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Applies to SUSE Linux Enterprise Desktop 15 SP1

33 Samba Edit source

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

33.1 Terminology Edit source

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.

CIFS protocol

The CIFS (common Internet file system) protocol, also known as SMB1 is an early version of the SMB protocol. 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. In recent versions of Samba, it is disabled by default for security reasons.

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 called 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 host names 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. Common operating systems, such as Windows and macOS 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 need 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 a domain. For data replication, additional domain controllers are available in one domain.

33.2 Installing a Samba Server Edit source

Installing a Samba server is not supported on SUSE Linux Enterprise Desktop. For information about installing and configuring a Samba server, see Administration Guide for SUSE Linux Enterprise Server.

33.3 Configuring Clients Edit source

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

33.3.1 Configuring a Samba Client with YaST Edit source

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 can access their home directories when hosted on CIFS. For details, see the pam_mount man page.

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

33.3.2 Mounting SMB1/CIFS Shares on Clients Edit source

The first version of the SMB network protocol, SMB1 or CIFS, is an old and insecure protocol which has been deprecated by its originator, Microsoft. For security reasons, the mount command on SUSE Linux Enterprise Desktop will only mount SMB shares using newer protocol versions by default, namely SMB 2.1, SMB 3.0, or SMB 3.02.

However, this change only affects mount and mounting via /etc/fstab. SMB1 is still available by explicitly requiring it. Use the following command:

  • The smbclient tool.

  • The Samba server software shipped with SUSE Linux Enterprise Server.

There are setups in which this default setting will lead to connection failures, because only SMB1 can be used:

  • Setups using an SMB server that does not support newer SMB protocol versions. Windows has offered SMB 2.1 support since Windows 7 and Windows Server 2008.

  • Setups that rely on SMB1's/CIFS's Unix extensions. These extensions have not been ported to newer protocol versions.

Important
Important: Decreased System Security

Following the instruction below makes it possible to exploit security issues. For more information about the issues, see https://blogs.technet.microsoft.com/filecab/2016/09/16/stop-using-smb1/.

As soon as possible, upgrade your server to allow for a more secure SMB version.

If you need to enable SMB1 shares on the current SUSE Linux Enterprise Desktop kernel, add the option vers=1.0 to the mount command line you use:

root # mount -t cifs //HOST/SHARE /MOUNT_POINT –o username=USER_ID,vers=1.0

Alternatively, you can enable SMB1 shares globally within your SUSE Linux Enterprise Desktop installation. To do so, add the following to /etc/samba/smb.conf under the section [global]:

        client min protocol = CORE

33.4 Samba as Login Server Edit source

In enterprise settings, it is often desirable to allow access only to users registered on a central instance. 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 33.1, “Global Section in smb.conf”.

Example 33.1: Global Section in smb.conf
[global]
    workgroup = WORKGROUP
    domain logons = Yes
    domain master = Yes

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

33.5 Advanced Topics Edit source

This section introduces more advanced techniques to manage both the client and server part of the Samba suite.

33.5.1 Transparent File Compression on Btrfs Edit source

Samba allows clients to remotely manipulate file and directory compression flags for shares placed on the Btrfs file system. Windows Explorer provides the ability to flag files/directories for transparent compression via the File › Properties › Advanced dialog:

Windows Explorer Advanced Attributes Dialog
Figure 33.1: Windows Explorer Advanced Attributes Dialog

Files flagged for compression are transparently compressed and decompressed by the underlying file system when accessed or modified. This normally results in storage capacity savings at the expense of extra CPU overhead when accessing the file. New files and directories inherit the compression flag from the parent directory, unless created with the FILE_NO_COMPRESSION option.

Windows Explorer presents compressed files and directories visually differently to those that are not compressed:

Windows Explorer Directory Listing with Compressed Files
Figure 33.2: Windows Explorer Directory Listing with Compressed Files

You can enable Samba share compression either manually by adding

vfs objects = btrfs

to the share configuration in /etc/samba/smb.conf, or using YaST: Network Services › Samba Server › Add, and checking Utilize Btrfs Features.

33.5.2 Snapshots Edit source

Snapshots, also called Shadow Copies, are copies of the state of a file system subvolume at a certain point of time. Snapper is the tool to manage these snapshots in Linux. Snapshots are supported on the Btrfs file system or thinly-provisioned LVM volumes. The Samba suite supports managing remote snapshots through the FSRVP protocol on both the server and client side.

33.5.2.1 Previous Versions Edit source

Snapshots on a Samba server can be exposed to remote Windows clients as file or directory previous versions.

To enable snapshots on a Samba server, the following conditions must be fulfilled:

  • The SMB network share resides on a Btrfs subvolume.

  • The SMB network share path has a related snapper configuration file. You can create the snapper file with

    tux > sudo snapper -c <cfg_name> create-config /path/to/share

    For more information on snapper, see Chapter 7, System Recovery and Snapshot Management with Snapper.

  • The snapshot directory tree must allow access for relevant users. For more information, see the PERMISSIONS section of the vfs_snapper manual page (man 8 vfs_snapper).

To support remote snapshots, you need to modify the /etc/samba/smb.conf file. You can do it either with YaST › Network Services › Samba Server, or manually by enhancing the relevant share section with

vfs objects = snapper

Note that you need to restart the Samba service for manual smb.conf changes to take effect:

tux > sudo systemctl restart nmb smb
Adding a New Samba Share with Snapshotting Enabled
Figure 33.3: Adding a New Samba Share with Snapshotting Enabled

After being configured, snapshots created by snapper for the Samba share path can be accessed from Windows Explorer from a file or directory's Previous Versions tab.

The Previous Versions tab in Windows Explorer
Figure 33.4: The Previous Versions tab in Windows Explorer

33.5.2.2 Remote Share Snapshots Edit source

By default, snapshots can only be created and deleted on the Samba server locally, via the snapper command line utility, or using snapper's time line feature.

Samba can be configured to process share snapshot creation and deletion requests from remote hosts using the File Server Remote VSS Protocol (FSRVP).

In addition to the configuration and prerequisites documented in Section 33.5.2.1, “Previous Versions”, the following global configuration is required in /etc/samba/smb.conf:

[global]
rpc_daemon:fssd = fork
registry shares = yes
include = registry

FSRVP clients, including Samba's rpcclient and Windows Server 2012 DiskShadow.exe, can then instruct Samba to create or delete a snapshot for a given share, and expose the snapshot as a new share.

33.5.2.3 Managing Snapshots Remotely from Linux with rpcclient Edit source

The samba-client package contains an FSRVP client that can remotely request a Windows/Samba server to create and expose a snapshot of a given share. You can then use existing tools in SUSE Linux Enterprise Desktop to mount the exposed share and back up its files. Requests to the server are sent using the rpcclient binary.

Example 33.2: Using rpcclient to Request a Windows Server 2012 Share Snapshot

Connect to win-server.example.com server as an administrator in an EXAMPLE domain:

root # rpcclient -U 'EXAMPLE\Administrator' ncacn_np:win-server.example.com[ndr64,sign]
Enter EXAMPLE/Administrator's password:

Check that the SMB share is visible for rpcclient:

root # rpcclient $> netshareenum
netname: windows_server_2012_share
remark:
path:   C:\Shares\windows_server_2012_share
password:       (null)

Check that the SMB share supports snapshot creation:

root # rpcclient $> fss_is_path_sup windows_server_2012_share \
UNC \\WIN-SERVER\windows_server_2012_share\ supports shadow copy requests

Request the creation of a share snapshot:

root # rpcclient $> fss_create_expose backup ro windows_server_2012_share
13fe880e-e232-493d-87e9-402f21019fb6: shadow-copy set created
13fe880e-e232-493d-87e9-402f21019fb6(1c26544e-8251-445f-be89-d1e0a3938777): \
\\WIN-SERVER\windows_server_2012_share\ shadow-copy added to set
13fe880e-e232-493d-87e9-402f21019fb6: prepare completed in 0 secs
13fe880e-e232-493d-87e9-402f21019fb6: commit completed in 1 secs
13fe880e-e232-493d-87e9-402f21019fb6(1c26544e-8251-445f-be89-d1e0a3938777): \
share windows_server_2012_share@{1C26544E-8251-445F-BE89-D1E0A3938777} \
exposed as a snapshot of \\WIN-SERVER\windows_server_2012_share\

Confirm that the snapshot share is exposed by the server:

root # rpcclient $> netshareenum
netname: windows_server_2012_share
remark:
path:   C:\Shares\windows_server_2012_share
password:       (null)

netname: windows_server_2012_share@{1C26544E-8251-445F-BE89-D1E0A3938777}
remark: (null)
path:   \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy{F6E6507E-F537-11E3-9404-B8AC6F927453}\Shares\windows_server_2012_share\
password:       (null)

Attempt to delete the snapshot share:

root # rpcclient $> fss_delete windows_server_2012_share \
13fe880e-e232-493d-87e9-402f21019fb6 1c26544e-8251-445f-be89-d1e0a3938777
13fe880e-e232-493d-87e9-402f21019fb6(1c26544e-8251-445f-be89-d1e0a3938777): \
\\WIN-SERVER\windows_server_2012_share\ shadow-copy deleted

Confirm that the snapshot share has been removed by the server:

root # rpcclient $> netshareenum
netname: windows_server_2012_share
remark:
path:   C:\Shares\windows_server_2012_share
password:       (null)

33.5.2.4 Managing Snapshots Remotely from Windows with DiskShadow.exe Edit source

You can manage snapshots of SMB shares on the Linux Samba server from the Windows environment acting as a client as well. Windows Server 2012 includes the DiskShadow.exe utility that can manage remote shares similar to the rpcclient described in Section 33.5.2.3, “Managing Snapshots Remotely from Linux with rpcclient. Note that you need to carefully set up the Samba server first.

Following is an example procedure to set up the Samba server so that the Windows Server client can manage its share's snapshots. Note that EXAMPLE is the Active Directory domain used in the testing environment, fsrvp-server.example.com is the host name of the Samba server, and /srv/smb is the path to the SMB share.

Procedure 33.1: Detailed Samba Server Configuration
  1. Join Active Directory domain via YaST.

  2. Ensure that the Active Domain DNS entry was correct:

    fsrvp-server:~ # net -U 'Administrator' ads dns register \
    fsrvp-server.example.com <IP address>
    Successfully registered hostname with DNS
  3. Create Btrfs subvolume at /srv/smb

    fsrvp-server:~ # btrfs subvolume create /srv/smb
  4. Create snapper configuration file for path /srv/smb

    fsrvp-server:~ # snapper -c <snapper_config> create-config /srv/smb
  5. Create new share with path /srv/smb, and YaST Expose Snapshots check box enabled. Make sure to add the following snippets to the global section of /etc/samba/smb.conf as mentioned in Section 33.5.2.2, “Remote Share Snapshots”:

    [global]
     rpc_daemon:fssd = fork
     registry shares = yes
     include = registry
  6. Restart Samba with systemctl restart nmb smb

  7. Configure snapper permissions:

    fsrvp-server:~ # snapper -c <snapper_config> set-config \
    ALLOW_USERS="EXAMPLE\\\\Administrator EXAMPLE\\\\win-client$"

    Ensure that any ALLOW_USERS are also permitted traversal of the .snapshots subdirectory.

    fsrvp-server:~ # snapper -c <snapper_config> set-config SYNC_ACL=yes
    Important
    Important: Path Escaping

    Be careful about the '\' escapes! Escape twice to ensure that the value stored in /etc/snapper/configs/<snapper_config> is escaped once.

    "EXAMPLE\win-client$" corresponds to the Windows client computer account. Windows issues initial FSRVP requests while authenticated with this account.

  8. Grant Windows client account necessary privileges:

    fsrvp-server:~ # net -U 'Administrator' rpc rights grant \
    "EXAMPLE\\win-client$" SeBackupPrivilege
    Successfully granted rights.

    The previous command is not needed for the "EXAMPLE\Administrator" user, which has privileges already granted.

Procedure 33.2: Windows Client Setup and DiskShadow.exe in Action
  1. Boot Windows Server 2012 (example host name WIN-CLIENT).

  2. Join the same Active Directory domain EXAMPLE as with the SUSE Linux Enterprise Desktop.

  3. Reboot.

  4. Open Powershell.

  5. Start DiskShadow.exe and begin the backup procedure:

    PS C:\Users\Administrator.EXAMPLE> diskshadow.exe
    Microsoft DiskShadow version 1.0
    Copyright (C) 2012 Microsoft Corporation
    On computer:  WIN-CLIENT,  6/17/2014 3:53:54 PM
    
    DISKSHADOW> begin backup
  6. Specify that shadow copy persists across program exit, reset or reboot:

    DISKSHADOW> set context PERSISTENT
  7. Check whether the specified share supports snapshots, and create one:

    DISKSHADOW> add volume \\fsrvp-server\sles_snapper
    
    DISKSHADOW> create
    Alias VSS_SHADOW_1 for shadow ID {de4ddca4-4978-4805-8776-cdf82d190a4a} set as \
     environment variable.
    Alias VSS_SHADOW_SET for shadow set ID {c58e1452-c554-400e-a266-d11d5c837cb1} \
     set as environment variable.
    
    Querying all shadow copies with the shadow copy set ID \
     {c58e1452-c554-400e-a266-d11d5c837cb1}
    
     * Shadow copy ID = {de4ddca4-4978-4805-8776-cdf82d190a4a}     %VSS_SHADOW_1%
        - Shadow copy set: {c58e1452-c554-400e-a266-d11d5c837cb1}  %VSS_SHADOW_SET%
        - Original count of shadow copies = 1
        - Original volume name: \\FSRVP-SERVER\SLES_SNAPPER\ \
          [volume not on this machine]
        - Creation time: 6/17/2014 3:54:43 PM
        - Shadow copy device name:
          \\FSRVP-SERVER\SLES_SNAPPER@{31afd84a-44a7-41be-b9b0-751898756faa}
        - Originating machine: FSRVP-SERVER
        - Service machine: win-client.example.com
        - Not exposed
        - Provider ID: {89300202-3cec-4981-9171-19f59559e0f2}
        - Attributes:  No_Auto_Release Persistent FileShare
    
    Number of shadow copies listed: 1
  8. Finish the backup procedure:

    DISKSHADOW> end backup
  9. After the snapshot was created, try to delete it and verify the deletion:

    DISKSHADOW> delete shadows volume \\FSRVP-SERVER\SLES_SNAPPER\
    Deleting shadow copy {de4ddca4-4978-4805-8776-cdf82d190a4a} on volume \
     \\FSRVP-SERVER\SLES_SNAPPER\ from provider \
    {89300202-3cec-4981-9171-19f59559e0f2} [Attributes: 0x04000009]...
    
    Number of shadow copies deleted: 1
    
    DISKSHADOW> list shadows all
    
    Querying all shadow copies on the computer ...
    No shadow copies found in system.

33.6 For More Information Edit source

  • Man Pages:  To see a list of all man pages installed with the package samba, run apropos samba. Open any of the man pages with man NAME_OF_MAN_PAGE.

  • SUSE-specific README file:  The package samba-client contains the file /usr/share/doc/packages/samba/README.SUSE.

  • Additional Packaged Documentation:  Install the package samba-doc with zypper install samba-doc.

    This documentation installs into /usr/share/doc/packages/samba. It contains an HTML version of the man pages and a library of example configurations (such as smb.conf.SUSE).

  • Online Documentation:  The Samba wiki contains extensive User Documentation at https://wiki.samba.org/index.php/User_Documentation.

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