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10. Configuring a DNS server

To configure your DNS server, you should go through several steps:

Install the DNS service onto your system

We have started supporting DNS since calculate-server 2.1.4.
We use_BIND_, a common DNS server.

Before installing, make sure that BIND has been compiled with support of sdb_ldap.

Also check what you have LDAP installed. If LDAP is not on your system, install it with:

cl-setup ldap

To install the DNS service, execute:
cl-setup dns

To install the service with trusted networks:

cl-setup -a dns

Note: The time to live (TTL) of a DNS record is 178600 seconds.

Manage the DNS service

Jargon:
  • DNS zone - a segment of the domain name space.
  • master DNS zone - the main storage area for the records.
  • slave DNS zone - a record area subordinated to the master zone.
  • forward DNS zone - an area storing the records for matching the domain name to the IP address.
  • reverse DNS zone - an area storing the records for matching the IP address to the domain name.
  • authoritative server - the server used to store a DNS zone, whose records are considered authoritative for other DNS servers.
  • SOA record - recorded zone description.
  • NS record - authoritative domain name server.
  • A record - matching the domain name to the IP address.
  • PTR record - matching the IP address to the domain name.
  • CNAME record - matching on domain name to another.
  • MX record - matching the domain name to the domain names of the mail servers.

Creating a DNS zone

To create a DNS zone, use the cl-dns-zoneadd command.

Create a master DNS zone

Create a zone with an authoritative server in your zone:

cl-dns-zoneadd -n <zone name> --server <authoritative server name> --ipserver <authoritative server ip>

Create a zone with an authoritative server in another zone:
cl-dns-zoneadd -n <zone name> --server <authoritative server name>

Examples:

cl-dns-zoneadd -n test.ru --server test.ru --ipserver 10.0.0.34

  • The forward zone "test.ru" will be created;
  • Reverse zone 0.0.10.in-addr.arpa will be created, if it does not exist yet;
  • An A record will be created in the "test.ru" zone, containing test.ru corresponding to 10.0.0.34;
  • An NS record will be created in the "test.ru" zone, containing test.ru;
  • If reverse zone 0.0.10.in-addr.arpa was created, an NS record will be created for it, containing test.ru.
cl-dns-zoneadd -n test.ru --server ns.test.ru --ipserver 10.0.0.34
  • The forward zone "test.ru" will be created;
  • Reverse zone 0.0.10.in-addr.arpa will be created, if it does not exist yet;
  • An A record will be created in the "test.ru" zone, containing test.ru corresponding to 10.0.0.34;
  • An NS record will be created in the "test.ru" zone, containing ns.test.ru;
  • If reverse zone 0.0.10.in-addr.arpa was created, an NS record will be created for it, containing test.ru;
  • A PTR record will be created in reverse zone 0.0.10.in-addr.arpa, containing 10.0.0.34 corresponding to ns.test.ru, if it does not exist.
cl-dns-zoneadd -n 10.0.10.0/24 --server test.ru
* Reverse zone 10.0.10.in-addr.arpa will be created for network 10.0.10.0/24; * An NS record, containing test.ru, will be created in zone 10.0.10.in-addr.arpa.

Creating a slave DNS zone

Create a DNS zone:

cl-dns-zoneadd -t slave -n <zone name> --servers <storage servers' ips of the master zone for this zone>

Examples:
cl-dns-zoneadd -t slave -n slave.ru --servers 10.0.0.3,10.0.10.5
  • A subordinated forward zone, slave.ru, will be created; data will be fetched for it from the main slave.ru zone located on DNS servers 10.0.0.3 and 10.0.10.5.
cl-dns-zoneadd -t slave -n 10.0.0.0/24 --servers 10.0.0.3
* A subordinated reverse zone will be created for network 10.0.0.0/24 - 0.0.10.in-addr.arpa; data will be fetched for it from the main zone, 0.0.10.in-addr.arpa, located on DNS server 10.0.0.3.

Modifying a DNS zone

To modify a DNS zone, use the cl-dns-zonemod command.

You can only modify the options for a master zone.

cl-dns-zonemod  -n <zone_name or network> <options>

where:
zone_name is used for modifying a forward zone,
network is used for modifying a reverse zone.

Zone modification options:

  • --server - changing the domain name of the main authoritative server in the zone
  • --ip - changing or adding, if absent, the IP address of the zone (the A record modified or added)
  • --mx - modifying or adding, if absent, the MX records of the zone (the domain names of the mail servers modified or added)
  • --mxmod - replacing one domain name of a mail server with another, in the MX record of the zone (a mail server domain name modified)
  • -- email - changing the email address of the zone administrator (root@zone_name by default)
  • --servers - modifying the list of all authoritative servers in the zone (zone NS record)
  • --refresh - time interval before the zone is initialized in seconds or a figure + (M stands for minutes, H stands for hours, D stands for days and W stands for weeks)
    The default value is 8H (8 hours).
  • --update - time interval after a zone initialization fail before the zone is initialized again
    The default value is 2H (2 hours).
  • --expiry - time interval before zone data is considered obsolete on secondary DNS servers when unable to connect to the main DNS server
    The default value is 2W (2 weeks).
  • --minimum - time interval of storing information on failed calls in the zone
    The default value is 2H (2 hours).

Examples:

cl-dns-zonemod -n test.ru --email admin@test.ru

Modifies the email address of the zone administrator.

cl-dns-zonemod -n test.ru --refresh 10H

Modifies the zone refresh interval (10 hours)

Deleting a DNS zone

To delete a DNS zone, use the cl-dns-zonedel command.

cl-dns-zonedel -n <zone_name or network>

where:
zone_name is used for deleting a forward zone,
network is used for deleting a reverse zone.

Examples:

cl-dns-zonedel -n test.ru

The forward zone test.ru will be deleted.

сl-dns-zonedel -n 10.0.0.0/24

Reverse zone 0.0.10.in-addr.arpa will be deleted.

Deleting MX records for a zone

Example:

cl-dns-zonedel --mx -n test.ru

The MX records for the test.ru zone (domain names of mail servers for zone) will be deleted.

Deleting an A record for a zone

Example:

cl-dns-zonedel --ip -n test.ru

The A record for the test.ru zone (zone IP) will be deleted.

Creating a DNS record

To create a DNS record, use cl-dns-recadd.

To create a record, you will have to create a master zone where this record will be put.

For an A record (host.test.ru --> 10.0.0.4 ), a forward master zone must be created (test.ru).

For a PTR record (10.0.0.4 --> host.test.ru), a reverse master zone must be created (0.0.10.in-addr.arpa)

Creating an A record

Create records: examples

Create an A record and a PTR record. You will have to create a forward zone and a reverse zone first, respectively test.ru and 0.0.10.in-addr.arpa.
cl-dns-recadd --host host.test.ru --ip 10.0.0.66
  • A record will be created in the forward zone test.ru, host.test.ru corresponding to 10.0.0.66.
  • A record will be created in reverse zone 0.0.10.in-addr.arpa, 10.0.0.66 corresponding to host.test.ru
Create an A record only. A forward zone, test.ru, must be created first.
cl-dns-recadd --autoptr off --host host.test.ru --ip 10.0.0.66
  • A record will be created in the forward zone test.ru, host.test.ru corresponding to 10.0.0.66.

Creating A, MX and PTR records

Below is an example of creating an A record, an MX record and a PTR record. Begin by creating a forward and a reverse zones, test.ru and 0.0.10.in-addr.arpa, respectively.
cl-dns-recadd --mx mail1.test.ru,mail2.test.ru --host host2.test.ru --ip 10.0.0.69
  • A record will be created in the forward zone test.ru, host2.test.ru corresponding to 10.0.0.69.
  • The MX record will be created in the forward zone test.ru, host2.test.ru corresponding to two mail servers, mail1.test.ru (priority 10) and mail2.test.ru (priority 20)
  • A record will be created in reverse zone 0.0.10.in-addr.arpa, 10.0.0.69 corresponding to host2.test.ru

Creating A and MX records

Example создания A записи и MX записи.Here is an example of creating an A record and an MX record. First of all, create the test.ru forward zone:
cl-dns-recadd --autoptr off --mx mail1.test.ru,mail2.test.ru --host host2.test.ru --ip 10.0.0.69
  • A record will be created in the forward zone test.ru, host2.test.ru corresponding to 10.0.0.69.
  • The MX record will be created in the forward zone test.ru, host2.test.ru corresponding to two mail servers, mail1.test.ru (priority 10) and mail2.test.ru (priority 20)

Creating a PTR record

Here is an example of creating a PTR record. Begin by creating a reverse zone, 0.0.10.in-addr.arpa:
cl-dns-recadd -t ptr --ip 10.0.0.67 --host host.test.ru
  • The record will be created in reverse zone 0.0.10.in-addr.arpa, 10.0.0.67 corresponding to host.test.ru

Creating a CNAME record

Here is an example of creating a CNAME record. Create a forward zone first, test.ru:
cl-dns-recadd -t cname --host host.test.ru --cname calculate.ru
  • The record will be created in the forward zone test.ru, host.test.ru corresponding to calculate.ru.

Modifying records

To modify a DNS record, use the cl-dns-recmod command.

Modifying an A record

Modifying the domain name of A and PTR records

Example:

cl-dns-recmod --host newname.test.ru oldname.test.ru

or
cl-dns-recmod --host newname.test.ru 10.0.0.5

Replaces the domain name oldname.test.ru with newname.test.ru.

Initial records:
A record oldname.test.ru corresponding to 10.0.0.5
PTR record 10.0.0.5 corresponding to oldname.test.ru

Modified records:
A record newname.test.ru corresponding to 10.0.0.5
PTR record 10.0.0.5 corresponding to newname.test.ru

Modifying the IP of A and PTR records

Example:

cl-dns-recmod --ip 10.0.0.6 10.0.0.5

or
cl-dns-recmod --ip 10.0.0.6 oldname.test.ru

Modifies the IP for the domain name oldname.test.ru

Initial records:
A record oldname.test.ru corresponding to 10.0.0.5
PTR record 10.0.0.5 corresponding to oldname.test.ru

Modified records:
A record oldname.test.ru corresponding to 10.0.0.6
PTR record 10.0.0.6 corresponding to oldname.test.ru

Modifying the domain name of an A record

Example:

cl-dns-recmod --automod off --host newname.test.ru oldname.test.ru

or
cl-dns-recmod --automod off --host newname.test.ru 10.0.0.5

Replaces the domain name oldname.test.ru with newname.test.ru.

Initial record:
A record oldname.test.ru corresponding to 10.0.0.5

Modified record:
A record newname.test.ru corresponding to 10.0.0.5

Modifying the IP of an A record
Example:
cl-dns-recmod --automod off --ip 10.0.0.6 10.0.0.5

or
cl-dns-recmod --ip 10.0.0.6 oldname.test.ru

Replaces the IP value with 10.0.0.6 for the domain name oldname.test.ru.

Initial record:
A record oldname.test.ru corresponding to 10.0.0.5

Modified record:
A record oldname.test.ru corresponding to 10.0.0.6

Modifying a PTR record

Modifying the domain name of PTR and A records

Example:

cl-dns-recmod -t ptr --host newname.test.ru oldname.test.ru

or
cl-dns-recmod -t ptr --host newname.test.ru 10.0.0.5

Replaces the domain name oldname.test.ru with newname.test.ru.

Initial records:
PTR record 10.0.0.5 corresponding to oldname.test.ru
A record oldname.test.ru corresponding to 10.0.0.5

Modified records:
PTR record 10.0.0.5 corresponding to newname.test.ru
A record newname.test.ru corresponding to 10.0.0.5

Modifying the IP for PTR and A records

Example:

cl-dns-recmod -t ptr --ip 10.0.0.6 10.0.0.5

or
cl-dns-recmod --ip 10.0.0.6 oldname.test.ru

Modifies the IP for the domain name oldname.test.ru.

Initial records:
PTR record 10.0.0.5 corresponding to oldname.test.ru
A record oldname.test.ru corresponding to 10.0.0.5

Modified records:
PTR record 10.0.0.6 corresponding to oldname.test.ru
A record oldname.test.ru corresponding to 10.0.0.6

Modifying the domain name of a PTR record

Example:

cl-dns-recmod -t ptr --automod off --host newname.test.ru oldname.test.ru

or
cl-dns-recmod -t ptr --automod off --host newname.test.ru 10.0.0.5

Replaces the oldname.test.ru domain name with newname.test.ru.

Initial record:
PTR record 10.0.0.5 corresponding to oldname.test.ru

Modified record:
PTR record 10.0.0.5 corresponding to newname.test.ru

Modifying the IP of a PTR record

Example:

cl-dns-recmod -t ptr --automod off --ip 10.0.0.6 10.0.0.5

or
cl-dns-recmod -t ptr --ip 10.0.0.6 oldname.test.ru

Replaces the IP value with 10.0.0.6 for the domain name oldname.test.ru.

Initial record:
PTR record 10.0.0.5 corresponding to oldname.test.ru

Modified record:
PTR record 10.0.0.6 corresponding to oldname.test.ru

Modifying a CNAME record

Example 1:

cl-dns-recmod --cname calculate.ru cn.test.ru

Modifies the CNAME record.

Initial record:
CNAME record cn.test.ru corresponding to acoola.ru

Modified record:
CNAME record cn.test.ru corresponding to calculate.ru

Example 2:

cl-dns-recmod -t cname --host cname.test.ru cn.test.ru

Modifies the CNAME record.

Initial record:
CNAME record cn.test.ru corresponding to calculate.ru

Modified record:
CNAME record cname.test.ru corresponding to calculate.ru

Modifying or creating an MX record

Example 1:

cl-dns-recmod --mx mail1.test.ru,mail2.test.ru test.test.ru

Replaces or, if it does not exist, creates MX records in the A record _ test.test.ru_.

Initial record:
A record test.test.ru - MX record mail.test.ru (priority 10)

Modified record:
A record test.test.ru - MX record mail1.test.ru (priority 10), MX record mail2.test.ru (priority 20)

Example 2:

cl-dns-recmod --mxmod mail2.test.ru,mailnew.test.ru test.test.ru

Modifies the MX record.

Initial record:
A record test.test.ru - MX record mail1.test.ru (priority 10), MX record mail2.test.ru (priority 20)

Modified record:
A record test.test.ru - MX record mail1.test.ru (priority 10), MX record mailnew.test.ru (priority 20)

Removing a DNS record

To remove a DNS record, use cl-dns-recdel.

Removing an A or a СNAME record

Example:

cl-dns-recdel --host test.test.ru

The A or CNAME record will be removed from test.test.ru

Removing a PTR record

Example:

cl-dns-recdel --ip 10.0.0.20

The PTR record of 20.0.0.10.in-addr.arpa will be removed (10.0.0.20 corresponding to test.test.ru)

Removing MX records from an A record

Example:

cl-dns-recdel --mx --host test.test.ru

All MX records will be removed from the A record test.test.ru

Get information on the DNS service

To get information on records and zones of the DNS service, you should use the cl-info command.

Getting information on all zones

cl-info -z dns

Getting information about a zone

cl-info -Z <zone_name or network> dns

Examples:

cl-info -Z 10.0.0.0/24 dns

Returns information on reverse zone 0.0.10.in-addr.arpa (network 10.0.0.0/24) 
cl-info -Z test.ru dns

Returns information on the forward zone test.ru

Getting information about a record

cl-info -r <record_name_or_ip> dns

Examples:

cl-info -r 10.0.0.5 dns

Returns information on the record in reverse zone 5.0.0.10.in-addr.arpa (IP 10.0.0.5)

cl-info -r test.test.ru dns

Returns information on the record in the test.test.ru forward zone.

Examples of creating a zone and adding records to it

You will have to create a zone, test.ru, as well as the following domain names:
  • test.ru - ip 10.0.0.1, a WEB server, a DNS server.
  • www.test.ru - ip 10.0.0.1, a WEB server (the CNAME record, the same server as test.ru)
  • ftp.test.ru - ip 10.0.0.5, an FTP server
  • user1.test.ru - 10.0.0.100, a user's computer

To do so, run the following commands after installing the DNS service:

  1. Creating a zone, named test.ru with an A record (test.ru --> 10.0.0.1) and a reverse zoen for network 10.0.0.0/24
    cl-dns-zoneadd -n test.ru --server test.ru --ipserver 10.0.0.1
  2. creating a CNAME record (www.test.ru --> test.ru)
    cl-dns-recadd -t cname --host www.test.ru --cname test.ru
  3. creating an A and a PTR records for the FTP server
    cl-dns-recadd --host ftp.test.ru --ip 10.0.0.5
  4. creating an A and a PTR records for the user's computer
    cl-dns-recadd --host user1.test.ru --ip 10.0.0.100

Check for the DNS server's intergrity

To check a DNS server for integrity, use the nslookup or host tools.

Once you have created a DNS zone and added records to it, you will have to display the existing records within the zone; to do this, enter:

cl-info -Z zone_name dns

Example:

The test.ru zone and records in it have been created previously.

Execute:

cl-info -Z domain.ru dns

The program returns:

Information about master DNS zone domain.ru                    
+-------------------------------------------+------------------------------+                
| Field                                        | Value                            |
+-------------------------------------------+------------------------------+
| Zone name                                | domain.ru              |
| Master autoritative server    | domain.ru                |
| NS record                                 | domain.ru               |
| A record                                    | 10.0.0.5                     |
| Email administrator               | root@domain.ru     |
| Serial number                          | 3                                 |
| Refresh                                     | 8H                              |
| Update                                       | 2H                              |
| Expiry                                         | 2W                              |
| Minimum                                   | 2H                              |
+-------------------------------------------+------------------------------+
(10 rows)

Information about A records in master DNS zone domain.ru
+-------------------------------------+-----------------+
| Domain                | ip                   |
+-------------------------------------+-----------------+
| localhost.domain.ru    | 127.0.0.       |
| calculate.domain.ru        | 10.0.0.54    |
+-------------------------------------+-----------------+
(2 rows)

Check the DNS server's intergrity based on any of the existing A records; use one of the following commands:

nslookup A_record_name DNS_server_ip

or
host A_record_name DNS_server_ip

Example:

Checking a DNS server with IP address 10.0.0.5. Zone information of domain.ru is the same as in the previous example.

Check with nslookup:

nslookup calculate.domain.ru 10.0.0.5

If the DNS service works OK, the program will return:
Server:         10.0.0.5
Address:        10.0.0.5#53

Name:   calculate.domain.ru
Address: 10.0.0.54

Check with host:

host calculate.domain.ru 10.0.0.5

If the DNS service works OK, the program will return:

Using domain server:
Name: 10.0.0.5
Address: 10.0.0.5#53
Aliases:

calculate.domain.ru has address 10.0.0.54

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