Glossary
| Important note: Some information on this page may be outdated. This note will be removed if the content has been verified to apply to the 1.0 release.
Most of the documentation on this site (and thus, this page) applies to 1.0. By far the most important change is that opencli is now called openpanel-cli. |
This page is not even close to completion.
Contents |
Objects
- Everything that has any meaning in the context of your server and can be "controlled" is represented as an object.
Domain
- dnsdomain
- DNS zone
- masterdomain
- DNS Master zone
- slavedomain
- DNS Slave zone
- alias
- A secondary aliased domain
- Email domain configuration
- ftp-user
- FTP master account
- vhost
- Virtual host configuration
Definitions
DNS
- The system that runs the name services to resolve names into ip addresses is called a Domain Name Server (DNS).
- A domain name is set up hierarchically and consist of a top level domain (like .com, .org, .net, .info, or country codes like .de, .uk, etc) followed by sub domain names. For each part of the domain name a particular DNS server is authoritative.
- A typical domain name like www.acme.de is first handled by the top level domain name registrar for the .de domain space. This DNS server points to another server for the "acme" part, which in turn can point to another server for the "www" part (e.g. the webserver).
- For every domain there is a primary or master server where its records are kept (email,subdomains,etc). A secondary or slave DNS domain acts as a backup for the master server. It is used to spread the load of DNS request, and to allow domain names to be resolved if the master DNS is temporarily down or unreachable. Records are copied from the master to slaves periodically, or when they change.
The next logical object to give special attention to is a domain. It is basicly a collection of domain-related services. It can contain domain aliases, email setup, ftp-users, vhosts, dnsdomains, etc. (for a full complement see glossary)
SOA
First Record in File (SOA) Start of Authority (SOA) is the first record in the zone file. It contains the name of the primary DNS server, which must correspond to an NS record in the file, the administrator's e-mail address and the length of time records can be cached before going back to the authoritative DNS server.
The SOA also includes data for the secondary DNS server such as the date of last update (the "Serial Number") and time intervals for checking the domain.
TTL
When changing a DNS record the changes you have made will be implemented when the Time To Live has expired AND the serial number has been changed to a higher value. Often the TTl is displayd in just a number. The number equivalents the TTL in seconds. Allthough it is possible sometimes to state it in a different like 2d for 2 days, etc...)
A high TTL will mean that it will take a long time-out to see changes you have made in your SOA Shorter TTLs can cause heavier loads on an authoritative nameserver, but can be useful when changing the address of critical services like web servers or MX records, and therefore are often lowered by the DNS administrator prior to a service being moved, in order to minimize disruptions.
DNS expiration time
Indicates when the zone data is no longer authoritative. Applies to Slaves or Secondaries DNS servers only. When the referemce values expires the slave will attempt to read the SOA record for the zone - and request a zone transfer AXFR/IXFR if the serial number has changed. If contact is made the expiry and refresh values are reset and the cycle starts again. If the slave fails to contact the master it will retry every retry period but continue to supply authoritative data for the zone until the expiry value is reached at which point it will stop answering queries for the domain. RFC 1912 recommends 1209600 to 2419200 seconds (2-4 weeks) to allow for major outages of the master. BIND Time format.
A record
The Address (A) record associates a domain name with an IP address, which is the primary purpose of the DNS system.
CNAME record
The Canonical Name (CNAME) record is used to create aliases that point to other names. It is commonly used to map WWW, FTP and MAIL subdomains to a domain name; for example, a CNAME record can associate the subdomain ftp.openpanel.com with openpanel.com.
MX record
The Mail Exchange (MX) record identifies the server to which e-mail is directed. It also contains a priority field so that mail can be directed to multiple servers in a prescribed order.
NS record
The Name Server (NS) record identifies the authoritative DNS servers for a domain. A second name server is required for redundancy, and two NS records must be in the zone file (one for the primary; one for the secondary). The secondary server queries the primary server for changes.
PTR record
The Pointer (PTR) record provides data for reverse DNS, which is used for logging the domain name and verification purposes. Also called "inverse DNS," the PTR record is an option.
TXT record
A TXT record can be used for any kind of documentation. It is also used to provide information to the SPF e-mail authentication system. See SPF.
Wildcard DNS record
A wildcard DNS record is a record in a DNS zone that will match requests for non-existent domain names. A wildcard DNS record is specified by using a "*" as the left most label (part) of a domain name, e.g. *.example.com. The exact rules about when a wild card will match is specified in RFC 1034, but the rules are neither intuitive nor clearly specified. This has resulted in incompatible implementations and unexpected results when they are used.
Vhost
Virtual hosting is a method that servers such as webservers use to host more than one domain name on the same computer, sometimes on the same IP address. There are two basic methods of accomplishing virtual hosting: name-based, and IP address or ip-based.
