DNS

NSD 4 migration and features

Team NLnet Labs

Dec 18, 2012 • 4 min read

By Wouter Wijngaards

This post describes migration to NSD4 and the new features of NSD4. An overview of the NSD 4 project is here.

Migration

The old NSD3 config file can be used without changes for NSD4. There are new config statements and some old statements are gone (and ignored by NSD4).

The nsd.db file has a new format that allows read and write. Thus the nsd.db file needs to be re-created in NSD4 format. This takes place when you start NSD4 the first time; it creates the nsd.db file. NSD4 needs write permission on the nsd.db directory for that. If you need to rollback to NSD3, run the old zonec to recreate the NSD3 nsd.db file (use nsdc rebuild).

The cron job for nsdc patch is no longer needed, because nsd.db is updated on-the-fly. It can be removed.

If you favor cron jobs, you can have a cron job that does “nsd-control write”. This would periodically write the contents of changed zones to their zonefile.

nsdc is removed, reload with kill -HUP $pid or use nsd-control reload. The SIGHUP makes NSD4 check zone file timestamps and reload changed zones. nsd-control reload is the same. SIGTERM stops NSD.

You probably want to install and enable some of the new NSD 4 features, such as set-up nsd-control and statistics. And you may want to use the new pattern config options.

Removed config options

difffile: ixfr.db is gone. This setting is no longer applicable, because the ixfr.db file is no longer used. Files are created in /tmp (configurable) now. The value is ignored by NSD4 if given in nsd.conf.

New config options

zonelistfile: zone.list. This file contains a plain text listing of the dynamically added zones and their pattern. It is read and written by NSD while it is running.

xfrdir: /tmp. This directory is used to store temporary zone transfer files. They are stored in a unique subdirectory that has few access permissions.

tcp-count: 100. This option already exists in NSD3, but in NSD4 you can increase it above 1024, like 2048, to have higher TCP capacity.

remote-control: this is a new section in the config file that configures the nsd-control remote control utility. It is very similar to unbound’s remote control configuration. With control-enable: yes you can enable it, it is disabled by default. It is bound to the loopback interface by default. See the manpage or sample config for the list of options, it is possible to set the port number and keyfile paths, and configure it to be accessible from the outside.

pattern: these allow you to bundle a set of zone config statements. Then for a zone you can include-pattern: “nameofpattern” to apply those config statements. patterns can also include other patterns. This is needed to allow the user to specify the config statement pattern for a newly added zone. But you can also use it to organise the configuration.

zone: These already exist in NSD3 and work similarly. For NSD4, they create a zone that cannot be dynamically removed because it is hardcoded in the nsd.conf file. Zones that are dynamically added can also be dynamically removed, but those zones are in the zones.list file. The zone can have the normal zone config statements, and it can also use include-pattern to apply config statements from a pattern to it.

The nsd-control Utility

You can control the NSD4 daemon with signals, SIGHUP, SIGUSR1 and SIGTERM, if you want. It reloads on SIGHUP and this includes parsing and loading changed zone files. More commands are available via the nsd-control utility. It connects over SSL with the daemon and sends the command to it, and prints the result.

To enable nsd-control you have to create the private and public keys with nsd-control-setup, run this setup script as root. Then edit nsd.conf and set remote-control: control-enable: yes in the config file. Then you should be able to use nsd-control; the nsd-control status command is a simple check if everything works.

reload [zone] : without a zone name it checks if zone files have changed, if so, loads them. If you specify the zone name (nsd-control reload example.com) it will load that zone.

repattern : this rereads the nsd.conf file without a restart. Only the zone configuration and ratelimits are updated from it. Other settings, file paths, chroot location, interfaces, and port numbers, cannot be applied and need a restart. During the restart NSD will have the permissions to bind port 53 and chroot again.

log_reopen : also done on SIGHUP, but this controls more exactly that only the logfile is reopened.

stats and stats_noreset : print statistics.

addzone name pattern : adds a new zone to the running server. If it has a zonefile this file is read in and served. If it is a slave zone, a zone transfer is attempted.

delzone name : removes zone.

write [zone] : write a zone contents from nsd.db to its zonefile in text format. writes all changed zones, but if you specify a particular zone, it writes that zone only.

notify [zone] : for master zones, send notifies to its slaves. If you specify a name, only that zone, otherwise all master zones.

transfer [zone] : for slave zones, attempt a zone transfer from the masters. If you specify a name, only that zone, otherwise all slave zones.

force_transfer [zone] : same as transfer but uses full zone transfer with AXFR and does not perform a serial number check.

Statistics

With nsd-control you can get a list of statistics from NSD on demand. This makes it easier to integrate NSD into a statistics collection system. You have to compile with — enable-bind8-stats for this. In source/contrib/nsd_munin_ is an example munin plugin.

Other features

Performance increase.
Support a high zone count.
Faster zone transfers.
Add and remove zones without a restart.
Can reread zone configuration from config file without a restart.
Higher TCP service levels, more sockets.
Detect which zone files have changed.
Stores nsec3prehash on disk, and calculates incrementally after IXFR.
Domain tree does not have the small leak of domain nodes.