HP Rp3440-4 - 9000 - 0 MB RAM Guida rapida

Configuring and Troubleshooting MS DFS links in an HP

CIFS Server (Samba) Environment

Executive summary............................................................................................................................... 2

What IS MS DFS? ............................................................................................................................ 2

Configuring MS DFS on HP CIFS Server ................................................................................................. 2

Test environment .............................................................................................................................. 2

Configuration details ........................................................................................................................ 3

Modifying the smb.conf file: .......................................................................................................... 3

Creating the MS DFS links: ............................................................................................................ 4

New to SAMBA 3.x:..................................................................................................................... 5

Testing our MS DFS environment........................................................................................................ 6

How it works ................................................................................................................................... 9

Redundant MS DFS links ................................................................................................................. 11

Troubleshooting MS DFS on HP CIFS Server.......................................................................................... 13

Problem 1: The network path was not found...................................................................................... 13

Problem 2: Logon failure: unknown username or password. ................................................................ 18

Summary .......................................................................................................................................... 19

For more information.......................................................................................................................... 19

Executive summary

HP CIFS Server (Samba) has the ability to host Microsoft Distributed File System (MS DFS). With

careful planning, this can enable you to create a virtual smb file and directory tree spanning multiple

servers and file systems. This whitepaper presents a sample configuration of MS DFS on an HP CIFS

Server and discusses several potential pitfalls encountered in a MS DFS environment.

What IS MS DFS?

MS DFS, put simply, is an agreed upon set of protocols implemented within the CIFS (Common

Internet File System) protocol to enable links to be created within a CIFS Share that point to shares on

OTHER CIFS Servers, and for those links to be followed by a client accessing them. For the purposes

of this paper, we will configure an HP CIFS Server (version 2.2k), available from

http://software.hp.com, with a single share, with files and directories LOCAL to the server as well as

MS DFS links to shares on a WIN2k and WIN2k3 server. All of the information contained in this

paper is equally applicable to HP CIFS Server revisions based on 2.2.x OR 3.x versions of Samba

unless otherwise specified. This information should also be applicable to these versions of Samba

running on Linux. We will use a Windows/XP client for testing.

Configuring MS DFS on HP CIFS Server

Test environment

We will be using a combination of HP CIFS Server, Win2k and Win2k3 servers, and a Windows/XP

client for the examples in this paper.

Table 1: Test Environment

HP CIFS Server name rkm-nt

MS DFS enabled share name Dfsroot

MS DFS link linka -> \\ceres\shared_stuff

MS DFS link linkb -> \\mccall\shared_stuff

Win2k server name Ceres

Win2k Share name shared_stuff

Win2k3 server name Mccall

Win2k3 Share name shared_stuff

Windows Xp client name Mccallevo

Xp Username FreddieTheFish

Figure 1 gives us a picture of our test environment.

Figure 1: MS DFS Test Environment

Configuration details

There are three steps to configuring MS DFS on an HP CIFS Server. Two modifications to the

/etc/opt/samba/smb.conf file and the actual creation of the MS DFS links in the HP-UX file system

directory that is hosting the MS DFS root. Notice that ALL of the modifications are done on the HP

CIFS Server – the windows servers that contain the actual shares being linked to require no special

attention.

Modifying the smb.conf file:

[global]

workgroup = DON1

NetBIOS name = RKM-NT

server string = Samba Server

security = DOMAIN

encrypt passwords = Yes

Server:rkm-nt

Dfsroot

linkb

linka

Client:mccallevo

Server:ceres

Shared_stuff

Server:mccall

Shared_stuff

password server = ceres

log level = 10

syslog = 0

log file = /var/opt/samba/log.%m

max log size = 1000

host msdfs = Yes

read only = No

[dfsroot]

path = /dfsroot

msdfs root = Yes

Note the two red colored parameters above in [global] and [dfsroot],

respectively:

‘Host msdfs = yes’: This parameter must be set to yes to enable samba to

host MS DFS links in individual shares.

‘msdfs root = yes’: This parameter is set to yes in any share that will

contain MS DFS links to other servers. In this case, we have defined a

single share with this property, called ‘dfsroot’. It points to the HP-UX

directory ‘/dfsroot’.

Creating the MS DFS links:

# cd /dfsroot

# ln -s msdfs:ceres\\shared_stuff linka

# ln -s msdfs:mccall\\shared_stuff linkb

# ll

total 0

lrwxrwxrwx 1 root sys 23 Nov 2 12:35 linka -> msdfs:ceres\shared_stuff

lrwxrwxrwx 1 root sys 25 Nov 2 12:35 linkb -> msdfs:mccall\shared_stuff

NOTE: Compare the format of the ‘ll’ output to the ‘ln –s’ command – we

had to ‘escape’ the ‘\’ in the ‘ln’ command. One of the more commonly

made mistakes while setting up DFS links for samba is NOT having the

appropriate number of backslashes in the ‘ln –s’ command. A properly

formatted MS DFS link will take the form:

msdfs:<servername>\<sharename>

NOTE: Currently the symbolic names used in MS DFS links must be in

lowercase.

New to SAMBA 3.x:

A new version of HP CIFS Server, A.02.01.01, was released in February 2005. The information in

this paper is equally applicable to this release, which includes ADDITIONAL MS DFS functionality,

enabled by the share level option ‘msdfs proxy’. This option effectively allows an entire SHARE to be

redirected vi MS DFS referral to a share on another server. For instance, consider the following

share definition in the smb.conf file:

[dfsproxy]

msdfs root = yes

msdfs proxy = \ceres.alf.cpqcorp.net\shared_stuff

When a user connects to THIS share, he will get an MS DFS referral to the share named ‘shared_stuff’

on the server ‘ceres.alf.cpqcorp.net’. This is in contrast to having a share that points to a local

directory which has MS DFS LINKS defined IN the local directory. NOTE the use of the FQDN (fully

qualified domain name) in the server portion of the proxy definition. This allows for clients who may

not be able to find the referred server via NetBIOS to resolve the name via DNS.

Testing our MS DFS environment

Now that we have configured the HP CIFS Server to offer a couple of MS DFS links, let ’s see it in

action. For this purpose, we have created a single file on each of the linked shares:

\\ceres\shared_stuff: filename=ceres_test.txt

\\mccall\shared_stuff: filename = mccall_test.txt

Figure 2: Shares and files on CERES and MCCALL

Let’s use our Windows/XP client ‘mccallevo’ to connect to these shares THROUGH the MS DFS links

we have set up on the share \\rkm-nt\dfsroot.

Figure 3: MS DFS links 'linka' & 'linkb'

Notice from Figure 3 that these links show up as standard folders.

When we click on the ‘linkb’ folder, we get:

Figure 4: Contents of 'linkb'

And we can see in Figure 4 that, indeed, the file we put on the \\mccall\shared_stuff directory DOES

show up. So the redirection through the MS DFS link was successful. We clicked on a ‘directory’ in

our \\rkm-nt\dfsroot share, and ended up on the ‘shared_stuff’ share on the ‘ceres’ server.

If we click on the folder ‘linka’, we are also successful.

Figure 5: Contents of 'linka'

So, we have demonstrated that by connecting to a single HP CIFS Server, ‘rkm-nt’ we are able to

actually access files on completely independent servers.

How it works

The mechanism behind this is interesting. What actually happens behind the scenes is this.

Client connects to a HP CIFS Server share that is hosting MS DFS links, and attempts to access one of

these links for the first time (for instance, clicking on ‘linka’ in the Explorer window open to the

‘dfsroot’ share on rkm-nt).

HP CIFS Server recognizes that this is a MS DFS link, and returns an ERROR to the client. The error

that is returned is NT_STATUS_PATH_NOT_COVERED. An MS DFS aware client (such as

Windows/XP) recognizes this special error code as a signal that the resource is a MS DFS link. This

triggers the client to send an NT_TRANSACT2 request for a MS DFS referral.

HP CIFS Server responds to this NT_TRANSACT2 request with a MS DFS referral which contains the

server and share name the client should refer to.

The client uses this information to make a direct connection to the \\server\sharename in the referral,

and from that point on the client works directly with the referred server.

The following two screen snapshots from an Ethereal4 trace of the client ‘mccallevo’. Clicking on the

‘linkb’ directory in the ‘dfsroot’ share on the HP CIFS Server ‘rkm-nt’ illustrates the network traffic

which supports this transaction.

Figure 6: Highlighted line shows client request for info on linka, the MS DFS link. Note the response immediately after, with the

Error: STATUS_PATH_NOT_COVERED

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