1 <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 4//EN">
3 <TITLE>User Guide</TITLE>
4 <!-- Begin Header Records ========================================== -->
5 <!-- /tmp/idwt3629/auusg000.scr converted by idb2h R4.2 (359) ID -->
6 <!-- Workbench Version (AIX) on 2 Oct 2000 at 14:38:44 -->
7 <META HTTP-EQUIV="updated" CONTENT="Mon, 02 Oct 2000 14:38:42">
8 <META HTTP-EQUIV="review" CONTENT="Tue, 02 Oct 2001 14:38:42">
9 <META HTTP-EQUIV="expires" CONTENT="Wed, 02 Oct 2002 14:38:42">
11 <!-- (C) IBM Corporation 2000. All Rights Reserved -->
12 <BODY bgcolor="ffffff">
13 <!-- End Header Records ============================================ -->
14 <A NAME="Top_Of_Page"></A>
16 <HR><P ALIGN="center"> <A HREF="../index.htm"><IMG SRC="../books.gif" BORDER="0" ALT="[Return to Library]"></A> <A HREF="auusg002.htm#ToC"><IMG SRC="../toc.gif" BORDER="0" ALT="[Contents]"></A> <A HREF="auusg003.htm"><IMG SRC="../prev.gif" BORDER="0" ALT="[Previous Topic]"></A> <A HREF="#Bot_Of_Page"><IMG SRC="../bot.gif" BORDER="0" ALT="[Bottom of Topic]"></A> <A HREF="auusg005.htm"><IMG SRC="../next.gif" BORDER="0" ALT="[Next Topic]"></A> <A HREF="auusg013.htm#HDRINDEX"><IMG SRC="../index.gif" BORDER="0" ALT="[Index]"></A> <P>
17 <HR><H1><A NAME="HDRWQ2" HREF="auusg002.htm#ToC_7">An Introduction to AFS</A></H1>
18 <P>This chapter introduces basic AFS concepts and terms.
19 It assumes that you are already familiar with standard UNIX commands, file
20 protection, and pathname conventions.
21 <HR><H2><A NAME="HDRWQ3" HREF="auusg002.htm#ToC_8">AFS Concepts</A></H2>
22 <P>AFS makes it easy for people to work together on the same
23 files, no matter where the files are located. AFS users do not have to
24 know which machine is storing a file, and administrators can move files from
25 machine to machine without interrupting user access. Users always
26 identify a file by the same pathname and AFS finds the correct file
27 automatically, just as happens in the local file system on a single
28 machine. While AFS makes file sharing easy, it does not compromise the
29 security of the shared files. It provides a sophisticated protection
33 <P><H3><A NAME="Header_9" HREF="auusg002.htm#ToC_9">Client/Server Computing</A></H3>
34 <P>AFS uses a <I>client/server computing</I> model. In
35 client/server computing, there are two types of machines. <I>Server
36 machines</I> store data and perform services for client machines.
37 <I>Client machines</I> perform computations for users and access data and
38 services provided by server machines. Some machines act as both clients
39 and servers. In most cases, you work on a client machine, accessing
40 files stored on a file server machine.
47 <P><H3><A NAME="Header_10" HREF="auusg002.htm#ToC_10">Distributed File Systems</A></H3>
48 <P>AFS is a <I>distributed file system</I> which joins together the
49 file systems of multiple file server machines, making it as easy to access
50 files stored on a remote file server machine as files stored on the local
51 disk. A distributed file system has two main advantages over a
52 conventional centralized file system:
55 <P><LI>Increased availability: A copy of a popular file, such as the binary
56 for an application program, can be stored on many file server machines.
57 An outage on a single machine or even multiple machines does not necessarily
58 make the file unavailable. Instead, user requests for the program are
59 routed to accessible machines. With a centralized file system, the loss
60 of the central file storage machine effectively shuts down the entire
62 <P><LI>Increased efficiency: In a distributed file system, the work load is
63 distributed over many smaller file server machines that tend to be more fully
64 utilized than the larger (and usually more expensive) file storage machine of
65 a centralized file system.
67 <P>AFS hides its distributed nature, so working with AFS files looks and feels
68 like working with files stored on your local machine, except that you can
69 access many more files. And because AFS relies on the power of
70 users' client machines for computation, increasing the number of AFS
71 users does not slow AFS performance appreciably, making it a very efficient
72 computing environment.
73 <P><H3><A NAME="HDRWQ4" HREF="auusg002.htm#ToC_11">AFS Filespace and Local Filespace</A></H3>
75 <P>AFS acts as an extension of your machine's local UNIX file
76 system. Your system administrator creates a directory on the local disk
77 of each AFS client machine to act as a gateway to AFS. By convention,
78 this directory is called <B>/afs</B>, and it functions as the root of the
83 <P>Just like the UNIX file system, AFS uses a hierarchical file structure (a
84 tree). Under the <B>/afs</B> root directory are subdirectories
85 created by your system administrator, including your home directory.
86 Other directories that are at the same level of the local file system as
87 <B>/afs</B>, such as <B>/usr</B>, <B>/etc</B>, or <B>/bin</B>,
88 can either be located on your local disk or be links to AFS
89 directories. Files relevant only to the local machine are usually
90 stored on the local machine. All other files can be stored in AFS,
91 enabling many users to share them and freeing the local machine's disk
93 <TABLE><TR><TD ALIGN="LEFT" VALIGN="TOP"><B>Note:</B></TD><TD ALIGN="LEFT" VALIGN="TOP">You can use AFS commands only on files in the AFS filespace or the local
94 directories that are links to the AFS filespace.
96 <P><H3><A NAME="HDRWQ5" HREF="auusg002.htm#ToC_12">Cells and Sites</A></H3>
97 <P>The <I>cell</I> is the administrative domain in
98 AFS. Each cell's administrators determine how client machines are
99 configured and how much storage space is available to each user. The
100 organization corresponding to a cell can be a company, a university
101 department, or any defined group of users. From a hardware perspective,
102 a cell is a grouping of client machines and server machines defined to belong
104 <A NAME="IDX760"></A>
105 An AFS <I>site</I> is a grouping of one or more related cells. For
106 example, the cells at the ABC Corporation form a single site.
107 <A NAME="IDX761"></A>
108 <P>By convention, the subdirectories of the <B>/afs</B> directory are
109 cellular filespaces, each of which contains subdirectories and files that
110 belong to a single cell. For example, directories and files relevant to
111 the ABC Corporation cell are stored in the subdirectory
113 <P>While each cell organizes and maintains its own filespace, it can also
114 connect with the filespace of other AFS cells. The result is a huge
115 filespace that enables file sharing within and across cells.
116 <A NAME="IDX762"></A>
117 <P>The cell to which your client machine belongs is called your <I>local
118 cell</I>. All other cells in the AFS filespace are termed
119 <I>foreign cells</I>.
120 <A NAME="IDX763"></A>
121 <A NAME="IDX764"></A>
122 <A NAME="IDX765"></A>
123 <P><H3><A NAME="HDRWQ6" HREF="auusg002.htm#ToC_13">Volumes and Mount Points</A></H3>
124 <P>The storage disks in a computer are divided into sections
125 called <I>partitions</I>. AFS further divides partitions into units
126 called <I>volumes</I>, each of which houses a subtree of related files and
127 directories. The volume provides a convenient container for storing
128 related files and directories. Your system administrators can move
129 volumes from one file server machine to another without your noticing, because
130 AFS automatically tracks a volume's location.
131 <A NAME="IDX766"></A>
132 <A NAME="IDX767"></A>
133 <P>You access the contents of a volume by accessing its <I>mount point</I>
134 in the AFS filespace. A mount point is a special file system element
135 that looks and acts like a regular UNIX directory, but tells AFS the
136 volume's name. When you change to a different directory (by using
137 the <B>cd</B> command, for example) you sometimes <I>cross</I> a mount
138 point and start accessing the contents of a different volume than
139 before. You normally do not notice the crossing, however, because AFS
140 automatically interprets mount points and retrieves the contents of the new
141 directory from the appropriate volume. You do not need to track which
142 volume, partition, or file server machine is housing a directory's
143 contents. If you are interested, though, you can learn a volume's
144 location; for instructions, see <A HREF="auusg006.htm#HDRWQ40">Locating Files and Directories</A>.
145 <A NAME="IDX768"></A>
146 <A NAME="IDX769"></A>
147 <P>If your system administrator has followed the conventional practice, your
148 home directory corresponds to one volume, which keeps its contents together on
149 one partition of a file server machine. User volumes are typically
150 named <B>user.</B><VAR>username</VAR>. For example, the volume
151 for a user named <B>smith</B> in the cell <B>abc.com</B> is
152 called <B>user.smith</B> and is mounted at the directory
153 <B>/afs/abc.com/usr/smith</B>.
154 <A NAME="IDX770"></A>
155 <P>Because AFS volumes are stored on different file server machines, when a
156 machine becomes unavailable only the volumes on that machine are
157 inaccessible. Volumes stored on other machines are still
158 accessible. However, if a volume's mount point resides in a volume
159 that is stored on an unavailable machine, the former volume is also
160 inaccessible. For that reason, volumes containing frequently used
161 directories (for example, <B>/afs</B> and
162 <B>/afs/</B><VAR>cellname</VAR>) are often copied and distributed to many
163 file server machines.
164 <P><H3><A NAME="HDRWQ7" HREF="auusg002.htm#ToC_14">Volume Quotas</A></H3>
165 <A NAME="IDX771"></A>
166 <P>Each volume has a size limit, or <I>quota</I>, assigned by the system
167 administrator. A volume's quota determines the maximum amount of
168 disk space the volume can consume. If you attempt to exceed a
169 volume's quota, you receive an error message. For instructions on
170 checking volume quota, see <A HREF="auusg006.htm#HDRWQ39">Displaying Volume Quota</A>.
171 <P>Volumes have completely independent quotas. For example, say that
172 the current working directory is <B>/afs/abc.com/usr/smith</B>,
173 which is the mount point for the <B>user.smith</B> volume with 1000
174 free blocks. You try to copy a 500 block file from the current working
175 directory to the <B>/afs/abc.com/usr/pat</B> directory, the mount
176 point for the volume <B>user.pat</B>. However, you get an
177 error message saying there is not enough space. You check the volume
178 quota for <B>user.pat</B>, and find that the volume only has 50
180 <HR><H2><A NAME="HDRWQ8" HREF="auusg002.htm#ToC_15">Using Files in AFS</A></H2>
181 <P><H3><A NAME="HDRWQ9" HREF="auusg002.htm#ToC_16">The Cache Manager</A></H3>
182 <P>You can access the AFS filespace only when working on an AFS
183 client machine. The <I>Cache Manager</I> on that machine is your
184 agent in accessing information stored in the AFS filespace. When you
185 access a file, the Cache Manager on your client machine requests the file from
186 the appropriate file server machine and stores (<I>caches</I>) a copy of
187 it on your client machine's local disk. Application programs on
188 your client machine use the local, cached copy of the file. This
189 improves performance because it is much faster to use a local file than to
190 send requests for file data across the network to the file server
192 <A NAME="IDX772"></A>
193 <A NAME="IDX773"></A>
194 <A NAME="IDX774"></A>
195 <A NAME="IDX775"></A>
196 <P>Because application programs use the cached copy of a file, any changes you
197 make are not necessarily stored permanently to the central version stored on
198 the file server machine until the file closes. At that point, the Cache
199 Manager writes your changes back to the file server machine, where they
200 replace the corresponding parts of the existing file. Some application
201 programs close a file in this way each time you issue their <B>save</B>
202 command (and then immediately reopen the file so that you can continue
203 working). With other programs, issuing the <B>save</B> command
204 writes the changes only to the local cached copy. If you use the latter
205 type of text editor, you need to close the file periodically to make sure your
206 changes are stored permanently.
207 <P>If a file server machine becomes inaccessible, you can continue working
208 with the local, cached copy of a file fetched from that machine, but you
209 cannot save your changes permanently until the server machine is again
211 <P><H3><A NAME="HDRWQ10" HREF="auusg002.htm#ToC_17">Updating Copies of Cached Files</A></H3>
212 <A NAME="IDX776"></A>
213 <A NAME="IDX777"></A>
214 <P>When the central version of a file changes on the file server machine, the
215 AFS <I>File Server</I> process running on that machine advises all other
216 Cache Managers with copies of that file that their version is no longer
217 valid. AFS has a special mechanism for performing these notifications
218 efficiently. When the File Server sends the Cache Manager a copy of a
219 modifiable file, it also sends a <I>callback</I>. A callback
220 functions as a promise from the File Server to contact the Cache Manager if
221 the centrally stored copy of the file is changed while it is being
222 used. If that happens, the File Server <I>breaks</I> the
223 callback. If you run a program that requests data from the changed
224 file, the Cache Manager notices the broken callback and gets an updated copy
225 of the file from the File Server. Callbacks ensure that you are working
226 with the most recent copy of a file.
227 <TABLE><TR><TD ALIGN="LEFT" VALIGN="TOP"><B>Note:</B></TD><TD ALIGN="LEFT" VALIGN="TOP">The callback mechanism does not guarantee that you immediately see the
228 changes someone else makes to a file you are using. Your Cache Manager
229 does not notice the broken callback until your application program asks it for
230 more data from the file.
232 <P><H3><A NAME="Header_18" HREF="auusg002.htm#ToC_18">Multiple Users Modifying Files</A></H3>
233 <A NAME="IDX778"></A>
234 <A NAME="IDX779"></A>
235 <P>Like a standard UNIX file system, AFS preserves only the changes to a file
236 that are saved last, regardless of who made the changes. When
237 collaborating with someone on the same files, you must coordinate your work to
238 avoid overwriting each other's changes. You can use AFS access
239 control lists (ACLs) to limit the ability of other users to access or change
240 your files, and so prevent them from accidentally overwriting your
241 files. See <A HREF="auusg007.htm#HDRWQ44">Protecting Your Directories and Files</A>.
242 <HR><H2><A NAME="HDRWQ11" HREF="auusg002.htm#ToC_19">AFS Security</A></H2>
243 <A NAME="IDX780"></A>
244 <A NAME="IDX781"></A>
245 <P>AFS makes it easy for many users to access the same files, but also uses
246 several mechanisms to ensure that only authorized users access the AFS
247 filespace. The mechanisms include the following:
249 <P><LI>Passwords and mutual authentication ensure that only authorized users
251 <P><LI>Access control lists enable users to restrict or permit access to their
254 <P><H3><A NAME="HDRWQ12" HREF="auusg002.htm#ToC_20">Passwords and Mutual Authentication</A></H3>
255 <A NAME="IDX782"></A>
256 <A NAME="IDX783"></A>
257 <A NAME="IDX784"></A>
258 <P>AFS uses two related mechanisms to ensure that only authorized users access
259 the filespace: passwords and mutual authentication. Both
260 mechanisms require that a user prove his or her identity.
261 <P>When you first identify yourself to AFS, you must provide the password
262 associated with your username, to prove that you are who you say you
263 are. When you provide the correct password, you become
264 <I>authenticated</I> and your Cache Manager receives a
265 <I>token</I>. A token is a package of information that is scrambled
266 by an AFS authentication program using your AFS password as a key. Your
267 Cache Manager can unscramble the token because it knows your password and
268 AFS's method of scrambling.
269 <A NAME="IDX785"></A>
270 <A NAME="IDX786"></A>
271 <P>The token acts as proof to AFS server programs that you are authenticated
272 as a valid AFS user. It serves as the basis for the second means
273 through which AFS creates security, called <I>mutual
274 authentication</I>. Under mutual authentication, both parties
275 communicating across the network prove their identities to one another.
276 AFS requires mutual authentication whenever a server and client (most often, a
277 Cache Manager) communicate with each other.
278 <P>The mutual authentication protocol that AFS uses is designed to make it
279 very difficult for people to authenticate fraudulently. When your Cache
280 Manager contacts a File Server on your behalf, it sends the token you obtained
281 when you authenticated. The token is encrypted with a key that only an
282 AFS File Server can know. If the File Server can decrypt your token, it
283 can communicate with your Cache Manager. In turn, the Cache Manager
284 accepts the File Server as genuine because the File Server can decrypt and use
285 the information in the token.
286 <A NAME="IDX787"></A>
287 <P><H3><A NAME="Header_21" HREF="auusg002.htm#ToC_21">Access Control Lists</A></H3>
288 <A NAME="IDX788"></A>
289 <P>AFS uses <I>access control lists</I> (<I>ACLs</I>) to determine who
290 can access the information in the AFS filespace. Each AFS directory has
291 an ACL to specify what actions different users can perform on that directory
292 and its files. An ACL can contain up to about 20 entries for users,
293 groups, or both; each entry lists a user or group and the permissions it
295 <P>The owner of a directory and system administrators can always administer an
296 ACL. Users automatically own their home directories and
297 subdirectories. Other non-owner users can define a directory's ACL
298 only if specifically granted that permission on the ACL. For more
299 information on ACLs, see <A HREF="auusg007.htm#HDRWQ44">Protecting Your Directories and Files</A>
301 <P>A group is composed of one or more users and client machines. If a
302 user belongs to a group that appears on an ACL, the user gets all of the
303 permissions granted to that group, just as if the user were listed directly on
304 the ACL. Similarly, if a user is logged into a client machine that
305 belongs to a group, the user has all of the permissions granted to that
306 group. For instructions on defining and using groups, see <A HREF="auusg008.htm#HDRWQ60">Using Groups</A>.
307 <P>All users who can access your cell's filespace, authenticated or not,
308 are automatically assigned to a group called
309 <B>system:anyuser</B>. For a discussion of placing the
310 <B>system:anyuser</B> group on ACLs, see <A HREF="auusg007.htm#HDRWQ51">Extending Access to Users from Foreign Cells</A>.
311 <TABLE><TR><TD ALIGN="LEFT" VALIGN="TOP"><B>Note:</B></TD><TD ALIGN="LEFT" VALIGN="TOP">You can use the UNIX mode bits to control access on specific files within an
312 AFS directory; however, the effect of these mode bits is different under
313 AFS than in the standard UNIX file system. See <A HREF="#HDRWQ16">File and Directory Protection</A>.
315 <HR><H2><A NAME="HDRWQ13" HREF="auusg002.htm#ToC_22">Differences Between UNIX and AFS</A></H2>
316 <P>AFS is designed to be similar to the UNIX file system.
317 For instance, many of the basic UNIX file manipulation commands (<B>cp</B>
318 for copy, <B>rm</B> for remove, and so on) are the same in AFS as they are
319 as in UNIX. All of your application programs work as they did
320 before. The following sections describe some of the differences between
321 a standard UNIX file system and AFS.
322 <P><H3><A NAME="HDRWQ14" HREF="auusg002.htm#ToC_23">File Sharing</A></H3>
323 <A NAME="IDX789"></A>
324 <A NAME="IDX790"></A>
325 <A NAME="IDX791"></A>
326 <P>AFS enables users to share remote files as easily as local files. To
327 access a file on a remote machine in AFS, you simply specify the file's
328 pathname. In contrast, to access a file in a remote machine's UNIX
329 file system, you must log into the remote machine or create a mount point on
330 the local machine that points to a directory in the remote machine's UNIX
332 <P>AFS users can see and share all the files under the <B>/afs</B> root
333 directory, given the appropriate privileges. An AFS user who has the
334 necessary privileges can access a file in any AFS cell, simply by specifying
335 the file's pathname. File sharing in AFS is not restricted by
336 geographical distances or operating system differences.
337 <P><H3><A NAME="HDRWQ15" HREF="auusg002.htm#ToC_24">Login and Authentication</A></H3>
338 <A NAME="IDX792"></A>
339 <P>To become an authenticated AFS user, you need to provide a password to
342 <P><LI>On machines that use an AFS-modified login utility, logging in is a
343 one-step process; your initial login automatically authenticates you with
345 <P><LI>On machines that do not use an AFS-modified login utility, you must
348 <P><LI>Log in to your local machine.
349 <P><LI>Issue the <B>klog</B> command with the <B>-setpag</B> argument to
350 authenticate with AFS and get your token.
353 <P>Your system administrator can tell you whether your machine uses an
354 AFS-modified login utility or not. Then see the login instructions in <A HREF="auusg005.htm#HDRWQ21">Logging in and Authenticating with AFS</A>.
355 <P>AFS authentication passwords are stored in special AFS database, rather
356 than in the local password file (<B>/etc/passwd</B> or equivalent).
357 If your machine uses an AFS-modified login utility, you can change your
358 password with a single command. If your machine does not use an
359 AFS-modified login utility, you must issue separate commands to change your
360 AFS and local passwords. See <A HREF="auusg005.htm#HDRWQ36">Changing Your Password</A>.
361 <A NAME="IDX793"></A>
362 <A NAME="IDX794"></A>
363 <A NAME="IDX795"></A>
364 <P><H3><A NAME="HDRWQ16" HREF="auusg002.htm#ToC_25">File and Directory Protection</A></H3>
365 <A NAME="IDX796"></A>
366 <A NAME="IDX797"></A>
367 <P>AFS does not rely on the mode bit protections of a standard UNIX system
368 (though its protection system does interact with these mode bits).
369 Instead, AFS uses an access control list (ACL) to control access to each
370 directory and its contents. The following list summarizes the
371 differences between the two methods:
373 <P><LI>UNIX mode bits specify three types of access permissions:
374 <B>r</B> (<B>read</B>), <B>w</B> (<B>write</B>), and
375 <B>x</B> (<B>execute</B>). An AFS ACL uses seven types of
376 permissions: <B>r</B> (<B>read</B>), <B>l</B>
377 (<B>lookup</B>), <B>i</B> (<B>insert</B>), <B>d</B>
378 (<B>delete</B>), <B>w</B> (<B>write</B>), <B>k</B>
379 (<B>lock</B>), and <B>a</B> (<B>administer</B>). For more
380 information, see <A HREF="auusg007.htm#HDRWQ46">The AFS ACL Permissions</A> and <A HREF="auusg007.htm#HDRWQ59">How AFS Uses the UNIX Mode Bits</A>.
381 <P><LI>The three sets of mode bits on each UNIX file or directory enable you to
382 grant permissions to three users or groups of users: the file or
383 directory's owner, the group that owns the file or directory, and all
384 other users. An ACL can accommodate up to about 20 entries, each of
385 which extends certain permissions to a user or group. Unlike standard
386 UNIX, a user can belong to an unlimited number of groups, and groups can be
387 defined by both users and system administrators. See <A HREF="auusg008.htm#HDRWQ60">Using Groups</A>.
388 <P><LI>UNIX mode bits are set individually on each file and directory. An
389 ACL applies to all of the files in a directory. While at first glance
390 the AFS method possibly seems less precise, in actuality (given a proper
391 directory structure) there are no major disadvantages to directory-level
392 protections and they are easier to establish and maintain.
394 <P><H3><A NAME="HDRWQ17" HREF="auusg002.htm#ToC_26">Machine Outages</A></H3>
395 <P>The kinds of failures you experience when a standard UNIX
396 file system goes down are different than when one or more individual AFS file
397 server machines become unavailable. When a standard UNIX file system is
398 inaccessible, the system simply locks up and you can lose changes to any files
399 with which you were working.
400 <P>When an AFS file server machine becomes inaccessible, you cannot access the
401 files on that machine. If a copy of the file is available from another
402 file server machine, however, you do not necessarily even notice the server
403 outage. This is because AFS gives your cell's system
404 administrators the ability to store copies of popular programs on multiple
405 file servers. The Cache Manager chooses between the copies
406 automatically; when one copy becomes unavailable, the Cache Manager
407 simply chooses another.
408 <P>If there are no other copies of a file that is stored on an inaccessible
409 server machine, you can usually continue to use the copy stored in your client
410 machine's local AFS cache. However, you cannot save changes to
411 files stored on an inaccessible file server machine until it is accessible
413 <P><H3><A NAME="HDRWQ18" HREF="auusg002.htm#ToC_27">Remote Commands</A></H3>
415 <A NAME="IDX798"></A>
416 <A NAME="IDX799"></A>
417 <A NAME="IDX800"></A>
418 <A NAME="IDX801"></A>
419 <A NAME="IDX802"></A>
420 <A NAME="IDX803"></A>
421 <A NAME="IDX804"></A>
422 <A NAME="IDX805"></A>
423 The UNIX <I>remote commands</I> enable you to run programs on a remote
424 machine without establishing a connection to it by using a program such as
425 <B>telnet</B>. Many of the remote commands (such as <B>ftp</B>,
426 <B>rcp</B>, and <B>rsh</B>) remain available in AFS, depending on how
427 your administrators have configured them. If the remote machine has a
428 Cache Manager, your token is used there also and you are authenticated while
429 the remote command runs. If the remote machine does not run a Cache
430 Manager, you receive the following message:
431 <PRE> Warning: unable to authenticate.
433 <P>In this case, you are logged into the remote machine's UNIX file
434 system, but you are not authenticated to AFS. You can access the local
435 files on the remote machine and the AFS directories that grant access to the
436 <B>system:anyuser</B> group, but you cannot access protected AFS
438 <P><H3><A NAME="Header_28" HREF="auusg002.htm#ToC_28">Differences in the Semantics of Standard UNIX Commands</A></H3>
439 <P>This section summarizes differences in the functionality of some
440 commonly issued UNIX commands.
443 <A NAME="IDX806"></A>
444 <A NAME="IDX807"></A>
445 </B><DD>Only members of the <B>system:administrators</B> group can use
446 this command to turn on the setuid, setgid or sticky mode bits on AFS
447 files. (For more information about this group, see <A HREF="auusg007.htm#HDRWQ50">Using the System Groups on ACLs</A>.)
449 <A NAME="IDX808"></A>
450 <A NAME="IDX809"></A>
451 </B><DD>Only members of the <B>system:administrators</B> group can issue
452 this command on AFS files.
454 <A NAME="IDX810"></A>
455 <A NAME="IDX811"></A>
456 </B><DD>Only members of the <B>system:administrators</B> group can issue
457 this command on AFS files and directories.
459 <A NAME="IDX812"></A>
460 <A NAME="IDX813"></A>
461 </B><DD>If the user's AFS tokens are identified by a process authentication
462 group (PAG), the output of this command includes two large numbers. For
463 a description of PAGs, see <A HREF="auusg005.htm#HDRWQ24">Authenticating with AFS</A>.
465 <A NAME="IDX814"></A>
466 <A NAME="IDX815"></A>
467 </B><DD>The AFS version of this daemon authenticates remote issuers of the
468 AFS-modified <B>rcp</B> and <B>rsh</B> commands with AFS.
469 <P><DT><B>login utilities
470 <A NAME="IDX816"></A>
471 </B><DD>AFS-modified login utilities both log you into the local UNIX file system
472 and authenticate you with AFS.
474 <A NAME="IDX817"></A>
475 <A NAME="IDX818"></A>
476 </B><DD>You cannot use this command to create a hard link between files that
477 reside in different AFS directories. You must add the <B>-s</B>
478 option to create a symbolic link instead.
480 <HR><H2><A NAME="HDRWQ19" HREF="auusg002.htm#ToC_29">Using AFS with NFS</A></H2>
481 <P>Some cells use the Networking File System (NFS) in addition
482 to AFS. If you work on an NFS client machine, your system administrator
483 can configure it to access the AFS filespace through a program called the
484 <I>NFS/AFS Translator</I><SUP>TM</SUP>. See <A HREF="auusg010.htm#HDRWQ80">Appendix A, Using the NFS/AFS Translator</A>.
485 <HR><P ALIGN="center"> <A HREF="../index.htm"><IMG SRC="../books.gif" BORDER="0" ALT="[Return to Library]"></A> <A HREF="auusg002.htm#ToC"><IMG SRC="../toc.gif" BORDER="0" ALT="[Contents]"></A> <A HREF="auusg003.htm"><IMG SRC="../prev.gif" BORDER="0" ALT="[Previous Topic]"></A> <A HREF="#Top_Of_Page"><IMG SRC="../top.gif" BORDER="0" ALT="[Top of Topic]"></A> <A HREF="auusg005.htm"><IMG SRC="../next.gif" BORDER="0" ALT="[Next Topic]"></A> <A HREF="auusg013.htm#HDRINDEX"><IMG SRC="../index.gif" BORDER="0" ALT="[Index]"></A> <P>
486 <!-- Begin Footer Records ========================================== -->
488 <br>© <A HREF="http://www.ibm.com/">IBM Corporation 2000.</A> All Rights Reserved
490 <!-- End Footer Records ============================================ -->
491 <A NAME="Bot_Of_Page"></A>
git://git.openafs.org / openafs.git / blob