Adding/Editing Zone Records using Webmin

Adding and editing records

The most useful feature of the BIND DNS Server module is the ability to add, edit and delete records in the master zones hosted by your server. For example, if you wanted to set up a webserver in your domain example.com, you would need to add an Address record for www.example.com with the IP address of the server. To add a new record like this, the steps to follow are :

1. On the module’s main page, click on the icon for the zone that you want to add to. This will bring up the page shown below, at the top of which is a table of icons, one for each record type.
2. Click on the icon for the type of record that you want to add. The most common type is Address, which associates an IP address with a hostname. See the Record types section below for a complete list of all the supported record types.
3. Clicking on the icon will take you to a page listing all existing records of that type. Above the list is a form for entering a new record.
4. In the Name field, enter the name of the new record relative to the zone name. For example, if you wanted to add the record www.example.com, you should just enter www. It is also possible to enter the full record name, as long as it has a dot at the end to indicate that it is not relative to the zone. Do not enter just www.example.com, as it will be converted to www.example.com.example.com, which is probably not what you want.
5. If this record is going to change more frequently than the rest of the zone, change the Time-To-Live field from Default to the estimated time between changes. This determines how long DNS clients and other servers will cache the record for.
6. If you are adding an Address record, enter the complete IP address of the host into the Address field. See the table below for a description of the fields that appear when adding other types of records and what they mean.
7. The field Update reverse? only appears when adding an Address record. It controls the automatic creation of a corresponding record in a reverse zone which associates the hostname with the IP address. Naturally, this can only be done if the IP that you enter is in a network that your system is the primary reverse DNS server for. This keeps the forward and reverse zones synchronized, which can be very useful. If Yes is selected, a reverse address record will be added as long as one does not already exist in the reverse zone for the same IP address. Often many hostnames will have the same IP, such as those use for name-based virtual hosting. In cases like these, you don’t want to change the reverse mapping if one already exists. The Yes (and replace existing) option works the same as Yes, but if a reverse record for the IP address already exists it will be updated with the new hostname. This can be useful if you know there is an existing record that you want to replace. If No is selected, no reverse address will be created even if it is possible.
8. When you are done filling in the form, click the Create button at the bottom. As long as it is filled in correctly, the record will be added to the list below the form. When writing to the zone’s records file, Webmin will use the full canonical format for the record name, such as www.example.com., even if you just enter www.
9. To activate the new record so that it can be looked up by DNS clients and other servers, you will need to click the Apply Changes button on the module’s main page. If you are planning to add or edit several records, it is usually better to wait until all the changes are complete before hitting the apply button. If it is available, you can instead use the Apply Changes button at the bottom of the master zone page shown below. This uses the ndc command to tell BIND to re-read only the file for this zone, which can be much faster on a system that hosts are large number of domains.

The master zone editing page

Although the instructions above are focused on adding an Address record, the process of adding other record types to a forward zone is almost identical. The Update reverse? field does not exist, and the Address field is replaced with one or more different fields. The Record types section below explains in detail what fields are available for each type of record known to Webmin.

When adding a Reverse Address record to a reverse zone, the form is quite different. The Address field appears before the Hostname, and the hostname must always be entered in canonical form with a dot at the end, like www.example.com.. The Update reverse? field is replaced with Update forward?, which controls the automatic creation of a record in the corresponding forward zone. However, there is no option to overwrite an existing forward record – if one with the same name already exists, it will not be touched even if Yes is selected.

Every time a record is added to or updated in a zone using Webmin, its serial number will be automatically incremented. This also applies to reverse zones that are automatically updated when adding an Address record, and vice-versa. This means that when you apply the changes, other DNS servers will be able to detect that the zone has changed by comparing the new serial number with the old one that they have cached.

To edit an existing record in a zone, the steps to follow are :

1. On the module’s main page, click on the icon for the zone that you want to edit, which will bring you to the page show above.
2. Click on the icon for the type of record that you want to change, which will display a page listing all records of that type in the zone. Alternately, you can click on the All Record Types icon which will bring up a list of every single record in the zone regardless of type.
3. Click on the name of the record that you want to edit. Your browser will display a form similar to the one used for adding a record, but with the fields already filled in with the details of the existing address.
4. To re-name the record, edit the contents of the Name field. It will be shown in canonical form with a dot at the end initially, but you can change it to a name relative to the domain if you wish.
5. Adjust the Time-To-Live field in you want this record to have a different TTL, or set it to Default to make it the same as the rest of the zone.
6. If this is an Address record, change the IP in the Address field. For other record types, the fields are the same as those on the record creation form, and have the same meanings.
7. For Address records, the field Update reverse? is displayed. Selecting Yes will cause the corresponding record in the reverse zone to be have its name and address changed to match this forward record. If you change the IP so that the reverse address is no longer in the same network, it will be removed from the old reverse zone and added to the new reverse zone (if it is hosted by your server).
8. For Reverse Address records, the field Update forward? is shown instead. If Yes is selected, the corresponding Address record in its forward zone will be changed to match any changes that you make on this form.
9. Click the Save button to update the record in the zone file, and return to the list of record types.
10. To activate the changes, click the Apply Changes button back on the module’s main page.

To delete a record from a zone, click on the Delete button on the editing form instead of Save. For Address records, if the Update reverse? field is set to Yes, the corresponding Reverse Address record will be deleted as well. Apart from that, the process of deleting a record is identical no matter what type it is. The same thing happens when deleting a Reverse Address record – the matching Address record is deleted as well, as long as the *Update forward?* field is set to Yes.

The list of records in a zone is initially sorted according to the module configuration, which usually means that records will be displayed in the order that they were added. To change this, you can click on a column heading like Name, Address or Real Name to sort them by that column instead. The sorting is only temporary though, and will be lost if you return to the main page and re-open the zone. To change it permanently, see the Order to display records in field in the section on *Configuring the BIND DNS Server module*.

Related posts:

1. Creating/editing a master zone using Webmin
2. Setting up DNS using Webmin (Quick Guide)
3. How to point a sub-domain to a different IP Address or Server?
4. The BIND DNS Server module
5. Adding custom directives to VirtualHosts