30.8. Editing a Slave Zone
After a slave zone has been created, it is still possible to edit several options that apply to it. Naturally there is no way to add or edit the actual records within the zone, but you can still change the list of master servers, the records file and the clients that allowed to query it. To change these setting, the steps to follow are:
1. | On the module's main page, click on the icon for the slave zone that you want to edit. Your browser will display the form shown in Figure 30.6. Figure 30.6. The slave zone editing form.
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2. | Scroll down to the Zone Options form at the bottom of the page. |
3. | To edit the list of other master and slave servers for this zone, change the IP addresses in the Master servers field. If a new secondary server has been added, it should be added to this list on all other secondaries so that they can do zone transfers from it. If the IP address of the master has changed, the list must be updated with the new address. |
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5. | If the Records file field is set to None, records transferred from the master server for this zone will be kept in memory only. However if a filename is entered, records will be written to that file instead in the standard format. This is the best option, as it minimizes zone transfers and allows you to view the records on the secondary server, as explained below. |
6. | To have this DNS server notify others when the zone changes, change the Notify slaves of changes? field to Yes. This is only really useful if there are other secondary servers that perform zone transfers from this one, and may not be able to receive update notifications from the master server. The DNS servers to notify are determined from the Name Server records for the zone, and the contents of the Also notify slaves field. |
7. | By default, all DNS clients and servers will be able to lookup records in the zone. To change this, fill in the Allow queries from field with a list of IP addresses, IP networks and BIND ACL names. If the field is left empty, the field with the same name on the global Zone Defaults page determines which clients are allowed. |
8. | To restrict the clients and servers that are allowed to perform zone transfers of all the records in this domain, fill in the Allow transfers from field with a list of IP addresses, IP networks and ACL names. If it is left empty, the Allow transfers from field on the Zone Defaults page applies instead. |
9. | The other fields on the form such as Check names? and Allow updates from? are not really used for slave zones, and so can be left unchanged. |
10. | When you are done making changes, click the Save button. As long as there were no syntax errors in your input, you will be returned to the module's main page. Click the Apply Changes button there to make the modifications active. Note that this will not always force a re-transfer of the zone, even if the master servers have changed. For slave zones that use records files, BIND will only do a transfer when the zone expires or the server receives notification of a change. |
When editing a slave zones that uses a records file, it is possible to browse the records in Webmin. At the top of the page that appears when you click on the slave zone's icon is a table of record types, just like the one that appears on the master zone form. Each can be clicked on to list the names and values of records of that type in the zone, as known to the secondary server. Editing or adding to them is impossible of course, as any changes must be made on the master server which is the authoritative source of records for the domain.
To stop your system acting as a slave server for a zone, you will need to delete it from the BIND configuration. This is generally a safe procedure, as the all the records in the zone have been copied from a master server and can be easily replaced. However, you should update the Name Server records in the zone and notify the parent domain's registrar that you system is no longer a secondary for the zone, so that other DNS servers do not waste time querying it.
To delete a slave zone, the steps to follow are:
1. | On the module's main page, click on the icon for the slave zone that you want to edit. This will take you to the form shown in Figure 30.6. |
2. | Click on the Delete button in the bottom right-hand corner of the page, which will display a confirmation form. |
3. | Hit the Delete button if you are sure you want to delete the zone. |
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5. | On the master server, remove the Name Server (NS) record for this secondary server from the zone. |
6. | If this is an Internet domain, notify the parent zone registrar of the removal of this secondary server. Failure to do so could cause problems if other DNS servers attempt to query this one for records in the domain when it cannot provide answers. |
The final thing that you can do to a slave zone is convert it to a master. This is only possible for zones that use a records file, so that Webmin can view and edit that file in future. If you do such a conversion, make sure that the original master server is changed to become a slave or stops hosting the zone altogether—the same domain cannot be served by two masters.
The steps to convert a zone are:
1. | Click on its icon on the module's main page. |
2. | Scroll down to the bottom of the slave zone page and hit the Convert to master zone button. This will immediately update the named.conf file to change the zone's type, but will not make any other changes. |
3. | To make the conversion active, click on the Apply Changes button on the module's main page. |
4. | You can now edit records in the domain just as you would with any normal master zone, by following the instructions in Section 30.4 “Adding and Editing Records”. |