Naming Services with ClearOS
This guide will cover name-to-IP facilities and services available through ClearOS. It will also discuss interaction with other popular name server systems.
DNS vs. WINS
Back in the early days of the internet lists of IP addresses were maintained at disparate locations in order to properly communicate between servers at various campuses. Because these lists were changing and were difficult to maintain as authoritative, the DNS (Domain Name Service) system was born. This solved the problem over how to communicate effectively when the scope of the system was unknowns. This worked from the premise that you knew the name of the resource you wanted, but not the location.
WINS was created to solve an altogether different problem. On small localized networks the need to see resources that are currently available was the key factor. In this situation, knowing where the resource is was less important that knowing that it was available. Also, a requirement to see resources when the resource name was unknown was also a requirement. For this purpose, a method of discovery was key. This discovery method, however, made this system unscalable and it is the primary reason why it is less used today. But some throw-backs exist from this bygone era that can create confusion and frustration for network users and admins alike.
| || DNS || WINS
|Resolves IP to names|| X || X
|Resolves IP to FQDN names|| X ||
|Resolves IP to short names|| X || X
|Can enumerate workgroups|| * || X
|Discoverable|| * || X
|Scalable|| X ||
|Works with network neighborhood|| * || X
Key: X=Can do it. *=Method available under certain circumstances.
While DNS and WINS overlap in many respects, they are not mutually exclusive. In fact, most older machines will try both. Newer Windows Workstations may or may not perform WINS lookups if the setting has been disabled. Additionally, if WINS is not working from the server infrastructure side, it is more difficult to tell. For DNS, the obvious clue is that it isn't working is that the Internet will also NOT function.
DNS on ClearOS
There are several strategies for the deployment of DNS on ClearOS. ClearOS comes standard with a DNS caching engine called DNSMASQ.
WINS on ClearOS
WINS is available on ClearOS through the Samba daemon called 'nmb'. The default settings listed below indicate how the Samba service will behave on the network.
|announce as||string||Operating system that Samba will announce itself as.||N T Server||Global
|announce version||numeric||Version of the operating system that Samba will announce itself as.||4.5||Global
|browsable (browseable)||Boolean||Allows share to be displayed in list of machine resources.||yes||Share
|browse list||Boolean||If yes, allows Samba to provide a browse list on this server.||yes||Global
|auto services (preload)||string (share list)||List of shares that will always appear in the browse list.||None||Global
|default service (default)||string (share name)||Name of a share (service) that will be provided if the client requests a share not listed in smb.conf.||None||Global
|local master||Boolean||If yes, allows Samba to participate in browsing elections.||yes||Global
|lm announce||yes, no or auto||Enables or disables LAN Manager-style host announcements.||auto||Global
|lm interval||numeric||Frequency in seconds that LAN Manager announcements will be made if activated.||60||Global
|preferred master (prefered master)||Boolean||If yes, allows Samba to use the preferred master browser bit to attempt to become the local master browser.||no||Global
|domain master||Boolean||If yes, allows Samba to become the domain browser master for the workgroup or domain.||no||Global
|os level||numeric||Operating system level of Samba in an election for local master browser.||0||Global
|remote browse sync||string (list of IP addresses||Samba servers to synchronize browse lists with.||None||Global
|remote announce||string (IP address/workgroup pairs)||Subnets and workgroups to send directed broadcast packets to, allowing Samba to appear in their browse lists.||None||Global
Common problems to operating a Samba 3 domain may come in the form of misconfiguration of naming services or an inability to access via NBT (which happens to be my favorite acronym of of acronyms; it stands for Network Basic Input/Output System Over Transmission Control Protocol/Internet Protocol). Two commands exist (one in Windows, and the other in POSIX/Linux/Unix) for determining if access over the network is even possible for for CIFS/SMB.
If you have trouble with either of these commands then you may have problems with your server or your network which prohibit NBT.
The nbtstat command in windows can be run at command line from your windows workstation. It can check the address of the server to see if the workgroup and servername exist and whether the appropriate NBT framework exists for communication. You will need the IP address of the server. For our example we use 192.168.1.1. It is important that you use a capital A in the command.
nbtstat -A 192.168.1.1
nmblookup is the Samba equivilent of nbtstat and has more more features. It is similar to nbtstat.
[root@system samba]# nmblookup -A 192.168.2.1
Looking up status of 192.168.2.1
SERVER <00> - H
SERVER <03> - H
SERVER <20> - H
..__MSBROWSE__. <01> - H
DOMAIN <1d> - H
DOMAIN <1b> - H
DOMAIN <1c> - H
DOMAIN <1e> - H
DOMAIN <00> - H
MAC Address = 00-00-00-00-00-00
Another area to check is to make sure that WINS is actually happening on your workstation. You can validate that your workstation has a WINS server by running:
If your workstation does NOT have a WINS entry that is valid, you WILL have problems. It is possible to use ONLY DNS for access but it is NOT recommended. Also, if your server exists on a different subnet, you will need WINS because broadcasts for names WILL fail.