$TTL 30M
@   IN  SOA     localhost. admin.sdsys.ru. (
        2018071202  ;Serial
        30M         ;Refresh master->slave
        2M          ;Retry on master not responding
        2W          ;Expire to be authoritative
        15M         ;Minimum TTL
)
; Specify our two nameservers
@		IN	NS		localhost.

; Define hostname -> IP pairs which you wish to resolve