. If this user is used in other scripts executed by PHP 5.2 or earlier you might need to remove the old-passwords flag from your my.cnf file in path/to/the/file/where/connection/script/is/written/

As you will see, the core issue here is that MySQL can have passwords with hashes stored in the old 16-character format, which is not supported by PHP 5.3′s new mysqlnd library.
Since I couldn’t find a good solution with a quick Google, here is how I solved this without having to downgrade PHP or MySQL (as some of the solutions suggested):

1. Change MySQL to NOT to use old_passwords
It seems that even MySQL 5.x versions still default to the old password hashes. You need to change this in “my.cnf” (e.g. /etc/my.cnf): remove or comment out the line that says
old_passwords = 1
Restart MySQL. If you don’t, MySQL will keep using the old password format, which will mean that you cannot upgrade the passwords using the builtin PASSWORD() hashing function. You can test this by running:
 
mysql> SELECT Length(PASSWORD('xyz'));
+-------------------------+
| Length(PASSWORD('xyz')) |
+-------------------------+
|                      16 |
+-------------------------+
1 row in set (0.00 sec)
The old password hashes are 16 characters, the new ones are 41 characters.
2. Change the format of all the passwords in the database to the new format
Connect to the database, and run the following query:
mysql> SELECT user,  Length(`Password`) FROM `mysql`.`user`;

This will show you which passwords are in the old format, ex:
+----------+--------------------+
| user     | Length(`Password`) |
+----------+--------------------+
| root     |                 41 |
| root     |                 16 |
| user2    |                 16 |
| user2    |                 16 |
+----------+--------------------+
Notice here that each user can have multiple rows (one for each different host specification).
To update the password for each user, run the following:
UPDATE mysql.user SET Password = PASSWORD('password') WHERE user = 'username';
Finally, flush privileges:
FLUSH PRIVILEGES;


REFERENCE
http://lampsailesh.blogspot.com/2011_05_01_archive.html#5294498109303285481
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