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File and Record Locking"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 13. File, Directory and Share Access Controls</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="groupmapping.html">Prev</a> </td><th width="60%" align="center">Part III. Advanced Configuration</th><td width="20%" align="right"> <a accesskey="n" href="locking.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="AccessControls"></a>Chapter 13. File, Directory and Share Access Controls</h2></div><div><div class="author"><h3 class="author"><span class="firstname">John</span> <span class="othername">H.</span> <span class="surname">Terpstra</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><tt class="email"><<a href="mailto:jht@samba.org">jht@samba.org</a>></tt></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Jeremy</span> <span class="surname">Allison</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><tt class="email"><<a href="mailto:jra@samba.org">jra@samba.org</a>></tt></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Jelmer</span> <span class="othername">R.</span> <span class="surname">Vernooij</span></h3><span class="contrib">drawing</span><div class="affiliation"><span class="orgname">The Samba Team<br></span><div class="address"><p><tt class="email"><<a href="mailto:jelmer@samba.org">jelmer@samba.org</a>></tt></p></div></div></div></div><div><p class="pubdate">May 10, 2003</p></div></div><div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="AccessControls.html#id2911341">Features and Benefits</a></dt><dt><a href="AccessControls.html#id2911525">File System Access Controls</a></dt><dd><dl><dt><a href="AccessControls.html#id2911543">MS Windows NTFS Comparison with UNIX File Systems</a></dt><dt><a href="AccessControls.html#id2911956">Managing Directories</a></dt><dt><a href="AccessControls.html#id2912050">File and Directory Access Control</a></dt></dl></dd><dt><a href="AccessControls.html#id2912290">Share Definition Access Controls</a></dt><dd><dl><dt><a href="AccessControls.html#id2912329">User and Group-Based Controls</a></dt><dt><a href="AccessControls.html#id2912779">File and Directory Permissions-Based Controls</a></dt><dt><a href="AccessControls.html#id2913187">Miscellaneous Controls</a></dt></dl></dd><dt><a href="AccessControls.html#id2913585">Access Controls on Shares</a></dt><dd><dl><dt><a href="AccessControls.html#id2913670">Share Permissions Management</a></dt></dl></dd><dt><a href="AccessControls.html#id2913978">MS Windows Access Control Lists and UNIX Interoperability</a></dt><dd><dl><dt><a href="AccessControls.html#id2913986">Managing UNIX Permissions Using NT Security Dialogs</a></dt><dt><a href="AccessControls.html#id2914042">Viewing File Security on a Samba Share</a></dt><dt><a href="AccessControls.html#id2914124">Viewing File Ownership</a></dt><dt><a href="AccessControls.html#id2914264">Viewing File or Directory Permissions</a></dt><dt><a href="AccessControls.html#id2914515">Modifying File or Directory Permissions</a></dt><dt><a href="AccessControls.html#id2914698">Interaction with the Standard Samba create mask Parameters</a></dt><dt><a href="AccessControls.html#id2915106">Interaction with the Standard Samba File Attribute Mapping</a></dt></dl></dd><dt><a href="AccessControls.html#id2915195">Common Errors</a></dt><dd><dl><dt><a href="AccessControls.html#id2915209">Users Cannot Write to a Public Share</a></dt><dt><a href="AccessControls.html#id2915635">File Operations Done as root with force user Set</a></dt><dt><a href="AccessControls.html#id2915690">MS Word with Samba Changes Owner of File</a></dt></dl></dd></dl></div><p> -<a class="indexterm" name="id2911255"></a> -Advanced MS Windows users are frequently perplexed when file, directory and share manipulation of -resources shared via Samba do not behave in the manner they might expect. MS Windows network -administrators are often confused regarding network access controls and how to -provide users with the access they need while protecting resources from unauthorized access. -</p><p> -Many UNIX administrators are unfamiliar with the MS Windows environment and in particular -have difficulty in visualizing what the MS Windows user wishes to achieve in attempts to set file -and directory access permissions. -</p><p> -The problem lies in the differences in how file and directory permissions and controls work -between the two environments. This difference is one that Samba cannot completely hide, even -though it does try to bridge the chasm to a degree. -</p><p> -<a class="indexterm" name="id2911291"></a> -<a class="indexterm" name="id2911300"></a> - -POSIX Access Control List technology has been available (along with Extended Attributes) -for UNIX for many years, yet there is little evidence today of any significant use. This -explains to some extent the slow adoption of ACLs into commercial Linux products. MS Windows -administrators are astounded at this, given that ACLs were a foundational capability of the now -decade-old MS Windows NT operating system. -</p><p> -The purpose of this chapter is to present each of the points of control that are possible with -Samba-3 in the hope that this will help the network administrator to find the optimum method -for delivering the best environment for MS Windows desktop users. -</p><p> -This is an opportune point to mention that Samba was created to provide a means of interoperability -and interchange of data between differing operating environments. Samba has no intent to change -UNIX/Linux into a platform like MS Windows. Instead the purpose was and is to provide a sufficient -level of exchange of data between the two environments. What is available today extends well -beyond early plans and expectations, yet the gap continues to shrink. -</p><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2911341"></a>Features and Benefits</h2></div></div><div></div></div><p> - Samba offers a lot of flexibility in file system access management. These are the key access control - facilities present in Samba today: - </p><div class="itemizedlist"><p class="title"><b>Samba Access Control Facilities</b></p><ul type="disc"><li><p> - <a class="indexterm" name="id2911368"></a> - <span class="emphasis"><em>UNIX File and Directory Permissions</em></span> - </p><p> - Samba honors and implements UNIX file system access controls. Users - who access a Samba server will do so as a particular MS Windows user. - This information is passed to the Samba server as part of the logon or - connection setup process. Samba uses this user identity to validate - whether or not the user should be given access to file system resources - (files and directories). This chapter provides an overview for those - to whom the UNIX permissions and controls are a little strange or unknown. - </p></li><li><p> - <span class="emphasis"><em>Samba Share Definitions</em></span> - </p><p> - In configuring share settings and controls in the <tt class="filename">smb.conf</tt> file, - the network administrator can exercise overrides to native file - system permissions and behaviors. This can be handy and convenient - to effect behavior that is more like what MS Windows NT users expect - but it is seldom the <span class="emphasis"><em>best</em></span> way to achieve this. - The basic options and techniques are described herein. - </p></li><li><p> - <span class="emphasis"><em>Samba Share ACLs</em></span> - <a class="indexterm" name="id2911453"></a> - </p><p> - Just like it is possible in MS Windows NT to set ACLs on shares - themselves, so it is possible to do this in Samba. - Few people make use of this facility, yet it remains on of the - easiest ways to affect access controls (restrictions) and can often - do so with minimum invasiveness compared with other methods. - </p></li><li><p> - <a class="indexterm" name="id2911481"></a> - <a class="indexterm" name="id2911492"></a> - <span class="emphasis"><em>MS Windows ACLs through UNIX POSIX ACLs</em></span> - </p><p> - The use of POSIX ACLs on UNIX/Linux is possible only if the underlying - operating system supports them. If not, then this option will not be - available to you. Current UNIX technology platforms have native support - for POSIX ACLs. There are patches for the Linux kernel that also provide - this. Sadly, few Linux platforms ship today with native ACLs and - Extended Attributes enabled. This chapter has pertinent information - for users of platforms that support them. - </p></li></ul></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2911525"></a>File System Access Controls</h2></div></div><div></div></div><p> -Perhaps the most important recognition to be made is the simple fact that MS Windows NT4/200x/XP -implement a totally divergent file system technology from what is provided in the UNIX operating system -environment. First we consider what the most significant differences are, then we look -at how Samba helps to bridge the differences. -</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2911543"></a>MS Windows NTFS Comparison with UNIX File Systems</h3></div></div><div></div></div><p> -<a class="indexterm" name="id2911555"></a> -<a class="indexterm" name="id2911563"></a> -<a class="indexterm" name="id2911571"></a> -<a class="indexterm" name="id2911582"></a> - - Samba operates on top of the UNIX file system. This means it is subject to UNIX file system conventions - and permissions. It also means that if the MS Windows networking environment requires file system - behavior that differs from UNIX file system behavior then somehow Samba is responsible for emulating - that in a transparent and consistent manner. - </p><p> - It is good news that Samba does this to a large extent and on top of that provides a high degree - of optional configuration to override the default behavior. We look at some of these over-rides, - but for the greater part we will stay within the bounds of default behavior. Those wishing to explore - the depths of control ability should review the <tt class="filename">smb.conf</tt> man page. - </p><p>The following compares file system features for UNIX with those of Microsoft Windows NT/200x: - <a class="indexterm" name="id2911624"></a> - - </p><div class="variablelist"><dl><dt><span class="term">Name Space</span></dt><dd><p> - MS Windows NT4/200x/XP files names may be up to 254 characters long, and UNIX file names - may be 1023 characters long. In MS Windows, file extensions indicate particular file types, - in UNIX this is not so rigorously observed as all names are considered arbitrary. - </p><p> - What MS Windows calls a folder, UNIX calls a directory. - </p></dd><dt><span class="term">Case Sensitivity</span></dt><dd><p> - <a class="indexterm" name="id2911680"></a> - <a class="indexterm" name="id2911689"></a> - MS Windows file names are generally upper case if made up of 8.3 (8 character file name - and 3 character extension. File names that are longer than 8.3 are case preserving and case - insensitive. - </p><p> - UNIX file and directory names are case sensitive and case preserving. Samba implements the - MS Windows file name behavior, but it does so as a user application. The UNIX file system - provides no mechanism to perform case insensitive file name lookups. MS Windows does this - by default. This means that Samba has to carry the processing overhead to provide features - that are not native to the UNIX operating system environment. - </p><p> - Consider the following. All are unique UNIX names but one single MS Windows file name: - </p><pre class="screen"> - MYFILE.TXT - MyFile.txt - myfile.txt - </pre><p> - So clearly, in an MS Windows file name space these three files cannot co-exist, but in UNIX - they can. - </p><p> - So what should Samba do if all three are present? That which is lexically first will be - accessible to MS Windows users, the others are invisible and unaccessible any - other solution would be suicidal. - </p></dd><dt><span class="term">Directory Separators</span></dt><dd><p> - <a class="indexterm" name="id2911762"></a> - MS Windows and DOS uses the backslash <tt class="constant">\</tt> as a directory delimiter, and UNIX uses - the forward-slash <tt class="constant">/</tt> as its directory delimiter. This is handled transparently by Samba. - </p></dd><dt><span class="term">Drive Identification</span></dt><dd><p> - <a class="indexterm" name="id2911799"></a> - MS Windows products support a notion of drive letters, like <b class="command">C:</b> to represent - disk partitions. UNIX has no concept of separate identifiers for file partitions, each - such file system is mounted to become part of the overall directory tree. - The UNIX directory tree begins at <tt class="constant">/</tt> just like the root of a DOS drive is specified as - <tt class="constant">C:\</tt>. - </p></dd><dt><span class="term">File Naming Conventions</span></dt><dd><p> - <a class="indexterm" name="id2911846"></a> - MS Windows generally never experiences file names that begin with a dot (<tt class="constant">.</tt>) while in UNIX these - are commonly found in a user's home directory. Files that begin with a dot (<tt class="constant">.</tt>) are typically - either start-up files for various UNIX applications, or they may be files that contain - start-up configuration data. - </p></dd><dt><span class="term">Links and Short-Cuts</span></dt><dd><p> - <a class="indexterm" name="id2911886"></a> - <a class="indexterm" name="id2911897"></a> - <a class="indexterm" name="id2911908"></a> - MS Windows make use of “<span class="quote">links and short-cuts</span>” that are actually special types of files that will - redirect an attempt to execute the file to the real location of the file. UNIX knows of file and directory - links, but they are entirely different from what MS Windows users are used to. - </p><p> - Symbolic links are files in UNIX that contain the actual location of the data (file or directory). An - operation (like read or write) will operate directly on the file referenced. Symbolic links are also - referred to as “<span class="quote">soft links.</span>” A hard link is something that MS Windows is not familiar with. It allows - one physical file to be known simultaneously by more than one file name. - </p></dd></dl></div><p> - There are many other subtle differences that may cause the MS Windows administrator some temporary discomfort - in the process of becoming familiar with UNIX/Linux. These are best left for a text that is dedicated to the - purpose of UNIX/Linux training and education. - </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2911956"></a>Managing Directories</h3></div></div><div></div></div><p> - There are three basic operations for managing directories: <b class="command">create, delete, rename</b>. - </p><div class="table"><a name="id2911975"></a><p class="title"><b>Table 13.1. Managing Directories with UNIX and Windows</b></p><table summary="Managing Directories with UNIX and Windows" border="1"><colgroup><col><col><col></colgroup><thead><tr><th align="center">Action</th><th align="center">MS Windows Command</th><th align="center">UNIX Command</th></tr></thead><tbody><tr><td align="center">create</td><td align="center">md folder</td><td align="center">mkdir folder</td></tr><tr><td align="center">delete</td><td align="center">rd folder</td><td align="center">rmdir folder</td></tr><tr><td align="center">rename</td><td align="center">rename oldname newname</td><td align="center">mv oldname newname</td></tr></tbody></table></div><p> - </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2912050"></a>File and Directory Access Control</h3></div></div><div></div></div><p> - <a class="indexterm" name="id2912062"></a> - The network administrator is strongly advised to read foundational training manuals and reference materials - regarding file and directory permissions maintenance. Much can be achieved with the basic UNIX permissions - without having to resort to more complex facilities like POSIX Access Control Lists (ACLs) or Extended - Attributes (EAs). - </p><p> - UNIX/Linux file and directory access permissions involves setting three primary sets of data and one control set. - A UNIX file listing looks as follows: -</p><pre class="screen"> -<tt class="prompt">$ </tt><b class="userinput"><tt>ls -la</tt></b> -total 632 -drwxr-xr-x 13 maryo gnomes 816 2003-05-12 22:56 . -drwxrwxr-x 37 maryo gnomes 3800 2003-05-12 22:29 .. -dr-xr-xr-x 2 maryo gnomes 48 2003-05-12 22:29 muchado02 -drwxrwxrwx 2 maryo gnomes 48 2003-05-12 22:29 muchado03 -drw-rw-rw- 2 maryo gnomes 48 2003-05-12 22:29 muchado04 -d-w--w--w- 2 maryo gnomes 48 2003-05-12 22:29 muchado05 -dr--r--r-- 2 maryo gnomes 48 2003-05-12 22:29 muchado06 -drwsrwsrwx 2 maryo gnomes 48 2003-05-12 22:29 muchado08 ----------- 1 maryo gnomes 1242 2003-05-12 22:31 mydata00.lst ---w--w--w- 1 maryo gnomes 7754 2003-05-12 22:33 mydata02.lst --r--r--r-- 1 maryo gnomes 21017 2003-05-12 22:32 mydata04.lst --rw-rw-rw- 1 maryo gnomes 41105 2003-05-12 22:32 mydata06.lst -<tt class="prompt">$ </tt> -</pre><p> - </p><p> - The columns above represent (from left to right): permissions, number of hard links to file, owner, group, size (bytes), access date, access time, file name. - </p><p> - An overview of the permissions field can be found in <link linkend="access1">. - </p><div class="figure"><a name="access1"></a><p class="title"><b>Figure 13.1. Overview of UNIX permissions field.</b></p><div class="mediaobject"><img src="projdoc/imagefiles/access1.png" width="270" alt="Overview of UNIX permissions field."></div></div><p> - Any bit flag may be unset. An unset bit flag is the equivalent of “<span class="quote">cannot</span>” and is represented as a “<span class="quote">-</span>” character. - - </p><div class="example"><a name="id2912202"></a><p class="title"><b>Example 13.1. Example File</b></p><pre class="programlisting"> - -rwxr-x--- Means: The owner (user) can read, write, execute - the group can read and execute - everyone else cannot do anything with it. - </pre></div><p> - - </p><p> - Additional possibilities in the [type] field are: c = character device, b = block device, p = pipe device, s = UNIX Domain Socket. - </p><p> - The letters <tt class="constant">rwxXst</tt> set permissions for the user, group and others as: read (r), write (w), execute (or access for directories) (x), - execute only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), - sticky (t). - </p><p> - When the sticky bit is set on a directory, files in that directory may be unlinked (deleted) or renamed only by root or their owner. - Without the sticky bit, anyone able to write to the directory can delete or rename files. The sticky bit is commonly found on - directories, such as <tt class="filename">/tmp</tt>, that are world-writable. - </p><p> - When the set user or group ID bit (s) is set on a directory, then all files created within it will be owned by the user and/or - group whose `set user or group' bit is set. This can be helpful in setting up directories for which it is desired that - all users who are in a group should be able to write to and read from a file, particularly when it is undesirable for that file - to be exclusively owned by a user whose primary group is not the group that all such users belong to. - </p><p> - When a directory is set <tt class="constant">drw-r-----</tt> this means that the owner can read and create (write) files in it, but because - the (x) execute flags are not set, files cannot be listed (seen) in the directory by anyone. The group can read files in the - directory but cannot create new files. If files in the directory are set to be readable and writable for the group, then - group members will be able to write to (or delete) them. - </p></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2912290"></a>Share Definition Access Controls</h2></div></div><div></div></div><p> -<a class="indexterm" name="id2912301"></a> -The following parameters in the <tt class="filename">smb.conf</tt> file sections define a share control or effect access controls. -Before using any of the following options, please refer to the man page for <tt class="filename">smb.conf</tt>. -</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2912329"></a>User and Group-Based Controls</h3></div></div><div></div></div><p> - User and group-based controls can prove quite useful. In some situations it is distinctly desirable to affect all - file system operations as if a single user were doing so. The use of the <a class="indexterm" name="id2912343"></a><i class="parameter"><tt>force user</tt></i> and - <a class="indexterm" name="id2912356"></a><i class="parameter"><tt>force group</tt></i> behavior will achieve this. In other situations it may be necessary to effect a - paranoia level of control to ensure that only particular authorized persons will be able to access a share or - its contents. Here the use of the <a class="indexterm" name="id2912374"></a><i class="parameter"><tt>valid users</tt></i> or the - <a class="indexterm" name="id2912388"></a><i class="parameter"><tt>invalid users</tt></i> may be most useful. - </p><p> - As always, it is highly advisable to use the least difficult to maintain and the least ambiguous method for - controlling access. Remember, when you leave the scene someone else will need to provide assistance and - if he finds too great a mess or does not understand what you have done, there is risk of - Samba being removed and an alternative solution being adopted. - </p><p> - <link linkend="ugbc"> enumerates these controls. - </p><div class="table"><a name="ugbc"></a><p class="title"><b>Table 13.2. User and Group Based Controls</b></p><table summary="User and Group Based Controls" border="1"><colgroup><col align="left"><col align="justify"></colgroup><thead><tr><th align="center">Control Parameter</th><th align="center">Description - Action - Notes</th></tr></thead><tbody><tr><td align="left"><a class="indexterm" name="id2912501"></a><i class="parameter"><tt>admin users</tt></i></td><td align="justify"><p> - List of users who will be granted administrative privileges on the share. - They will do all file operations as the super-user (root). - Any user in this list will be able to do anything they like on the share, - irrespective of file permissions. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912530"></a><i class="parameter"><tt>force group</tt></i></td><td align="justify"><p> - Specifies a UNIX group name that will be assigned as the default primary group - for all users connecting to this service. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912558"></a><i class="parameter"><tt>force user</tt></i></td><td align="justify"><p> - Specifies a UNIX user name that will be assigned as the default user for all users connecting to this service. - This is useful for sharing files. Incorrect use can cause security problems. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912586"></a><i class="parameter"><tt>guest ok</tt></i></td><td align="justify"><p> - If this parameter is set for a service, then no password is required to connect to the service. Privileges will be - those of the guest account. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912614"></a><i class="parameter"><tt>invalid users</tt></i></td><td align="justify"><p> - List of users that should not be allowed to login to this service. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912640"></a><i class="parameter"><tt>only user</tt></i></td><td align="justify"><p> - Controls whether connections with usernames not in the user list will be allowed. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912666"></a><i class="parameter"><tt>read list</tt></i></td><td align="justify"><p> - List of users that are given read-only access to a service. Users in this list - will not be given write access, no matter what the read only option is set to. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912694"></a><i class="parameter"><tt>username</tt></i></td><td align="justify"><p> - Refer to the <tt class="filename">smb.conf</tt> man page for more information -- this is a complex and potentially misused parameter. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912727"></a><i class="parameter"><tt>valid users</tt></i></td><td align="justify"><p> - List of users that should be allowed to login to this service. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912754"></a><i class="parameter"><tt>write list</tt></i></td><td align="justify"><p> - List of users that are given read-write access to a service. - </p></td></tr></tbody></table></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2912779"></a>File and Directory Permissions-Based Controls</h3></div></div><div></div></div><p> - The following file and directory permission-based controls, if misused, can result in considerable difficulty to - diagnose causes of misconfiguration. Use them sparingly and carefully. By gradually introducing each one by one, - undesirable side effects may be detected. In the event of a problem, always comment all of them out and then gradually - reintroduce them in a controlled way. - </p><p> - Refer to <link linkend="fdpbc"> for information regarding the parameters that may be used to affect file and - directory permission-based access controls. - </p><div class="table"><a name="fdpbc"></a><p class="title"><b>Table 13.3. File and Directory Permission Based Controls</b></p><table summary="File and Directory Permission Based Controls" border="1"><colgroup><col align="left"><col align="justify"></colgroup><thead><tr><th align="center">Control Parameter</th><th align="center">Description - Action - Notes</th></tr></thead><tbody><tr><td align="left"><a class="indexterm" name="id2912884"></a><i class="parameter"><tt>create mask</tt></i></td><td align="justify"><p> - Refer to the <tt class="filename">smb.conf</tt> man page. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912916"></a><i class="parameter"><tt>directory mask</tt></i></td><td align="justify"><p> - The octal modes used when converting DOS modes to UNIX modes when creating UNIX directories. - See also: directory security mask. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912942"></a><i class="parameter"><tt>dos filemode</tt></i></td><td align="justify"><p> - Enabling this parameter allows a user who has write access to the file to modify the permissions on it. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912969"></a><i class="parameter"><tt>force create mode</tt></i></td><td align="justify"><p> - This parameter specifies a set of UNIX mode bit permissions that will always be set on a file created by Samba. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2912996"></a><i class="parameter"><tt>force directory mode</tt></i></td><td align="justify"><p> - This parameter specifies a set of UNIX mode bit permissions that will always be set on a directory created by Samba. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2913024"></a><i class="parameter"><tt>force directory security mode</tt></i></td><td align="justify"><p> - Controls UNIX permission bits modified when a Windows NT client is manipulating UNIX permissions on a directory. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2913052"></a><i class="parameter"><tt>force security mode</tt></i></td><td align="justify"><p> - Controls UNIX permission bits modified when a Windows NT client manipulates UNIX permissions. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2913079"></a><i class="parameter"><tt>hide unreadable</tt></i></td><td align="justify"><p> - Prevents clients from seeing the existence of files that cannot be read. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2913105"></a><i class="parameter"><tt>hide unwriteable files</tt></i></td><td align="justify"><p> - Prevents clients from seeing the existence of files that cannot be written to. Unwriteable directories are shown as usual. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2913133"></a><i class="parameter"><tt>nt acl support</tt></i></td><td align="justify"><p> - This parameter controls whether smbd will attempt to map UNIX permissions into Windows NT access control lists. - </p></td></tr><tr><td align="left"><a class="indexterm" name="id2913160"></a><i class="parameter"><tt>security mask</tt></i></td><td align="justify"><p> - Controls UNIX permission bits modified when a Windows NT client is manipulating the UNIX permissions on a file. - </p></td></tr></tbody></table></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2913187"></a>Miscellaneous Controls</h3></div></div><div></div></div><p> - The following are documented because of the prevalence of administrators creating inadvertent barriers to file - access by not understanding the full implications of <tt class="filename">smb.conf</tt> file settings. See <link linkend="mcoc">. - </p><div class="table"><a name="mcoc"></a><p class="title"><b>Table 13.4. Other Controls</b></p><table summary="Other Controls" border="1"><colgroup><col align="justify"><col align="justify"></colgroup><thead><tr><th align="center">Control Parameter</th><th align="center">Description - Action - Notes</th></tr></thead><tbody><tr><td align="justify"><a class="indexterm" name="id2913282"></a><i class="parameter"><tt>case sensitive</tt></i>, <a class="indexterm" name="id2913296"></a><i class="parameter"><tt>default case</tt></i>, <a class="indexterm" name="id2913310"></a><i class="parameter"><tt>short preserve case</tt></i></td><td align="justify"><p> - This means that all file name lookup will be done in a case sensitive manner. - Files will be created with the precise file name Samba received from the MS Windows client. - </p></td></tr><tr><td align="justify"><a class="indexterm" name="id2913339"></a><i class="parameter"><tt>csc policy</tt></i></td><td align="justify"><p> - Client Side Caching Policy - parallels MS Windows client side file caching capabilities. - </p></td></tr><tr><td align="justify"><a class="indexterm" name="id2913365"></a><i class="parameter"><tt>dont descend</tt></i></td><td align="justify"><p> - Allows specifying a comma-delimited list of directories that the server should always show as empty. - </p></td></tr><tr><td align="justify"><a class="indexterm" name="id2913392"></a><i class="parameter"><tt>dos filetime resolution</tt></i></td><td align="justify"><p> - This option is mainly used as a compatibility option for Visual C++ when used against Samba shares. - </p></td></tr><tr><td align="justify"><a class="indexterm" name="id2913419"></a><i class="parameter"><tt>dos filetimes</tt></i></td><td align="justify"><p> - DOS and Windows allow users to change file time stamps if they can write to the file. POSIX semantics prevent this. - This option allows DOS and Windows behavior. - </p></td></tr><tr><td align="justify"><a class="indexterm" name="id2913448"></a><i class="parameter"><tt>fake oplocks</tt></i></td><td align="justify"><p> - Oplocks are the way that SMB clients get permission from a server to locally cache file operations. If a server grants an - oplock, the client is free to assume that it is the only one accessing the file and it will aggressively cache file data. - </p></td></tr><tr><td align="justify"><a class="indexterm" name="id2913477"></a><i class="parameter"><tt>hide dot files</tt></i>, <a class="indexterm" name="id2913492"></a><i class="parameter"><tt>hide files</tt></i>, <a class="indexterm" name="id2913505"></a><i class="parameter"><tt>veto files</tt></i></td><td align="justify"><p> - Note: MS Windows Explorer allows over-ride of files marked as hidden so they will still be visible. - </p></td></tr><tr><td align="justify"><a class="indexterm" name="id2913532"></a><i class="parameter"><tt>read only</tt></i></td><td align="justify"><p> - If this parameter is yes, then users of a service may not create or modify files in the service's directory. - </p></td></tr><tr><td align="justify"><a class="indexterm" name="id2913559"></a><i class="parameter"><tt>veto files</tt></i></td><td align="justify"><p> - List of files and directories that are neither visible nor accessible. - </p></td></tr></tbody></table></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2913585"></a>Access Controls on Shares</h2></div></div><div></div></div><p> -<a class="indexterm" name="id2913597"></a> - This section deals with how to configure Samba per share access control restrictions. - By default, Samba sets no restrictions on the share itself. Restrictions on the share itself - can be set on MS Windows NT4/200x/XP shares. This can be an effective way to limit who can - connect to a share. In the absence of specific restrictions the default setting is to allow - the global user <tt class="constant">Everyone - Full Control</tt> (full control, change and read). - </p><p> - At this time Samba does not provide a tool for configuring access control setting on the share - itself. Samba does have the capacity to store and act on access control settings, but the only - way to create those settings is to use either the NT4 Server Manager or the Windows 200x MMC for - Computer Management. - </p><p> - Samba stores the per share access control settings in a file called <tt class="filename">share_info.tdb</tt>. - The location of this file on your system will depend on how Samba was compiled. The default location - for Samba's tdb files is under <tt class="filename">/usr/local/samba/var</tt>. If the <tt class="filename">tdbdump</tt> - utility has been compiled and installed on your system, then you can examine the contents of this file - by executing: <b class="command">tdbdump share_info.tdb</b> in the directory containing the tdb files. - </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2913670"></a>Share Permissions Management</h3></div></div><div></div></div><p> - The best tool for the task is platform dependant. Choose the best tool for your environment. - </p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2913682"></a>Windows NT4 Workstation/Server</h4></div></div><div></div></div><p> - The tool you need to use to manage share permissions on a Samba server is the NT Server Manager. - Server Manager is shipped with Windows NT4 Server products but not with Windows NT4 Workstation. - You can obtain the NT Server Manager for MS Windows NT4 Workstation from Microsoft see details below. - </p><div class="procedure"><p class="title"><b>Procedure 13.1. Instructions</b></p><ol type="1"><li><p> - Launch the <span class="application">NT4 Server Manager</span>, click on the Samba server you want to administer. From the menu - select <span class="guimenu">Computer</span>, then click on <span class="guimenuitem">Shared Directories</span>. - </p></li><li><p> - Click on the share that you wish to manage, then click the <span class="guilabel">Properties</span> tab. then click - the <span class="guilabel">Permissions</span> tab. Now you can add or change access control settings as you wish. - </p></li></ol></div></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2913771"></a>Windows 200x/XP</h4></div></div><div></div></div><p> - On <span class="application">MS Windows NT4/200x/XP</span> system access control lists on the share itself are set using native - tools, usually from File Manager. For example, in Windows 200x, right click on the shared folder, - then select <span class="guimenuitem">Sharing</span>, then click on <span class="guilabel">Permissions</span>. The default - Windows NT4/200x permission allows “<span class="quote">Everyone</span>” full control on the share. - </p><p> - MS Windows 200x and later versions come with a tool called the <span class="application">Computer Management</span> snap-in for the - Microsoft Management Console (MMC). This tool is located by clicking on <span class="guimenu">Control Panel -> - Administrative Tools -> Computer Management</span>. - </p><div class="procedure"><p class="title"><b>Procedure 13.2. Instructions</b></p><ol type="1"><li><p> - After launching the MMC with the Computer Management snap-in, click the menu item <span class="guimenuitem">Action</span>, - and select <span class="guilabel">Connect to another computer</span>. If you are not logged onto a domain you will be prompted - to enter a domain login user identifier and a password. This will authenticate you to the domain. - If you are already logged in with administrative privilege, this step is not offered. - </p></li><li><p> - If the Samba server is not shown in the <span class="guilabel">Select Computer</span> box, type in the name of the target - Samba server in the field <span class="guilabel">Name:</span>. Now click the on <span class="guibutton">[+]</span> next to - <span class="guilabel">System Tools</span>, then on the <span class="guibutton">[+]</span> next to <span class="guilabel">Shared Folders</span> in the - left panel. - </p></li><li><p> - In the right panel, double-click on the share on which you wish to set access control permissions. - Then click the tab <span class="guilabel">Share Permissions</span>. It is now possible to add access control entities - to the shared folder. Remember to set what type of access (full control, change, read) you - wish to assign for each entry. - </p></li></ol></div><div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Warning</h3><p> - Be careful. If you take away all permissions from the <tt class="constant">Everyone</tt> user without removing this user, - effectively no user will be able to access the share. This is a result of what is known as - ACL precedence. Everyone with <span class="emphasis"><em>no access</em></span> means that <tt class="constant">MaryK</tt> who is part of the group - <tt class="constant">Everyone</tt> will have no access even if she is given explicit full control access. - </p></div></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2913978"></a>MS Windows Access Control Lists and UNIX Interoperability</h2></div></div><div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2913986"></a>Managing UNIX Permissions Using NT Security Dialogs</h3></div></div><div></div></div><p> -<a class="indexterm" name="id2913998"></a> - Windows NT clients can use their native security settings dialog box to view and modify the - underlying UNIX permissions. - </p><p> - This ability is careful not to compromise the security of the UNIX host on which Samba is running, and - still obeys all the file permission rules that a Samba administrator can set. - </p><p> - Samba does not attempt to go beyond POSIX ACLs, so the various finer-grained access control - options provided in Windows are actually ignored. - </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> - All access to UNIX/Linux system files via Samba is controlled by the operating system file access controls. - When trying to figure out file access problems, it is vitally important to find the identity of the Windows - user as it is presented by Samba at the point of file access. This can best be determined from the - Samba log files. - </p></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2914042"></a>Viewing File Security on a Samba Share</h3></div></div><div></div></div><p> - From an NT4/2000/XP client, right click on any file or directory in a Samba-mounted drive letter - or UNC path. When the menu pops up, click on the <span class="guilabel">Properties</span> entry at the bottom - of the menu. This brings up the file <tt class="constant">Properties</tt> dialog box. Click on the - <span class="guilabel">Security</span> tab and you will see three buttons: <span class="guibutton">Permissions</span>, - <span class="guibutton">Auditing</span>, and <span class="guibutton">Ownership</span>. The <span class="guibutton">Auditing</span> - button will cause either an error message <span class="errorname">`A requested privilege is not held by the client'</span> - to appear if the user is not the NT Administrator, or a dialog which is intended to allow an Administrator - to add auditing requirements to a file if the user is logged on as the NT Administrator. This dialog is - non-functional with a Samba share at this time, as the only useful button, the <span class="guibutton">Add</span> - button, will not currently allow a list of users to be seen. - </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2914124"></a>Viewing File Ownership</h3></div></div><div></div></div><p> - Clicking on the <span class="guibutton">Ownership</span> button brings up a dialog box telling you who owns - the given file. The owner name will be displayed like this: - </p><p> - <b class="command">“<span class="quote">SERVER\user (Long name)</span>”</b> - </p><p> - <i class="replaceable"><tt>SERVER</tt></i> is the NetBIOS name of the Samba server, <i class="replaceable"><tt>user</tt></i> - is the user name of the UNIX user who owns the file, and <i class="replaceable"><tt>(Long name)</tt></i> is the - descriptive string identifying the user (normally found in the GECOS field of the UNIX password database). - Click on the <span class="guibutton">Close </span> button to remove this dialog. - </p><p> - If the parameter <a class="indexterm" name="id2914189"></a><i class="parameter"><tt>nt acl support</tt></i> is set to <tt class="constant">false</tt>, - the file owner will be shown as the NT user <span class="emphasis"><em>Everyone</em></span>. - </p><p> - The <span class="guibutton">Take Ownership</span> button will not allow you to change the ownership of this file to - yourself (clicking it will display a dialog box complaining that the user you are currently logged onto - the NT client cannot be found). The reason for this is that changing the ownership of a file is a privileged - operation in UNIX, available only to the <span class="emphasis"><em>root</em></span> user. As clicking on this button causes - NT to attempt to change the ownership of a file to the current user logged into the NT clienti, this will - not work with Samba at this time.</p><p> - There is an NT <b class="command">chown</b> command that will work with Samba and allow a user with Administrator privilege connected - to a Samba server as root to change the ownership of files on both a local NTFS filesystem or remote mounted NTFS - or Samba drive. This is available as part of the <span class="application">Seclib</span> NT security library written - by Jeremy Allison of the Samba Team, and is available from the main Samba FTP site.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2914264"></a>Viewing File or Directory Permissions</h3></div></div><div></div></div><p> - The third button is the <span class="guibutton">Permissions</span> button. Clicking on this brings up a dialog box - that shows both the permissions and the UNIX owner of the file or directory. The owner is displayed like this: - </p><p><b class="command"><i class="replaceable"><tt>SERVER</tt></i>\ - <i class="replaceable"><tt>user</tt></i> - <i class="replaceable"><tt>(Long name)</tt></i></b></p><p>Where <i class="replaceable"><tt>SERVER</tt></i> is the NetBIOS name of the Samba server, - <i class="replaceable"><tt>user</tt></i> is the user name of the UNIX user who owns the file, and - <i class="replaceable"><tt>(Long name)</tt></i> is the descriptive string identifying the user (normally found in the - GECOS field of the UNIX password database).</p><p> - If the parameter <a class="indexterm" name="id2914328"></a><i class="parameter"><tt>nt acl support</tt></i> is set to <tt class="constant">false</tt>, - the file owner will be shown as the NT user <tt class="constant">Everyone</tt> and the permissions will be - shown as NT “<span class="quote">Full Control</span>”. - </p><p> - The permissions field is displayed differently for files and directories, so I'll describe the way file permissions - are displayed first. - </p><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2914362"></a>File Permissions</h4></div></div><div></div></div><p>The standard UNIX user/group/world triplet and the corresponding <tt class="constant">read, write, execute</tt> permissions - triplets are mapped by Samba into a three element NT ACL with the “<span class="quote">r</span>”, “<span class="quote">w</span>” and “<span class="quote">x</span>” bits mapped into the corresponding - NT permissions. The UNIX world permissions are mapped into the global NT group <tt class="constant">Everyone</tt>, followed - by the list of permissions allowed for UNIX world. The UNIX owner and group permissions are displayed as an NT - <span class="guiicon">user</span> icon and an NT <span class="guiicon">local group</span> icon, respectively, followed by the list - of permissions allowed for the UNIX user and group.</p><p>Because many UNIX permission sets do not map into common NT names such as <tt class="constant">read</tt>, - <tt class="constant">change</tt> or <tt class="constant">full control</tt>, usually the permissions will be prefixed - by the words <tt class="constant">Special Access</tt> in the NT display list.</p><p>But what happens if the file has no permissions allowed for a particular UNIX user group or world component? In order - to allow “<span class="quote">no permissions</span>” to be seen and modified Samba then overloads the NT <tt class="constant">Take Ownership</tt> ACL attribute - (which has no meaning in UNIX) and reports a component with no permissions as having the NT <b class="command">O</b> bit set. - This was chosen, of course, to make it look like a zero, meaning zero permissions. More details on the decision behind this is - given below.</p></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2914471"></a>Directory Permissions</h4></div></div><div></div></div><p>Directories on an NT NTFS file system have two different sets of permissions. The first set is the ACL set on the - directory itself, which is usually displayed in the first set of parentheses in the normal <tt class="constant">RW</tt> - NT style. This first set of permissions is created by Samba in exactly the same way as normal file permissions are, described - above, and is displayed in the same way.</p><p>The second set of directory permissions has no real meaning in the UNIX permissions world and represents the <tt class="constant"> - inherited</tt> permissions that any file created within this directory would inherit.</p><p>Samba synthesises these inherited permissions for NT by returning as an NT ACL the UNIX permission mode that a new file - created by Samba on this share would receive.</p></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2914515"></a>Modifying File or Directory Permissions</h3></div></div><div></div></div><p>Modifying file and directory permissions is as simple - as changing the displayed permissions in the dialog box, and - clicking on <span class="guibutton">OK</span>. However, there are - limitations that a user needs to be aware of, and also interactions - with the standard Samba permission masks and mapping of DOS - attributes that need to also be taken into account.</p><p>If the parameter <a class="indexterm" name="id2914543"></a><i class="parameter"><tt>nt acl support</tt></i> - is set to <tt class="constant">false</tt>, any attempt to set - security permissions will fail with an <span class="errorname">`Access Denied' - </span> message.</p><p>The first thing to note is that the <span class="guibutton">Add</span> - button will not return a list of users in Samba (it will give - an error message saying <span class="errorname">`The remote procedure call failed - and did not execute'</span>). This means that you can only - manipulate the current user/group/world permissions listed in - the dialog box. This actually works quite well as these are the - only permissions that UNIX actually has.</p><p>If a permission triplet (either user, group, or world) - is removed from the list of permissions in the NT dialog box, - then when the <span class="guibutton">OK</span> button is pressed it will - be applied as “<span class="quote">no permissions</span>” on the UNIX side. If you then - view the permissions again, the “<span class="quote">no permissions</span>” entry will appear - as the NT <b class="command">O</b> flag, as described above. This - allows you to add permissions back to a file or directory once - you have removed them from a triplet component.</p><p>As UNIX supports only the “<span class="quote">r</span>”, “<span class="quote">w</span>” and “<span class="quote">x</span>” bits of - an NT ACL, if other NT security attributes such as <tt class="constant">Delete Access</tt> are - selected they will be ignored when applied on the Samba server.</p><p>When setting permissions on a directory, the second - set of permissions (in the second set of parentheses) is - by default applied to all files within that directory. If this - is not what you want, you must uncheck the <span class="guilabel">Replace - permissions on existing files</span> checkbox in the NT - dialog before clicking on <span class="guibutton">OK</span>.</p><p>If you wish to remove all permissions from a - user/group/world component, you may either highlight the - component and click on the <span class="guibutton">Remove</span> button, - or set the component to only have the special <tt class="constant">Take - Ownership</tt> permission (displayed as <b class="command">O - </b>) highlighted.</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2914698"></a>Interaction with the Standard Samba “<span class="quote">create mask</span>” Parameters</h3></div></div><div></div></div><p>There are four parameters that control interaction with the standard Samba <i class="parameter"><tt>create mask</tt></i> parameters. - These are: - - </p><div class="itemizedlist"><ul type="disc"><li><a class="indexterm" name="id2914726"></a><i class="parameter"><tt>security mask</tt></i></li><li><a class="indexterm" name="id2914742"></a><i class="parameter"><tt>force security mode</tt></i></li><li><a class="indexterm" name="id2914757"></a><i class="parameter"><tt>directory security mask</tt></i></li><li><a class="indexterm" name="id2914773"></a><i class="parameter"><tt>force directory security mode</tt></i></li></ul></div><p> - - </p><p>Once a user clicks on <span class="guibutton">OK</span> to apply the - permissions, Samba maps the given permissions into a user/group/world - r/w/x triplet set, and then checks the changed permissions for a - file against the bits set in the - <a class="indexterm" name="id2914803"></a><i class="parameter"><tt>security mask</tt></i> parameter. Any bits that - were changed that are not set to “<span class="quote">1</span>” in this parameter are left alone - in the file permissions.</p><p>Essentially, zero bits in the <a class="indexterm" name="id2914828"></a><i class="parameter"><tt>security mask</tt></i> - may be treated as a set of bits the user is <span class="emphasis"><em>not</em></span> - allowed to change, and one bits are those the user is allowed to change. - </p><p>If not explicitly set, this parameter defaults to the same value as - the <a class="indexterm" name="id2914853"></a><i class="parameter"><tt>create mask</tt></i> parameter. To allow a user to modify all the - user/group/world permissions on a file, set this parameter to 0777. - </p><p>Next Samba checks the changed permissions for a file against the bits set in the - <a class="indexterm" name="id2914875"></a><i class="parameter"><tt>force security mode</tt></i> parameter. Any bits - that were changed that correspond to bits set to “<span class="quote">1</span>” in this parameter - are forced to be set.</p><p>Essentially, bits set in the <i class="parameter"><tt>force security mode</tt></i> parameter - may be treated as a set of bits that, when modifying security on a file, the user has always set to be “<span class="quote">on</span>”.</p><p>If not explicitly set, this parameter defaults to the same value - as the <a class="indexterm" name="id2914918"></a><i class="parameter"><tt>force create mode</tt></i> parameter. - To allow a user to modify all the user/group/world permissions on a file - with no restrictions set this parameter to 000. The - <a class="indexterm" name="id2914935"></a><i class="parameter"><tt>security mask</tt></i> and <i class="parameter"><tt>force - security mode</tt></i> parameters are applied to the change - request in that order.</p><p>For a directory, Samba will perform the same operations as - described above for a file except it uses the parameter <i class="parameter"><tt> - directory security mask</tt></i> instead of <i class="parameter"><tt>security - mask</tt></i>, and <i class="parameter"><tt>force directory security mode - </tt></i> parameter instead of <i class="parameter"><tt>force security mode - </tt></i>.</p><p>The <a class="indexterm" name="id2914996"></a><i class="parameter"><tt>directory security mask</tt></i> parameter - by default is set to the same value as the <i class="parameter"><tt>directory mask - </tt></i> parameter and the <i class="parameter"><tt>force directory security - mode</tt></i> parameter by default is set to the same value as - the <a class="indexterm" name="id2915027"></a><i class="parameter"><tt>force directory mode</tt></i> parameter. - In this way Samba enforces the permission restrictions that - an administrator can set on a Samba share, while still allowing users - to modify the permission bits within that restriction.</p><p>If you want to set up a share that allows users full control - in modifying the permission bits on their files and directories and - does not force any particular bits to be set “<span class="quote">on</span>”, then set the following - parameters in the <tt class="filename">smb.conf</tt> file in that share-specific section: - </p><table class="simplelist" border="0" summary="Simple list"><tr><td><i class="parameter"><tt>security mask = 0777</tt></i></td></tr><tr><td><i class="parameter"><tt>force security mode = 0</tt></i></td></tr><tr><td><i class="parameter"><tt>directory security mask = 0777</tt></i></td></tr><tr><td><i class="parameter"><tt>force directory security mode = 0</tt></i></td></tr></table></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2915106"></a>Interaction with the Standard Samba File Attribute Mapping</h3></div></div><div></div></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>Samba maps some of the DOS attribute bits (such as “<span class="quote">read - only</span>”) into the UNIX permissions of a file. This means there can - be a conflict between the permission bits set via the security - dialog and the permission bits set by the file attribute mapping. - </p></div><p>If a file has no UNIX read access for the owner, it will show up - as “<span class="quote">read only</span>” in the standard file attributes tabbed dialog. - Unfortunately, this dialog is the same one that contains the security information - in another tab.</p><p>What this can mean is that if the owner changes the permissions - to allow himself read access using the security dialog, clicks on - <span class="guibutton">OK</span> to get back to the standard attributes tab - dialog, and clicks on <span class="guibutton">OK</span> on that dialog, then - NT will set the file permissions back to read-only (as that is what - the attributes still say in the dialog). This means that after setting - permissions and clicking on <span class="guibutton">OK</span> to get back to the - attributes dialog, you should always press <span class="guibutton">Cancel</span> - rather than <span class="guibutton">OK</span> to ensure that your changes - are not overridden.</p></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2915195"></a>Common Errors</h2></div></div><div></div></div><p> -File, directory and share access problems are common on the mailing list. The following -are examples taken from the mailing list in recent times. -</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2915209"></a>Users Cannot Write to a Public Share</h3></div></div><div></div></div><p> - “<span class="quote"> - We are facing some troubles with file/directory permissions. I can log on the domain as admin user(root), - and there's a public share on which everyone needs to have permission to create/modify files, but only - root can change the file, no one else can. We need to constantly go to the server to - <b class="userinput"><tt>chgrp -R users *</tt></b> and <b class="userinput"><tt>chown -R nobody *</tt></b> to allow others users to change the file. - </span>” - </p><p> - There are many ways to solve this problem and here are a few hints: - </p><div class="procedure"><ol type="1"><li><p> - Go to the top of the directory that is shared. - </p></li><li><p> - Set the ownership to what ever public owner and group you want -</p><pre class="screen"> -<tt class="prompt">$ </tt>find 'directory_name' -type d -exec chown user.group {}\; -<tt class="prompt">$ </tt>find 'directory_name' -type d -exec chmod 6775 'directory_name' -<tt class="prompt">$ </tt>find 'directory_name' -type f -exec chmod 0775 {} \; -<tt class="prompt">$ </tt>find 'directory_name' -type f -exec chown user.group {}\; -</pre><p> - </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> - The above will set the <tt class="constant">sticky bit</tt> on all directories. Read your - UNIX/Linux man page on what that does. It causes the OS to assign - to all files created in the directories the ownership of the - directory. - </p></div></li><li><p> - - Directory is: <i class="replaceable"><tt>/foodbar</tt></i> -</p><pre class="screen"> -<tt class="prompt">$ </tt><b class="userinput"><tt>chown jack.engr /foodbar</tt></b> -</pre><p> - </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> - </p><p>This is the same as doing:</p><p> -</p><pre class="screen"> -<tt class="prompt">$ </tt><b class="userinput"><tt>chown jack /foodbar</tt></b> -<tt class="prompt">$ </tt><b class="userinput"><tt>chgrp engr /foodbar</tt></b> -</pre><p> - </p></div></li><li><p>Now type: - -</p><pre class="screen"> -<tt class="prompt">$ </tt><b class="userinput"><tt>chmod 6775 /foodbar</tt></b> -<tt class="prompt">$ </tt><b class="userinput"><tt>ls -al /foodbar/..</tt></b> -</pre><p> - - </p><p>You should see: -</p><pre class="screen"> -drwsrwsr-x 2 jack engr 48 2003-02-04 09:55 foodbar -</pre><p> - </p></li><li><p>Now type: -</p><pre class="screen"> -<tt class="prompt">$ </tt><b class="userinput"><tt>su - jill</tt></b> -<tt class="prompt">$ </tt><b class="userinput"><tt>cd /foodbar</tt></b> -<tt class="prompt">$ </tt><b class="userinput"><tt>touch Afile</tt></b> -<tt class="prompt">$ </tt><b class="userinput"><tt>ls -al</tt></b> -</pre><p> - </p><p> - You should see that the file <tt class="filename">Afile</tt> created by Jill will have ownership - and permissions of Jack, as follows: -</p><pre class="screen"> --rw-r--r-- 1 jack engr 0 2003-02-04 09:57 Afile -</pre><p> - </p></li><li><p> - Now in your <tt class="filename">smb.conf</tt> for the share add: - </p><table class="simplelist" border="0" summary="Simple list"><tr><td><i class="parameter"><tt>force create mode = 0775</tt></i></td></tr><tr><td><i class="parameter"><tt>force direcrtory mode = 6775</tt></i></td></tr></table><p> - </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> - These procedures are needed only if your users are not members of the group - you have used. That is if within the OS do not have write permission on the directory. - </p></div><p> - An alternative is to set in the <tt class="filename">smb.conf</tt> entry for the share: - </p><table class="simplelist" border="0" summary="Simple list"><tr><td><i class="parameter"><tt>force user = jack</tt></i></td></tr><tr><td><i class="parameter"><tt>force group = engr</tt></i></td></tr></table><p> - </p></li></ol></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2915635"></a>File Operations Done as <span class="emphasis"><em>root</em></span> with <span class="emphasis"><em>force user</em></span> Set</h3></div></div><div></div></div><p> - When you have a user in <a class="indexterm" name="id2915654"></a><i class="parameter"><tt>admin users</tt></i>, Samba will always do file operations for - this user as <span class="emphasis"><em>root</em></span>, even if <a class="indexterm" name="id2915674"></a><i class="parameter"><tt>force user</tt></i> has been set. - </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2915690"></a>MS Word with Samba Changes Owner of File</h3></div></div><div></div></div><p> - <span class="emphasis"><em>Question:</em></span> “<span class="quote">When user B saves a word document that is owned by user A the updated file is now owned by user B. - Why is Samba doing this? How do I fix this?</span>” - </p><p> - <span class="emphasis"><em>Answer:</em></span> Word does the following when you modify/change a Word document: MS Word creates a NEW document with - a temporary name, Word then closes the old document and deletes it, Word then renames the new document to the original document name. - There is no mechanism by which Samba can in any way know that the new document really should be owned by the owners - of the original file. Samba has no way of knowing that the file will be renamed by MS Word. As far as Samba is able - to tell, the file that gets created is a NEW file, not one that the application (Word) is updating. - </p><p> - There is a work-around to solve the permissions problem. That work-around involves understanding how you can manage file - system behavior from within the <tt class="filename">smb.conf</tt> file, as well as understanding how UNIX file systems work. Set on the directory - in which you are changing Word documents: <b class="command">chmod g+s `directory_name'</b> This ensures that all files will - be created with the group that owns the directory. In <tt class="filename">smb.conf</tt> share declaration section set: - </p><p> - </p><table class="simplelist" border="0" summary="Simple list"><tr><td><i class="parameter"><tt>force create mode = 0660</tt></i></td></tr><tr><td><i class="parameter"><tt>force directory mode = 0770</tt></i></td></tr></table><p> - </p><p> - These two settings will ensure that all directories and files that get created in the share will be read/writable by the - owner and group set on the directory itself. - </p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="groupmapping.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="optional.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="locking.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 12. 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