Sql_bind is an extension to BIND that allows admins to use SQL databases to read and store DNS data instead of flatfiles.
The package name changed because the extensions were rewritten to not be msql-specific. The latest API allows admins to drop in support for their own databases.
Sql_bind allows sysadmins to delegate the responsibility of updating nameserver tables by allowing non-sysadmins to modify databases used by sql_bind. For bind 4.9.x users, it also provides a means of dynamically updating your nameserver tables.
Currently, an outdated version of msql_bind is included in the contrib/ dir of the latest BIND sources. The latest versions are available here.
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You can, but it will not write changed entries to the database. There were too many issues dealing with security and validity of the SQL database to make writing to the database practical.
As sql_bind uses the same mechanism to validate a domain as stock BIND does, you will need to have a SOA record per zone.
You can only have on SOA record per zone. Did you run read_dnswalk twice? If so, then you have duplicates of every entry in your zone not just the SOA records. You need to clean out your database tables and rerun read_dnswalk.
If you are porting sql_bind to a new database, make sure that your "select" statment in sql_load() is correct. If your database supports the use of parentheses in a where clause, please use them.
Yes. Sql_bind only changes the user interface to BIND. With the exception of dynamic dns support in 4.9.x, sql_bind does not change the functionality of BIND.
Msql_bind was originally designed to only read certain records from a database. It was then later expanded to read every standard RR from a database. You can insert the line from sql.dom into your regular zone db files and only put the entries you want handled by sql_bind into your database. You will not need additional SOA/NS RRs if you do this.
You should first check this list to see if your problem is described here. Then the msql_bind mailing list is your best bet.