Difference between revisions of "BIND"

Revision as of 21:56, 31 July 2010

Bind as caching only server

These few steps show you how to install bind as a caching only server.

Install bind

# pacman -S bind

Edit /etc/named.conf and add this under the options section

listen-on { 127.0.0.1; };

Adding named to boot process

Edit /etc/rc.conf:

DAEMONS=(.. named ..)

Set resolv.conf for using the local dns

Edit /etc/resolv.conf:

nameserver 127.0.0.1

Running Bind in a chrooted environment

This is not required but improves security. If you want you may implement this feature later and skip directly to configuration section.

Preparing the chroot

Define the chroot directory, for example:

CHROOT="/chroot/named"

Create chroot directories

mkdir -m 700 -p ${CHROOT}
mkdir -p ${CHROOT}/{dev,etc,var/run/named}

To enable logging inside chroot you also need to create a log directory:

mkdir ${CHROOT}/var/log

and inside this a file named.log as per logging statement in named.conf:

touch ${CHROOT}/var/log/named.log

You may also want to access this file from /var/log:

ln -sf ${CHROOT}/var/log/named.log /var/log

Copy necessary files

cp -v /etc/named.conf ${CHROOT}/etc/
cp -v /etc/localtime ${CHROOT}/etc/
cp -Rv /var/named ${CHROOT}/var/

Create block devices

mknod ${CHROOT}/dev/zero c 1 5
mknod ${CHROOT}/dev/random c 1 8

Set permissions

chown -R named:named ${CHROOT}/var/{,run/}/named
chmod 666 ${CHROOT}/dev/{random,zero}
chown root:named ${CHROOT}
chmod 0750 ${CHROOT}

If you enabled logging (see above):

chown named:named ${CHROOT}/var/log/named.log

Prepare the rc script

cp /etc/rc.d/named /etc/rc.d/named-chroot

Edit /etc/rc.d/named-chroot and simply add "-t ${CHROOT}" to

[ -z "$PID" ] && /usr/sbin/named ${NAMED_ARGS}

so that it looks like

[ -z "$PID" ] && /usr/sbin/named ${NAMED_ARGS} -t ${CHROOT}

Prepare variables

# vim /etc/conf.d/named

CHROOT="/chroot/named"

Starting named-chroot on bootup

you probably followed the first section before, so you have to add '-chroot' to the existing named, so that it looks like this

Edit /etc/rc.conf:

DAEMONS=(.. named-chroot ..)

Start the service

/etc/rc.d/named-chroot start

Test the service

# host wiki.archlinux.org 127.0.0.1

Output should be something like this

Using domain server:
Name: 127.0.0.1
Address: 127.0.0.1#53
Aliases:

wiki.archlinux.org is an alias for archlinux.org.
archlinux.org has address 66.211.213.17
archlinux.org mail is handled by 10 mail.archlinux.org.

Script to regenerate the chroot environment

I use this script to (re)generate Bind chroot environment. A suitable location is /usr/local/sbin/updatebindchroot:

#!/bin/sh
# Prepare or update a chroot environment for running Bind
# see http://wiki.archlinux.org/index.php/Bind

. /etc/conf.d/named

# create chroot directories
mkdir -m 700 -p ${CHROOT}
mkdir -p ${CHROOT}/{dev,etc,var/{log,run/named}}

# copy necessary files
cp /etc/named.conf ${CHROOT}/etc/
cp /etc/localtime ${CHROOT}/etc/
cp -R /var/named ${CHROOT}/var/
touch ${CHROOT}/var/log/named.log

# create block devices
mknod ${CHROOT}/dev/zero c 1 5 2>/dev/null
mknod ${CHROOT}/dev/random c 1 8 2>/dev/null

# set permissions
chown -R named:named ${CHROOT}/var/{log/named.log,{,run/}named}
chmod 666 ${CHROOT}/dev/{random,zero}
chown root:named ${CHROOT}
chmod 0750 ${CHROOT}

I call this in /etc/rc.d/named-chroot just before running named:

/usr/local/sbin/updatebindchroot

Now you can edit configuration in /etc/named.conf and mappings in /var/named. Then both named and named-chroot can be used (one at a time of course). Restarting named-chroot recreates the chroot applying configuration changes. You should never edit config files residing in the chroot. This should be considered essentially as read-only.

Configuring BIND to serve DNSSEC signed zones

See DNSSEC#Bind (serving_signed_DNS_zones)

A configuration template for running a domain

In our example we use "domain.tld" as our domain.

1. Preparing some folder structure

mkdir /var/named/{pri,sec}

If using chroot:

mkdir /chroot/named/var/named/{pri,sec}

2. Creating a zonefile

# vim /var/named/pri/domain.tld.zone

$TTL 7200
; domain.tld
@       IN      SOA     ns01.domain.tld. postmaster.domain.tld. (
                                        2007011601 ; Serial
                                        28800      ; Refresh
                                        1800       ; Retry
                                        604800     ; Expire - 1 week
                                        86400 )    ; Minimum
                IN      NS      ns01
                IN      NS      ns02
ns01            IN      A       0.0.0.0
ns02            IN      A       0.0.0.0
localhost       IN      A       127.0.0.1
@               IN      MX 10   mail
imap            IN      CNAME   mail
smtp            IN      CNAME   mail
@               IN      A       0.0.0.0
www             IN      A       0.0.0.0
mail            IN      A       0.0.0.0
@               IN      TXT     "v=spf1 mx"

$TTL defines the default time-to-live for all record types. 7200 are seconds so its 2 hours.

Serial must be incremented manually before restarting named every time you change a resource record for the zone. If you forget to do it slaves won't retransfer the zone: they only do it if the serial is greater than that of the last time they transferred the zone.

3. Configuring master server

Copy the zonefile if using a chroot:

cp domain.tld.zone /chroot/named/var/named/pri/

Edit /etc/named.conf:

zone "domain.tld" IN {
        type master;
        file "pri/domain.tld.zone";
        allow-update { none; };
        notify no;
};

Copy to chroot:

cp named.conf /chroot/named/etc/

4. Configuring slave server

If using chroot:

cp domain.tld.zone /chroot/named/var/named/sec/

Edit /etc/named.conf:

zone "domain.tld" IN {
        type slave;
        file "sec/domain.tld.zone";
        masters { 0.0.0.0; };   # ip address of the master server
};

If using chroot:

cp named.conf /chroot/named/etc/

Restart the services and you're done.

BIND Resources

• BIND 9 DNS Administration Reference Book
• Pro DNS and BIND
• Internet Systems Consortium, Inc. (ISC)
• DNS Glossary