Services for UNIX - Interoperability

Client for NFS in Windows 8

2012-08-01T19:26:00Z

Client for NFS in Windows 8 Now that it's been RTM'ed - it's time you should know what's new with NFS components in Windows 8 and I would like to start with Client for NFS. While there are significant changes with respect to Server for NFS component in Windows 8, Client for NFS seems to have escaped unchanged UI-wise. Not entirely really - it now support krb5p flavor of Kerberos authentication in addition to krb5/krb5i support that was introduced in Windows 7. The krb5p flavor adds privacy...(read more)

SUACommunity.com Closure

2010-07-06T22:58:35Z

SUACommunity.com Closure Last week, I was equally surprised when I received the word that SUACommunity.com is not getting the funds to continue functioning. This portal and Rodney have been the greatest assets SUA have had so far. While I would have loved Rodney continue with this portal and the work he was doing on SUA, I wish he gets to work with something much better and much more satisfying than SUA. I have been swamped with emails on the support for the tools that people downloaded from...(read more)

Proof of Concept: NFS Attributes Editor

2010-06-21T18:31:00Z

Proof of Concept: NFS Attributes Editor We come across a lot of people who have IdMU tools installed even though they don't use the NIS authentication. This, primarily, happens because they have NFS in their environment and with Windows Vista and later, the only way to get identities mapped is by way of Active Directory Lookup. Since, IdMU and NFS both use RFC2307 attributes in Active Directory and only IdMU provides a graphical tool to populate the RFC2307 attributes for users and group objects...(read more)

Using Kerberos Authentication for Server for NFS

2010-05-25T20:11:00Z

Using Kerberos Authentication for Server for NFS It has always been attributed that the NFS communication is inherently insecure and that's completely true. There are certain security options but they aren't enough to protect the data from unauthorized access. Fortunately, the NFS architecture is flexible and it allows you to plug in additional authentication methods. So, we took advantage of this fact and have implemented options to use Kerberos authetication for NFS server and client in Windows...(read more)

Synchronizing SFU Attributes with RFC2307 Attributes

2010-03-31T23:02:00Z

Synchronizing SFU Attributes with RFC2307 Attributes In a very short span of time, I received multiple requests for a script that can sync the values from SFU attributes to RFC2307 attributes. This isn't a new request but it pretty much pointed out that some information is missing and people run in to this situation which should arise in the first place. The first scenario is where Server for NIS is not at all used and LDAP authentication is implemented using SFU attributes and when AD schema...(read more)

SUA SDK for Windows 7/Windows Server 2008 R2

2010-03-23T16:49:00Z

SUA SDK for Windows 7/Windows Server 2008 R2 The news is not new and you may already be aware that the SUA Utilities and SDK pacakge for Windows 7/Windows Server 2008 R2 is released after a really long time. Just for the convenience, you can download it here - http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=dc03485b-629b-49a6-b5ef-18617d1a9804 As I pointed out earlier in a related post, this release doesn't really introduce any new features and it is mostly bug fixes...(read more)

Managing Client Groups - An Easier Approach

2009-11-13T00:43:00Z

Managing Client Groups - An Easier Approach On UNIX-based NFS servers, it's much easier to control access to the NFS shares based on host names or IP addresses. You just have to put them in the export file and it's done. It's not so difficult in Windows either - you can click on the Permission buttons on the NFS Sharing tab and add/remove hosts and control the access type and root squash option graphically. While that's easy - Server for NFS supports a concept called client groups. These groups...(read more)

Using DFS for Centralized Access to Multiple NFS Servers

2009-09-11T22:28:00Z

Using DFS for Centralized Access to Multiple NFS Servers Lately, we have seen customers who are trying to utilize DFS to publish NFS shares from a single DFS server to centralize the access for the clients. This has several benefits. It removes the problem of keeping a note of what NFS server is hosting a given NFS share and also the need to mount them. While you can still map a DFS link to a drive letter, I think it would be easier to browse to the DFS server using UNC and use the shares....(read more)

Getting AD Lookup to work without UNIX Attributes tab

2009-07-16T20:03:00Z

Getting AD Lookup to work without UNIX Attributes tab The previous post talks about how to get the UNIX Attributes tab to work without installing IdMU components. In this post, I would like to talk about what attributes the NFS components expect to be populated in AD for user and group object before it can recognize them and use the information. The UNIX Attributes tab populate a lot of other attributes because it is primarily designed to assist administrators to populate the attributes that...(read more)

Using UNIX Attributes tab without installing IdMU

2009-07-13T22:11:00Z

Using UNIX Attributes tab without installing IdMU Starting with the Windows Server 2003 R2 release, Microsoft has made it clear that the AD Lookup feature would be the preferred direction to go for identity mapping between Windows and *nix when it comes to NFS access - both server and client. AD Lookup uses the information populated in UidNumber and GidNumber attributes with user and group objects in AD to map the identity information between these platforms. There's no tool that comes with...(read more)

AD Lookup with ADAM/ADLDS

2009-07-11T01:17:00Z

AD Lookup with ADAM/ADLDS With removal of UNM in Vista/W2K8, it became really problematic to map users in non-AD environments to use with Vista/LH NFS Servers and Clients. For client, a workaround was discovered which was essentially a registry tweak and did allow more than user to be able to access the resources. Now, a guide exists that details the steps to install and configure ADLDS (Active Directory Lightweight Directory Services) and to use it with NFS for UNIX identity information source...(read more)

Removal of technology: Services for Macintosh (SFM)

2009-06-24T22:22:00Z

Removal of technology: Services for Macintosh (SFM) This seems a little strange and SFM is being talked about on this blog. Well, SFM is one of the technologies that we support along with UNIX Interoperability components like NFS, NIS and SUA. Anyways, this is not news and people who have used SFM would have noticed by now that SFM is not part of Windows Server 2008 and later releases. This technology has been in the maintenance mode since long and didn't change much since the Windows NT 4...(read more)

Windows 7 SUA SDK

2009-06-24T21:51:00Z

Windows 7 SUA SDK A lot of people have been enquiring about the Windows 7 SUA SDK. There is a lot of anticipation since Windows 7 has already raised the bar on the other fronts and now people have high expectations for SUA SDK that would be released for Windows 7 SUA. The picture is not as good - there are no new features being added to SUA with Windows 7. You would not see any new ported utilities or libraries. It will be just the bug fixes that have been reported on previous SDK and not much...(read more)

Can I Set Up User Name Mapping in Windows Vista?

2009-03-27T23:01:00Z

Can I Set Up User Name Mapping in Windows Vista? Unfortunately, no if you don't have a SFU 3.5 or W2K3 R2 machines on the network that is running User Name Mapping service. This has been a major disappointment with NFS deployments using Windows Vista. However, there is a tiny little good news for you if you are looking for a way to enable Client for NFS in Windows Vista to be able to do something other than anonymous mounts. There is a registry tweak that you can modify to tweak Vista NFS client...(read more)

NFS and SUA in Windows 7

2009-01-23T22:48:00Z

NFS and SUA in Windows 7 Finally, the Windows 7 beta is released to the public and we can now experience it ourselves. The PSS people in Microsoft are always excited to try their hands on the latest betas and Windows 7 is not an exception. The first thing that we did, after exploring the new GUI experience, was to add Client for NFS and Subsystem for UNIX-based Applications (SUA) components. The addition is completely alike Windows Vista so no surprises here but it was much faster than Vista...(read more)

Limitation with Active Directory Lookup feature in Microsoft Services for NFS

2008-12-16T01:25:00Z

Limitation with Active Directory Lookup feature in Microsoft Services for NFS The Active Directory Lookup feature that was introduced with Windows Server 2003 R2. This feature greatly simplifies the UNIX identity information management but has its own set of limitation. I thoughy I'll document them here - 1. If you are using Client for NFS in conjunction with Active Directory lookup, the client will not send the secondary groups information of the user to the server. This is a limitation in...(read more)

Set up Services for Network File System in Windows Server 2008

2008-12-16T01:03:00Z

Set up Services for Network File System in Windows Server 2008 The Microsoft Services for NFS continues to be the part of the operating system in Windows Server 2008 and seems we will see more improvements when Windows Server 2008 R2 is released. In Windows Server 2008, a major change from the Windows Server 2003 R2 is the elimination of User Name Mapping service. Although, you can still use an existing UNM server to fetch the UNIX Identity information on a Windows Server 2008 system, it doesn...(read more)

All (well, almost) about Client for NFS - Configuration and Performance

2008-04-14T08:42:00Z

All (well, almost) about Client for NFS - Configuration and Performance

I was looking at the referrals this blog gets and I noticed that a lot of times people look for information on Client for NFS in Services for UNIX, Windows Server 2003 R2 or in Windows Vista and come to this blog, but I don't really have much useful information on installation, configuration and performance on Client for NFS. Now, that will not be the case.

I have received requests to put together something about Client for NFS since there doesn't seem to be a detailed single document which talks about it. There are KB articles which cover installation and configuration of Client for NFS. There are also some of them about issues and registry settings to help optimize the settings for CNFS.

Since it has also been a long time I have spent time on this blog, I guess it's high time I talk about Client for NFS and add some value to my blog.

Client for NFS is a very important offering from Microsoft for small and big enterprises to integrate their Windows systems with existing UNIX based environment. It now comes with RFC2307 support as well. It's one of the most simple component among Services for UNIX components. Client for NFS doesn't really ask for any configuration/restarts in most of the installations and offers true out-of-the-box NFS connectivity. You can see in the following screen shot how Client for NFS can be added/removed if Services for UNIX software is already installed -

In Windows Server 2003 R2, you can find CNFS listed in "Microsoft Services for NFS" under "Other File and Print Services" -

And, on a Windows Vista Enterprise/Ultimate systems, here's how you can add it -

Once you have installed Client for NFS, you are ready to start connecting to UNIX NFS shares where anonymous access is allowed. If your environment doesn't have any such shares to test connectivity, you now need to configure this system to fetch UNIX identity information from an existing User Name Mapping server or configure one if it is not already running.

See these posts to learn more about User Name Mapping, especially Configuring User Name Mapping, Configuring User Name Mapping - Part 1, Configuring User Name Mapping - Part 2 (Simple Mapping) and Configuring User Name Mapping - Part 3 (Advanced Mapping).

With Windows Server 2003 R2 and Windows Vista, you can configure Client for NFS to directly fetch this information from AD if it's already there since they offer RFC2307 support. In fact, you can use any RFC2307 compliant directory service.

Configuration for Client for NFS is over with this and you can start using it. To connect to NFS shares, you can use the same built-in mechanisms as you would with a normal Windows share. In fact, you also get to use the familiar mount command to use.

Run the nfsadmin client command to see what options Client for NFS is configured to use. It might show something like this and is self-explanatory -

The File Setting in the above screen shot is the UMASK value Client for NFS will use when you create a new file or a folder on an NFS mount.

You can use NET command, the mount command which comes with it or the "Map Network Drive..." to map a drive to remote NFS shares. You can also browse the network and look for system which export NFS shares using "Network Neighborhood" or "My Network Places" since Client for NFS adds "NFS Network" under "Entire Network" for people who find it easier to search for machines they would like to connect to.

The mount command is useful because it lets you override the default parameter which applies to the NFS connections from this computer. The help for mount command can be displayed by running it with /? command line switch -

It uses a similar syntax like the NET USE command but it's not completely identical. For example, following is what you can use to map z: drive a remote NFS export -

mount \\servername\sharename z:

On the performance side, Client for NFS is tuned with parameters which suit most of the environments, but still there are things which can be tweaked to see if it helps you the way you want it -

Read and Write buffers - This can tuned from the MMC snap-in or per mount using the mount command. If you do it using the mount command, the syntax will look like -
mount -o rsize=16,wsize=16 \\servername\sharename drive
The default is 32 KB and works perfectly in most of the scenarios.
Case-sensitive mounts - Since Windows is not case-sensitive, enabling case-sensitive option while mounting the NFS shares can reduces the time taken to look up a file on the server. When this is option is not turned on (which is the default behavior), Client for NFS can perform multiple lookups to locate a single file and that will show up as a performance problem
This can only be done using the mount command and the syntax to do this is -
mount -o casesensitive \\servername\sharename drive:
8.3 name cache - As with Windows, Client for NFS also generates a 8.3 format name for the files on the NFS shares being accessed using Client for NFS. This adds up to the processing overhead. Turning off this option is recommended for performance gain. This is done with a registry change and this KB article explains the steps.
8.3 name generation in Windows Server 2003 R2 and later releases are permanently turned off for the same reason.
NFS Caching - NFS v3 uses caching to improve performance but this can be problematic in certain scenarios. Create "RemoteWriteCache" and "FileAttributeCache" DWORD values under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Client for NFS\CurrentVersion\Users\Default\Cache and set these to 0 to disable caching.
Folder Content Caching - Client for NFS also caches the folder contents for 30 seconds to avoid performing lookups to the NFS servers. This can sometimes result in delayed folder content refresh. Follow the steps in this knowledgebase article to disable it.
Set this registry setting to a value between 5-25.

Something worth taking a note - although the settings related to different aspects of caching may improves things on the client side, they can have performance percussions on the server side because when caching is not at work, the client may place more calls to the server and depending on the server and network conditions, it may cause the server to sweat more than it would normally. It's completely up to you to decide who would you like to work more for you - NFS client or the server.

Configuring User Name Mapping - Part 3 (Advanced Mapping)

2008-01-25T02:20:00Z

Configuring User Name Mapping - Part 3 (Advanced Mapping)

Simply said - when you map users and groups manually with their UNIX counterparts, it's called Advanced Mapping.

From the last post on User Name Mapping, you may be aware that Simple Mapping automatically creates maps for all users and group who have the same names in your Windows and UNIX environment. It is possible that you aren't lucky enough to have the same names for users and groups in both the environments. Sometimes, you would want better control on this aspect and may not want to map all the users and groups automatically.

Advanced mappings can be used in such cases. Easy to configure - turn off Simple Maps in User Name Mapping Configuration and map them manually. You can read this page to see how it can be done in a Windows Server 2003 R2 environment.

In Services for UNIX 3.x environments, you can do by using the Services for UNIX Administration console. Select User Name Mapping in the left pane, define the UNIX data source and click on Apply -

To proceed further, click on Mappings in the right pane. You can now click on Show User Mappings or Show Group Mappings depending on what you want to do -

Now, you can display the users/groups in both Windows and UNIX side. Select the objects in both lists and click on Add. You're done.

Configuring User Name Mapping - Part 2 (Simple Mapping)

2007-10-02T17:45:00Z

Configuring User Name Mapping - Part 2 (Simple Mapping)

Continuing the discussion from Configuring User Name Mapping - Part 1 - I will explain how to get Simple Mappings done in this post.

To rephrase, User Name Mapping (UNM) bridges the gap between the different user identification used in Windows and UNIX worlds. It's SID which identifies an object in Windows and Active Directory environment but it's UID and GID when it's a UNIX system in question. UNM is also a core authentication component in SFU World. When we are using it in conjunction with Server for NFS, UNM authenticates the incoming NFS access requests. With Client for NFS, it determines the effective UID and GID to be sent with the NFS requests to UNIX NFS servers.

UNM also provides a single point identity mapping database for all the machines running Server for NFS, Client for NFS and Interix/SUA components. For people looking for availability and clustering capabilities - you can configure UNM Server Pools and you can also run UNM on cluster nodes to achieve load balancing.

More on it later, back to Simple Mapping...

To match the Windows and UNIX identities, UNM uses Windows SAM or Active Directory to identify Windows users and UNIX files (/etc/passwd and /etc/group) or NIS domains as sources for identifying user and group information from UNIX perspective. This information is then mapped using Advanced and Simple Maps. Advanced maps are the ones that you create manually using the Administration Console while the Simple Maps are created automatically between the users and groups which have same names in Windows and UNIX databases.

It doesn't take much when creating Simple Maps apart from configuring basic things (I am assuming that you have installed the User Name Mapping service already and it's started).

First, you need to copy over the /etc/passwd and /etc/group files from your UNIX systems. Filter/Merge them so that they don't have any system account and duplicate UID/GID allocations. Now you can run this command -

mapadmin adddomainmap -d NTDomain -f Passwd/GroupDirectory

This command enables the Simple Mapping between the users and groups in Windows domain which is specified in place of NTDomain and the UNIX passwd/group files which have been stored under the directory specified in place of Passwd/GroupDirectory.

Now, you can run the following command to list all the maps -

mapadmin list -all

This lists all the maps which have been created. From my lab system -

The first command we ran is equivalent of making the following changes using the GUI -

Defining the UNIX files as the data source -
Enabling Simple Maps -
Displaying the Simple Maps -

It also takes care of enabling and creating Simple Maps for groups.

This KB article talks about installation and more command line options. I will soon post information in the form of Part 3 on UNM and talk about Advanced Mappings.

SFU hot fixes in email

2007-09-07T02:05:00Z

SFU hot fixes in email

Like any other Microsoft hot fix, you can also receive SFU hot fixes in your inbox - http://go.microsoft.com/?linkid=6294451

All you need is the KB article number which describes the fix you need. While we are talking about it, the following is also important to note -

"Hotfix Information

A Hotfix is a single package that includes one or more files that is used to address a very specific customer problem with a product. A supported Hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in the previous mentioned article. Only apply it to systems that are experiencing this specific problem. This Hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next service pack that contains this Hotfix."

Why am I talking about it here?
At first, it doesn't sound like has anything to do with SFU or UNIX Interoperability components shipped with Windows. But, then users who use these components know that hot fixes get them out of many problems. I am sure a lot of them would prefer getting the hot fix using this form instead opening a case.

Before you rush to request the latest and greatest fixes for SFU or R2 components - be informed that there are a few of them which have very specific prerequisites and if they are not fulfilled, you may run in to other issues. Read below to know about them -

KB913030 - Applies only to Services for UNIX 3.5
You can install this hot fix on any system that's running Interix Subsystem, Server for NIS or Password Synchronization. It doesn't create any problems but is mentioned here since it contains some stability and reliability update for Interix subsystem and some utilities. You should install this fix before you install any other Interix subsystem hot fix which is newer than this one.

KB921599 - Applies only to Services for UNIX 3.5
Many people get confused with the information in the Kb article. This hot fix again applies only to Services for UNIX 3.5 Server for NIS and Password Synchronization components. You need this hot fix only if you have added a Windows Server 2003 R2 DC (or upgraded one of the DCs to R2) AND have also installed Server for NIS Identity Management for UNIX (IdMU) component which comes with Windows Server 2003 R2.

Since IdMU components in R2 use RFC2307 schema classes and attributes, when you install these components in SFU 3.5 environment, the installation process upgrades all of the NIS objects (NIS Domains, maps, users, groups etc.) to use R2 schema enhancements. This breaks Services for UNIX 3.5 Server for NIS and Password Synchronization components since they use a different schema. Installing this hot fix updates the SFU 3.5 Server for NIS and Password Synchronizarion binaries to use RFC2307 classes and attributes and helps SFU 3.5 and R2 IdMU components to co-exist.

KB936529 - Applicable to Services for UNIX 3.5
The previous post talks about it. Windows Server 2003 Service Pack 2 installation breaks SFU 3.5 Interix Subsystem and Password Synchronization components and this hot fix helps you to undo that. This hot fix should not be installed on Windows Server 2003 R2 SP2 systems because if you are using Password Synchronization IdMU component, this hot fix replaces the pswdsync.dll file with the one meant for SFU 3.5. As a result, Password Synchronization stop working.

If you have any questions about any SFU hot fixes, please use the Email button on the blog side bar and shoot me a mail.

Update: Windows Server 2003 SP2 breaks SFU

2007-07-11T17:05:00Z

This post discussed about a problem with SFU 3.5 Interix and Password Synchronization components which break when you install Windows Server 2003 Service Pack 2. It also lists steps to fix it manually using files from another hot fix.

Microsoft has released a new hot fix - KB936529 - which fixes this issue and removes the burden of replacing the correct files manually.

If you've installed Windows Server 2003 Service Pack 2 and running in to this problem, please get this hot fix from PSS and install it. Make sure you don't install this hot fix on an R2 system because that may break correponding R2 components.

Configuring User Name Mapping - Part 1

2007-06-06T02:02:00Z

Configuring User Name Mapping - Part 1

On this page, I have put some information about how you can configure User Name Mapping. It doesn't have the complete step-by-step kind of touch to it since that article was all about getting Server for NFS to work.

To do justice to User Name Mapping, I am beginning a series of posts which discusses different UNIX environments and how they can be used with User Name Mapping to allow Windows systems to interoperate with UNIX environment and help migrating data from UNIX systems to Windows. This post, again, will not have step-by-step guide to configure User Name Mapping. That's something to follow in the next posts.

A typical UNIX environment may use local files (/etc/passwd and /etc/group) to manage authentication and manage access. In addition to local files, a UNIX system can also make use of NIS and LDAP to authenticate users centrally. Having centralized authentication make more sense if people need to access data on NFS servers – more so because all NFS cares about is UIDs and GIDs to allow access to data.

If an environment doesn't have centralized control on user and group accounts, it presents many challenges when it comes to security and managing unique UIDs and GIDs across all UNIX systems. NIS and LDAP reduce this overhead and provide easy to manage repository of user and group accounts. They also provide mechanisms such as netgroups to further strengthen security on NFS shares.

If your environment doesn't use NIS or LDAP for authentication and if your users and groups are scattered on different UNIX systems having their own user and group naming conventions and the UIDs and GIDs are duplicated between them – you really need to make a lot of changes before you can reap the benefits of UNIX interoperability components shipped with Windows and Services for UNIX 3.5 product.

To start with – you would need to ensure that your users and group have unique UIDs and GIDs and there are no conflicts across all systems.
You, of course, need to ensure that the user and group names are unique too.

Most difficult part is to plan and change UIDs and GIDs on UNIX systems. It’s not easy but you follow some simple steps to get it done sooner than later -

Allocate a range of UIDs and GIDs for each of your UNIX system. This range needs to be calculated based on the number of users and groups created on them.
Changing the UIDs and GIDs can be done quickly using the awk command. A simple awk script can scan the /etc/passwd and /etc/group files and change the UIDs and GIDs based on the range you allocated in first step.
Changing UIDs and GIDs will immediately result in access being revoked on the local and remote file system resources since it’s based on UIDs and GIDs and not names of the users and groups. However, you can run a find command with the right syntax to search for the files and directories owned by a user’s old UID and change it to the new UID. Same applies for groups.
It becomes really easy if you can put together a script which searches and changes UIDs and GIDs on files and folders simultaneously when changing the UIDs and GIDs in /etc/passwd and /etc/group files.
Depending upon how it worked earlier, you might also have to look for accounts which belong to same users and groups on different UNIX systems and match their UIDs and GIDs so that they have same values on all of those systems.
Last and most important part is to now combine /etc/passwd and /etc/group files from all of the systems and form a single master database.
You can very well use this database to implement a centralized authentication using NIS. Check back later on this blog to look for the steps to do that.

For now, you need to move this master database to the server running the User Name Mapping service and use it configure appropriate user and group mappings.

On the other hand, things become really easy if you have NIS or LDAP already running in your environment – User Name Mapping can directly connect to your NIS servers and fetch the details to create mappings for user and group accounts.

Server for NFS and Client for NFS which ship with Windows Server 2003 R2 and Windows Vista can also talk to your RFC2307-compliant LDAP store to fetch the UID and GID information directly. This will also be featured in Windows Server 2008. It also helps you eliminate User Name Mapping service from your setup and stop worrying about mapping users and groups manually when adding new accounts (if you are not making good use of Simple Mappings).

"Network Error 53", "The data area passed to a system call is too small" or "Unknown Error"

2007-06-05T02:51:00Z

"Network Error 53", "The data area passed to a system call is too small" or "Unknown Error"

Client for NFS included with Windows Server 2003 R2 returns different errors when trying to access NFS shares on UNIX-based NFS servers. The exact error message may depend on your environment - you might get one or more from the ones mentioned above. And, at the same time, SFU 3.5 Client for NFS may work just fine.

Analyzing the network traffic may show MOUNT or NFS calls being "rejected for security reasons (5)".

The R2 Client for NFS uses high ports (>1024) to connect to NFS servers and that's known to cause the above errors. There are two ways to fix this -

Change how your NFS servers export the NFS shares and make them allow connections from high ports, or,
Add UseReservedPorts DWORD value under HKLM\Software\Microsoft\Client for NFS\CurrentVersion\Default and set it to 1. Restart the Client for NFS service to allow the change to take effect.

Should you worry about security when you change your NFS server to allow connection from high ports? The answer is NO. An excerpt from RFC2623 says so -

Many NFS servers will require that the client send its NFS requests
from UDP or TCP source ports with values < 1024. The theory is that
binding to ports < 1024 is a privileged operation on the client, and
so the client is enforcing file access permissions on its end. The
theory breaks down because:

*    On many operating systems, there are no constraints on what port
     what user can bind to.
*    Just because the client host enforces the privilege on binding
     to ports < 1024 does not necessarily mean that a non-privileged
     user cannot gain access to the port binding privilege. For
     example with a single-user desk-top host running a UNIX
     operating system, the user may have knowledge of the root user
     password. And even if he does not have that knowledge, with
     physical access to the desk-top machine, root privileges are
     trivially acquired.

On the other hand, turning off low ports check on the NFS servers ensures compatibility with NFS clients irrespective of clients using high or low ports to access the NFS servers.

Note that above mentioned errors can be caused by number of other factors as well so if the solutions mentioned above don't work for you - focus your troubleshooting on other aspects.

How User Name Mapping works?

2007-05-11T23:28:00Z

How User Name Mapping works?

User Name Mapping is the core NFS authentication component in Services for UNIX, Windows Server 2003 R2 and Windows Vista. It bridges the gap presented by difference in user identification methods used by Windows and UNIX systems. It plays equally important role for Server for NFS and Client for NFS both.

When Server for NFS receives NFS access request from a UNIX client, all it gets is UID, GID and a set of auxiliary GIDs (which represents the secondary group memberships of that user in the UNIX world). Server for NFS then typically performs the following actions to authenticate the UNIX user who’s trying to access Windows NFS share –

Server for NFS uses User Name Mapping to obtain the corresponding Windows user name or group name.
After the user name is obtained, Server for NFS connects to a domain controller (for a domain account), or to local security authority for a local user –

The domain controller authenticates the domain account using Kerberos extension called Service-For-User (S4U).
Server for NFS Authentication is needed if the user account in question is a local account. Without Server for NFS authentication, the local security authority cannot authenticate the user and access to the UNIX client will be denied.

NFS authentication may not work for domain accounts if you have domain controllers running Window 2000 operating system. S4U extensions is not supported in Windows 2000 and earlier. In such cases, you need to install Server for NFS Authentication on all of your domain controllers to get the NFS authentication to work.

When you use Client for NFS to access a UNIX NFS share, it’s the UNIX NFS Server which authenticates the Windows user at the end. Since Windows users do not have UNIX-style UIDs and GIDs, the Client for NFS gets this information from the User Name Mapping service and uses them to connect to the UNIX NFS Server.

The NFS components included with Windows Server 2003 R2 and Windows Vista have RFC2307 support and can directly fetch the UIDs and GIDs from Active Directory. This post on this same blog talks more about this feature and User Name Mapping. The Active Directory domain, however, needs to be on the R2 schema level for that to work.