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Applies to SUSE Linux Enterprise Server 11 SP4

28 Samba

Using Samba, a Unix machine can be configured as a file and print server for Mac OS X, Windows, and OS/2 machines. Samba has developed into a fully-fledged and rather complex product. Configure Samba with YaST, SWAT (a Web interface), or by editing the configuration file manually.

28.1 Terminology

The following are some terms used in Samba documentation and in the YaST module.

SMB protocol

Samba uses the SMB (server message block) protocol that is based on the NetBIOS services. Microsoft released the protocol so other software manufacturers could establish connections to a Microsoft domain network. With Samba, the SMB protocol works on top of the TCP/IP protocol, so the TCP/IP protocol must be installed on all clients.

Tip
Tip: IBM System z: NetBIOS Support

IBM System z merely supports SMB over TCP/IP. NetBIOS support is not available on these systems.

CIFS protocol

CIFS (common Internet file system) protocol is another protocol supported by Samba. CIFS defines a standard remote file system access protocol for use over the network, enabling groups of users to work together and share documents across the network.

NetBIOS

NetBIOS is a software interface (API) designed for communication between machines providing a name service. It enables machines connected to the network to reserve names for themselves. After reservation, these machines can be addressed by name. There is no central process that checks names. Any machine on the network can reserve as many names as it wants as long as the names are not already in use. The NetBIOS interface can be implemented for different network architectures. An implementation that works relatively closely with network hardware is called NetBEUI, but this is often referred to as NetBIOS. Network protocols implemented with NetBIOS are IPX from Novell (NetBIOS via TCP/IP) and TCP/IP.

The NetBIOS names sent via TCP/IP have nothing in common with the names used in /etc/hosts or those defined by DNS. NetBIOS uses its own, completely independent naming convention. However, it is recommended to use names that correspond to DNS hostnames to make administration easier or use DNS natively. This is the default used by Samba.

Samba server

Samba server provides SMB/CIFS services and NetBIOS over IP naming services to clients. For Linux, there are three daemons for Samba server: smbd for SMB/CIFS services, nmbd for naming services, and winbind for authentication.

Samba client

The Samba client is a system that uses Samba services from a Samba server over the SMB protocol. All common operating systems, such as Mac OS X, Windows, and OS/2, support the SMB protocol. The TCP/IP protocol must be installed on all computers. Samba provides a client for the different UNIX flavors. For Linux, there is a kernel module for SMB that allows the integration of SMB resources on the Linux system level. You do not need to run any daemon for the Samba client.

Shares

SMB servers provide resources to the clients by means of shares. Shares are printers and directories with their subdirectories on the server. It is exported by means of a name and can be accessed by its name. The share name can be set to any name—it does not have to be the name of the export directory. A printer is also assigned a name. Clients can access the printer by its name.

DC

A domain controller (DC) is a server that handles accounts in domain. For data replication, additional domain controllers are available in one domain.

28.2 Starting and Stopping Samba

You can start or stop the Samba server automatically (during boot) or manually. Starting and stopping policy is a part of the YaST Samba server configuration described in Section 28.3.1, “Configuring a Samba Server with YaST”.

To stop or start running Samba services with YaST, use System › System Services (Runlevel) and check winbind, smb, and nmb. From a command line, stop services required for Samba with rcsmb stop && rcnmb stop and start them with rcnmb start && rcsmb start; rcsmb cares about winbind if needed.

28.3 Configuring a Samba Server

A Samba server in SUSE® Linux Enterprise Server can be configured in two different ways: with YaST or manually. Manual configuration offers a higher level of detail, but lacks the convenience of the YaST GUI.

28.3.1 Configuring a Samba Server with YaST

To configure a Samba server, start YaST and select Network Services › Samba Server.

28.3.1.1 Initial Samba Configuration

When starting the module for the first time, the Samba Installation dialog starts, prompting you to make just a few basic decisions concerning administration of the server. At the end of the configuration it prompts for the Samba administrator password (Samba Root Password). For later starts, the Samba Configuration dialog appears.

The Samba Installation dialog consists of two steps and optional detailed settings:

Workgroup or Domain Name

Select an existing name from Workgroup or Domain Name or enter a new one and click Next.

Samba Server Type

In the next step, specify whether your server should act as a primary domain controller (PDC), backup domain controller (BDC), or not to act as a domain controller at all. By default, the server is not configured as a domain controller. Continue with Next.

If you do not want to proceed with a detailed server configuration, confirm with OK. Then in the final pop-up box, set the Samba root Password.

You can change all settings later in the Samba Configuration dialog with the Start-Up, Shares, Identity, Trusted Domains, and LDAP Settings tabs.

28.3.1.2 Advanced Samba Configuration

During the first start of the Samba server module the Samba Configuration dialog appears directly after the two initial steps described in Section 28.3.1.1, “Initial Samba Configuration”. Use it to adjust your Samba server configuration.

After editing your configuration, click OK to save your settings.

28.3.1.2.1 Starting the Server

In the Start Up tab, configure the start of the Samba server. To start the service every time your system boots, select During Boot. To activate manual start, choose Manually. More information about starting a Samba server is provided in Section 28.2, “Starting and Stopping Samba”.

In this tab, you can also open ports in your firewall. To do so, select Open Port in Firewall. If you have multiple network interfaces, select the network interface for Samba services by clicking Firewall Details, selecting the interfaces, and clicking OK.

28.3.1.2.2 Shares

In the Shares tab, determine the Samba shares to activate. There are some predefined shares, like homes and printers. Use Toggle Status to switch between Active and Inactive. Click Add to add new shares and Delete to delete the selected share.

Allow Users to Share Their Directories enables members of the group in Permitted Group to share directories they own with other users. For example, users for a local scope or DOMAIN\Users for a domain scope. The user also must make sure that the file system permissions allow access. With Maximum Number of Shares, limit the total amount of shares that may be created. To permit access to user shares without authentication, enable Allow Guest Access.

28.3.1.2.3 Identity

In the Identity tab, you can determine the domain with which the host is associated (Base Settings) and whether to use an alternative hostname in the network (NetBIOS Hostname). It is also possible to use Microsoft Windows Internet Name Service (WINS) for name resolution. In this case, activate Use WINS for Hostname Resolution and decide whether to Retrieve WINS server via DHCP. To set expert global settings or set a user authentication source, for example LDAP instead of TDB database, click Advanced Settings.

28.3.1.2.4 Trusted Domains

To enable users from other domains to access your domain, make the appropriate settings in the Trusted Domains tab. To add a new domain, click Add. To remove the selected domain, click Delete.

28.3.1.2.5 LDAP Settings

In the tab LDAP Settings, you can determine the LDAP server to use for authentication. To test the connection to your LDAP server, click Test Connection. To set expert LDAP settings or use default values, click Advanced Settings.

For more information about LDAP configuration, see Chapter 4, LDAP—A Directory Service.

28.3.2 Web Administration with SWAT

An alternative tool for Samba server administration is SWAT (Samba Web Administration Tool). It provides a simple Web interface with which to configure the Samba server. To use SWAT, open http://localhost:901 in a Web browser and log in as user root. If you do not have a special Samba root account, use the system root account.

Note
Note: Activating SWAT

After Samba server installation, SWAT is not activated. To activate it, open Network Services › Network Services (xinetd) in YaST, enable the network services configuration, select swat from the table, and click Toggle Status (On or Off).

28.3.3 Configuring the Server Manually

If you intend to use Samba as a server, install samba. The main configuration file for Samba is /etc/samba/smb.conf. This file can be divided into two logical parts. The [global] section contains the central and global settings. The [share] sections contain the individual file and printer shares. By means of this approach, details regarding the shares can be set differently or globally in the [global] section, which enhances the structural transparency of the configuration file.

28.3.3.1 The global Section

The following parameters of the [global] section need some adjustment to match the requirements of your network setup so other machines can access your Samba server via SMB in a Windows environment.

workgroup = TUX-NET

This line assigns the Samba server to a workgroup. Replace TUX-NET with an appropriate workgroup of your networking environment. Your Samba server appears under its DNS name unless this name has been assigned to some other machine in the network. If the DNS name is not available, set the server name using netbiosname=MYNAME. For more details about this parameter, see the smb.conf man page.

os level = 20

This parameter triggers whether your Samba server tries to become LMB (local master browser) for its workgroup. With the Samba 3 release series, it is seldom necessary to override the default setting (20). Choose a very low value such as 2 to spare the existing Windows network from any disturbances caused by a misconfigured Samba server. More information about this important topic can be found in the Network Browsing chapter of the Samba 3 Howto; for more information on the Samba 3 Howto, see Section 28.7, “For More Information”.

If no other SMB server is present in your network (such as a Windows 2000 server) and you want the Samba server to keep a list of all systems present in the local environment, set the os level to a higher value (for example, 65). Your Samba server is then chosen as LMB for your local network.

When changing this setting, consider carefully how this could affect an existing Windows network environment. First test the changes in an isolated network or at a noncritical time of day.

wins support and wins server

To integrate your Samba server into an existing Windows network with an active WINS server, enable the wins server option and set its value to the IP address of that WINS server.

If your Windows machines are connected to separate subnets and need to still be aware of each other, you need to set up a WINS server. To turn a Samba server into such a WINS server, set the option wins support = Yes. Make sure that only one Samba server of the network has this setting enabled. The options wins server and wins support must never be enabled at the same time in your smb.conf file.

28.3.3.2 Shares

The following examples illustrate how a CD-ROM drive and the user directories (homes) are made available to the SMB clients.

[cdrom]

To avoid having the CD-ROM drive accidentally made available, these lines are deactivated with comment marks (semicolons in this case). Remove the semicolons in the first column to share the CD-ROM drive with Samba.

Example 28.1: A CD-ROM Share (deactivated)
;[cdrom]
;       comment = Linux CD-ROM
;       path = /media/cdrom
;       locking = No
[cdrom] and comment

The [cdrom] section entry is the name of the share that can be seen by all SMB clients on the network. An additional comment can be added to further describe the share.

path = /media/cdrom

path exports the directory /media/cdrom.

By means of a very restrictive default configuration, this kind of share is only made available to the users present on this system. If this share should be made available to everybody, add a line guest ok = yes to the configuration. This setting gives read permissions to anyone on the network. It is recommended to handle this parameter with great care. This applies even more to the use of this parameter in the [global] section.

[homes]

The [homes] share is of special importance here. If the user has a valid account and password for the Linux file server and his own home directory, he can be connected to it.

Example 28.2: [homes] Share
[homes]
	comment = Home Directories
	valid users = %S
	browseable = No
	read only = No
	create mask = 0640
	directory mask = 0750
[homes]

As long as there is no other share using the share name of the user connecting to the SMB server, a share is dynamically generated using the [homes] share directives. The resulting name of the share is the username.

valid users = %S

%S is replaced with the concrete name of the share as soon as a connection has been successfully established. For a [homes] share, this is always the username. As a consequence, access rights to a user's share are restricted exclusively to that user.

browseable = No

This setting makes the share invisible in the network environment.

read only = No

By default, Samba prohibits write access to any exported share by means of the read only = Yes parameter. To make a share writable, set the value read only = No, which is synonymous with writable = Yes.

create mask = 0640

Systems that are not based on MS Windows NT do not understand the concept of UNIX permissions, so they cannot assign permissions when creating a file. The parameter create mask defines the access permissions assigned to newly created files. This only applies to writable shares. In effect, this setting means the owner has read and write permissions and the members of the owner's primary group have read permissions. valid users = %S prevents read access even if the group has read permissions. For the group to have read or write access, deactivate the line valid users = %S.

28.3.3.3 Security Levels

To improve security, each share access can be protected with a password. SMB offers the following ways of checking permissions:

Share Level Security (security = share)

A password is firmly assigned to a share. Everyone who knows this password has access to that share.

User Level Security (security = user)

This variant introduces the concept of the user to SMB. Each user must register with the server with his or her own password. After registration, the server can grant access to individual exported shares dependent on usernames.

Server Level Security (security = server)

To its clients, Samba pretends to be working in user level mode. However, it passes all password queries to another user level mode server, which takes care of authentication. This setting requires the additional password server parameter.

ADS Level Security (security = ADS)

In this mode, Samba will act as a domain member in an Active Directory environment. To operate in this mode, the machine running Samba needs Kerberos installed and configured. You must join the machine using Samba to the ADS realm. This can be done using the YaST Windows Domain Membership module.

Domain Level Security (security = domain)

This mode will only work correctly if the machine has been joined into a Windows NT Domain. Samba will try to validate username and password by passing it to a Windows NT Primary or Backup Domain Controller. The same way as a Windows NT Server would do. It expects the encrypted passwords parameter to be set to yes.

The selection of share, user, server, or domain level security applies to the entire server. It is not possible to offer individual shares of a server configuration with share level security and others with user level security. However, you can run a separate Samba server for each configured IP address on a system.

More information about this subject can be found in the Samba 3 HOWTO. For multiple servers on one system, pay attention to the options interfaces and bind interfaces only.

28.4 Configuring Clients

Clients can only access the Samba server via TCP/IP. NetBEUI and NetBIOS via IPX cannot be used with Samba.

28.4.1 Configuring a Samba Client with YaST

Configure a Samba client to access resources (files or printers) on the Samba or Windows server. Enter the NT or Active Directory domain or workgroup in the dialog Network Services › Windows Domain Membership. If you activate Also Use SMB Information for Linux Authentication, the user authentication runs over the Samba, NT or Kerberos server.

Click Expert Settings for advanced configuration options. For example, use the Mount Server Directories table to enable mounting server home directory automatically with authentication. This way users will be able to access their home directories when hosted on CIFS. For details, see the the pam_mount man page.

After completing all settings, confirm the dialog to finish the configuration.

28.5 Samba as Login Server

In networks where predominantly Windows clients are found, it is often preferable that users may only register with a valid account and password. In a Windows-based network, this task is handled by a primary domain controller (PDC). You can use a Windows NT server configured as PDC, but this task can also be done with a Samba server. The entries that must be made in the [global] section of smb.conf are shown in Example 28.3, “Global Section in smb.conf”.

Example 28.3: Global Section in smb.conf
[global]
    workgroup = TUX-NET
    domain logons = Yes
    domain master = Yes

If encrypted passwords are used for verification purposes the Samba server must be able to handle these. The entry encrypt passwords = yes in the [global] section enables this (with Samba version 3, this is now the default). In addition, it is necessary to prepare user accounts and passwords in an encryption format that conforms with Windows. Do this with the command smbpasswd -a name. Create the domain account for the computers, required by the Windows domain concept, with the following commands:

useradd hostname\$
smbpasswd -a -m hostname

With the useradd command, a dollar sign is added. The command smbpasswd inserts this automatically when the parameter -m is used. The commented configuration example (/usr/share/doc/packages/samba/examples/smb.conf.SUSE) contains settings that automate this task.

add machine script = /usr/sbin/useradd -g nogroup -c "NT Machine Account" \
-s /bin/false %m\$

To make sure that Samba can execute this script correctly, choose a Samba user with the required administrator permissions and add it to the ntadmin group. Then all users belonging to this Linux group can be assigned Domain Admin status with the command:

net groupmap add ntgroup="Domain Admins" unixgroup=ntadmin

For more information about this topic, see Chapter 12 of the Samba 3 HOWTO, found in /usr/share/doc/packages/samba/Samba3-HOWTO.pdf.

28.6 Samba Server in the Network with Active Directory

If you run Linux servers and Windows servers together, you can build two independent authentication systems and networks or connect servers to one network with one central authentication system. Because Samba can cooperate with an active directory domain, you can join your SUSE Linux Enterprise Server to Active Directory (AD).

Join an existing AD domain during installation or by later activating SMB user authentication with YaST in the installed system. Domain join during installation is covered in Section 6.16.1.7, “User Authentication Method”.

To join an AD domain in a running system, proceed as follows:

  1. Log in as root and start YaST.

  2. Start Network Services › Windows Domain Membership.

  3. Enter the domain to join at Domain or Workgroup in the Windows Domain Membership screen.

    Determining Windows Domain Membership
    Figure 28.1: Determining Windows Domain Membership
  4. Check Also Use SMB Information for Linux Authentication to use the SMB source for Linux authentication on your SUSE Linux Enterprise Server.

  5. Click OK and confirm the domain join when prompted for it.

  6. Provide the password for the Windows Administrator on the AD server and click OK.

    Your server is now set up to pull in all authentication data from the Active Directory domain controller.

Tip
Tip

In an environment with more than one Samba server, UIDs and GIDs will not be created consistently. The UIDs that get assigned to users will be dependent on the order in which they first log in, which results in UID conflicts across servers. To fix this, you need to make use of idnetity mapping. See https://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/idmapper.html for more details

28.7 For More Information

Detailed Samba information is available in the digital documentation. Enter apropos samba at the command line to display some manual pages or just browse the /usr/share/doc/packages/samba directory if Samba documentation is installed for more online documentation and examples. Find a commented example configuration (smb.conf.SUSE) in the examples subdirectory.

The Samba 3 HOWTO provided by the Samba team includes a section about troubleshooting. In addition to that, Part V of the document provides a step-by-step guide to checking your configuration. You can find Samba 3 HOWTO in /usr/share/doc/packages/samba/Samba3-HOWTO.pdf after installing the package samba-doc.

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