This is am-utils.info, produced by makeinfo version 4.1 from am-utils.texi. START-INFO-DIR-ENTRY * Am-utils: (am-utils). The Amd automounter suite of utilities END-INFO-DIR-ENTRY  File: am-utils.info, Node: Top, Next: License, Up: (DIR) Am-utils - The 4.4BSD Automounter Tool Suite ********************************************* Am-utils is the 4.4BSD Automounter Tool Suite, which includes the Amd automounter, the Amq query and control program, the Hlfsd daemon, and other tools. This Info file describes how to use and understand the tools within Am-utils. * Menu: * License:: Explains the terms and conditions for using and distributing Am-utils. * Distrib:: How to get the latest Am-utils distribution. * Intro:: An introduction to Automounting concepts. * History:: History of am-utils' development. * Overview:: An overview of Amd. * Supported Platforms:: Machines and Systems supported by Amd. * Mount Maps:: Details of mount maps * Amd Command Line Options:: All the Amd command line options explained. * Filesystem Types:: The different mount types supported by Amd. * Amd Configuration File:: The amd.conf file syntax and meaning. * Run-time Administration:: How to start, stop and control Amd. * FSinfo:: The FSinfo filesystem management tool. * Hlfsd:: The Home-Link Filesystem server. * Assorted Tools:: Other tools which come with am-utils. * Examples:: Some examples showing how Amd might be used. * Internals:: Implementation details. * Acknowledgments & Trademarks:: Legal Notes Indexes * Index:: An item for each concept.  File: am-utils.info, Node: License, Next: Distrib, Prev: Top, Up: Top License ******* Am-utils is not in the public domain; it is copyrighted and there are restrictions on its distribution. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. All advertising materials mentioning features or use of this software must display the following acknowledgment: "This product includes software developed by the University of California, Berkeley and its contributors, as well as the Trustees of Columbia University." 4. Neither the name of the University nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  File: am-utils.info, Node: Distrib, Next: Intro, Prev: License, Up: Top Source Distribution ******************* The Am-utils home page is located in You can get the latest distribution version of Am-utils from Additional alpha, beta, and release distributions are available in . Revision 5.2 was part of the 4.3BSD Reno distribution. Revision 5.3bsdnet, a late alpha version of 5.3, was part of the BSD network version 2 distribution Revision 6.0 was made independently by Erez Zadok at the Computer Science Department (http://www.cs.columbia.edu/) of Columbia University (http://www.columbia.edu/), as part of his PhD thesis work (http://www.cs.columbia.edu/~ezk/research/tp/thesis_proposal.html). *Note History::, for more details. Bug Reports =========== Before reporting a bug, see if it is a known one in the bugs (http://www.am-utils.org/BUGS.txt) file. Send all bug reports to quoting the details of the release and your configuration. These can be obtained by running the command `amd -v'. It would greatly help if you could provide a reproducible procedure for detecting the bug you are reporting. Providing working patches is highly encouraged. Every patch incorporated, however small, will get its author an honorable mention in the authors file (http://www.am-utils.org/AUTHORS.txt). Mailing List ============ There are two mailing lists for people interested in keeping up-to-date with developments. 1. The older list, `amd-workers' is for general "how to" questions and announcements. To subscribe, send a note to .(1) To post a message to this list, send mail to . 2. The developers only list, `amd-dev' is for - announcements of alpha and beta releases of am-utils - reporting of bugs and patches - discussions of new features for am-utils - implementation and porting issues To subscribe, send a note to with the single body text line `subscribe amd-dev'. To post a message to this list, send mail to . To avoid as much spam as possible, only subscribers to this list may post to it. Subscribers of `amd-dev' are most suitable if they have the time and resources to test new and buggy versions of amd, on as many different platforms as possible. They should also be prepared to learn and use the GNU Autoconf, Automake, and Libtool packages, and of course, be very familiar with the complex code in the am-utils package. In other words, subscribers on this list should be able to contribute meaningfully to the development of amd. ---------- Footnotes ---------- (1) Note that the older address, , is defunct.  File: am-utils.info, Node: Intro, Next: History, Prev: Distrib, Up: Top Introduction ************ An "automounter" maintains a cache of mounted filesystems. Filesystems are mounted on demand when they are first referenced, and unmounted after a period of inactivity. Amd may be used as a replacement for Sun's automounter. The choice of which filesystem to mount can be controlled dynamically with "selectors". Selectors allow decisions of the form "hostname is THIS," or "architecture is not THAT." Selectors may be combined arbitrarily. Amd also supports a variety of filesystem types, including NFS, UFS and the novel "program" filesystem. The combination of selectors and multiple filesystem types allows identical configuration files to be used on all machines thus reducing the administrative overhead. Amd ensures that it will not hang if a remote server goes down. Moreover, Amd can determine when a remote server has become inaccessible and then mount replacement filesystems as and when they become available. Amd contains no proprietary source code and has been ported to numerous flavors of Unix.  File: am-utils.info, Node: History, Next: Overview, Prev: Intro, Up: Top History ******* The Amd package has been without an official maintainer since 1992. Several people have stepped in to maintain it unofficially. Most notable were the `upl' (Unofficial Patch Level) releases of Amd, created by me (Erez Zadok ), and available from . The last such unofficial release was `upl102'. Through the process of patching and aging, it was becoming more and more apparent that Amd was in much need of revitalizing. Maintaining Amd had become a difficult task. I took it upon myself to cleanup the code, so that it would be easier to port to new platforms, add new features, keep up with the many new feature requests, and deal with the never ending stream of bug reports. I have been working on such a release of Amd on and off since January of 1996. The new suite of tools is currently named "am-utils" (AutoMounter Utilities), in line with GNU naming conventions, befitting the contents of the package. In October of 1996 I had received enough offers to help me with this task that I decided to make a mailing list for this group of people. Around the same time, Amd had become a necessary part of my PhD thesis work, resulting in more work performed on am-utils. Am-utils version 6.0 was numbered with a major new release number to distinguish it from the last official release of Amd (5.x). Many new features have been added such as a GNU `configure' system, NFS Version 3, a run-time configuration file (`amd.conf'), many new ports, more scripts and programs, as well as numerous bug fixes. Another reason for the new major release number was to alert users of am-utils that user-visible interfaces may have changed. In order to make Amd work well for the next 10 years, and be easier to maintain, it was necessary to remove old or unused features, change various syntax files, etc. However, great care was taken to ensure the maximum possible backwards compatibility.  File: am-utils.info, Node: Overview, Next: Supported Platforms, Prev: History, Up: Top Overview ******** Amd maintains a cache of mounted filesystems. Filesystems are "demand-mounted" when they are first referenced, and unmounted after a period of inactivity. Amd may be used as a replacement for Sun's automount(8) program. It contains no proprietary source code and has been ported to numerous flavors of Unix. *Note Supported Platforms::. Amd was designed as the basis for experimenting with filesystem layout and management. Although Amd has many direct applications it is loaded with additional features which have little practical use. At some point the infrequently used components may be removed to streamline the production system. * Menu: * Fundamentals:: * Filesystems and Volumes:: * Volume Naming:: * Volume Binding:: * Operational Principles:: * Mounting a Volume:: * Automatic Unmounting:: * Keep-alives:: * Non-blocking Operation::  File: am-utils.info, Node: Fundamentals, Next: Filesystems and Volumes, Prev: Overview, Up: Overview Fundamentals ============ The fundamental concept behind Amd is the ability to separate the name used to refer to a file from the name used to refer to its physical storage location. This allows the same files to be accessed with the same name regardless of where in the network the name is used. This is very different from placing `/n/hostname' in front of the pathname since that includes location dependent information which may change if files are moved to another machine. By placing the required mappings in a centrally administered database, filesystems can be re-organized without requiring changes to configuration files, shell scripts and so on.  File: am-utils.info, Node: Filesystems and Volumes, Next: Volume Naming, Prev: Fundamentals, Up: Overview Filesystems and Volumes ======================= Amd views the world as a set of fileservers, each containing one or more filesystems where each filesystem contains one or more "volumes". Here the term "volume" is used to refer to a coherent set of files such as a user's home directory or a TeX distribution. In order to access the contents of a volume, Amd must be told in which filesystem the volume resides and which host owns the filesystem. By default the host is assumed to be local and the volume is assumed to be the entire filesystem. If a filesystem contains more than one volume, then a "sublink" is used to refer to the sub-directory within the filesystem where the volume can be found.  File: am-utils.info, Node: Volume Naming, Next: Volume Binding, Prev: Filesystems and Volumes, Up: Overview Volume Naming ============= Volume names are defined to be unique across the entire network. A volume name is the pathname to the volume's root as known by the users of that volume. Since this name uniquely identifies the volume contents, all volumes can be named and accessed from each host, subject to administrative controls. Volumes may be replicated or duplicated. Replicated volumes contain identical copies of the same data and reside at two or more locations in the network. Each of the replicated volumes can be used interchangeably. Duplicated volumes each have the same name but contain different, though functionally identical, data. For example, `/vol/tex' might be the name of a TeX distribution which varied for each machine architecture. Amd provides facilities to take advantage of both replicated and duplicated volumes. Configuration options allow a single set of configuration data to be shared across an entire network by taking advantage of replicated and duplicated volumes. Amd can take advantage of replacement volumes by mounting them as required should an active fileserver become unavailable.  File: am-utils.info, Node: Volume Binding, Next: Operational Principles, Prev: Volume Naming, Up: Overview Volume Binding ============== Unix implements a namespace of hierarchically mounted filesystems. Two forms of binding between names and files are provided. A "hard link" completes the binding when the name is added to the filesystem. A "soft link" delays the binding until the name is accessed. An "automounter" adds a further form in which the binding of name to filesystem is delayed until the name is accessed. The target volume, in its general form, is a tuple (host, filesystem, sublink) which can be used to name the physical location of any volume in the network. When a target is referenced, Amd ignores the sublink element and determines whether the required filesystem is already mounted. This is done by computing the local mount point for the filesystem and checking for an existing filesystem mounted at the same place. If such a filesystem already exists then it is assumed to be functionally identical to the target filesystem. By default there is a one-to-one mapping between the pair (host, filesystem) and the local mount point so this assumption is valid.  File: am-utils.info, Node: Operational Principles, Next: Mounting a Volume, Prev: Volume Binding, Up: Overview Operational Principles ====================== Amd operates by introducing new mount points into the namespace. These are called "automount" points. The kernel sees these automount points as NFS filesystems being served by Amd. Having attached itself to the namespace, Amd is now able to control the view the rest of the system has of those mount points. RPC calls are received from the kernel one at a time. When a "lookup" call is received Amd checks whether the name is already known. If it is not, the required volume is mounted. A symbolic link pointing to the volume root is then returned. Once the symbolic link is returned, the kernel will send all other requests direct to the mounted filesystem. If a volume is not yet mounted, Amd consults a configuration "mount-map" corresponding to the automount point. Amd then makes a runtime decision on what and where to mount a filesystem based on the information obtained from the map. Amd does not implement all the NFS requests; only those relevant to name binding such as "lookup", "readlink" and "readdir". Some other calls are also implemented but most simply return an error code; for example "mkdir" always returns "read-only filesystem".  File: am-utils.info, Node: Mounting a Volume, Next: Automatic Unmounting, Prev: Operational Principles, Up: Overview Mounting a Volume ================= Each automount point has a corresponding mount map. The mount map contains a list of key-value pairs. The key is the name of the volume to be mounted. The value is a list of locations describing where the filesystem is stored in the network. In the source for the map the value would look like location1 location2 ... locationN Amd examines each location in turn. Each location may contain "selectors" which control whether Amd can use that location. For example, the location may be restricted to use by certain hosts. Those locations which cannot be used are ignored. Amd attempts to mount the filesystem described by each remaining location until a mount succeeds or Amd can no longer proceed. The latter can occur in three ways: * If none of the locations could be used, or if all of the locations caused an error, then the last error is returned. * If a location could be used but was being mounted in the background then Amd marks that mount as being "in progress" and continues with the next request; no reply is sent to the kernel. * Lastly, one or more of the mounts may have been "deferred". A mount is deferred if extra information is required before the mount can proceed. When the information becomes available the mount will take place, but in the mean time no reply is sent to the kernel. If the mount is deferred, Amd continues to try any remaining locations. Once a volume has been mounted, Amd establishes a "volume mapping" which is used to satisfy subsequent requests.  File: am-utils.info, Node: Automatic Unmounting, Next: Keep-alives, Prev: Mounting a Volume, Up: Overview Automatic Unmounting ==================== To avoid an ever increasing number of filesystem mounts, Amd removes volume mappings which have not been used recently. A time-to-live interval is associated with each mapping and when that expires the mapping is removed. When the last reference to a filesystem is removed, that filesystem is unmounted. If the unmount fails, for example the filesystem is still busy, the mapping is re-instated and its time-to-live interval is extended. The global default for this grace period is controlled by the `-w' command-line option (*note -w: -w Option.) or the amd.conf parameter `dismount_interval' (*note dismount_interval Parameter::). It is also possible to set this value on a per-mount basis (*note opts: opts Option.). Filesystems can be forcefully timed out using the Amq command. *Note Run-time Administration::.  File: am-utils.info, Node: Keep-alives, Next: Non-blocking Operation, Prev: Automatic Unmounting, Up: Overview Keep-alives =========== Use of some filesystem types requires the presence of a server on another machine. If a machine crashes then it is of no concern to processes on that machine that the filesystem is unavailable. However, to processes on a remote host using that machine as a fileserver this event is important. This situation is most widely recognized when an NFS server crashes and the behavior observed on client machines is that more and more processes hang. In order to provide the possibility of recovery, Amd implements a "keep-alive" interval timer for some filesystem types. Currently only NFS makes use of this service. The basis of the NFS keep-alive implementation is the observation that most sites maintain replicated copies of common system data such as manual pages, most or all programs, system source code and so on. If one of those servers goes down it would be reasonable to mount one of the others as a replacement. The first part of the process is to keep track of which fileservers are up and which are down. Amd does this by sending RPC requests to the servers' NFS `NullProc' and checking whether a reply is returned. While the server state is uncertain the requests are re-transmitted at three second intervals and if no reply is received after four attempts the server is marked down. If a reply is received the fileserver is marked up and stays in that state for 30 seconds at which time another NFS ping is sent. Once a fileserver is marked down, requests continue to be sent every 30 seconds in order to determine when the fileserver comes back up. During this time any reference through Amd to the filesystems on that server fail with the error "Operation would block". If a replacement volume is available then it will be mounted, otherwise the error is returned to the user. Although this action does not protect user files, which are unique on the network, or processes which do not access files via Amd or already have open files on the hung filesystem, it can prevent most new processes from hanging.  File: am-utils.info, Node: Non-blocking Operation, Prev: Keep-alives, Up: Overview Non-blocking Operation ====================== Since there is only one instance of Amd for each automount point, and usually only one instance on each machine, it is important that it is always available to service kernel calls. Amd goes to great lengths to ensure that it does not block in a system call. As a last resort Amd will fork before it attempts a system call that may block indefinitely, such as mounting an NFS filesystem. Other tasks such as obtaining filehandle information for an NFS filesystem, are done using a purpose built non-blocking RPC library which is integrated with Amd's task scheduler. This library is also used to implement NFS keep-alives (*note Keep-alives::). Whenever a mount is deferred or backgrounded, Amd must wait for it to complete before replying to the kernel. However, this would cause Amd to block waiting for a reply to be constructed. Rather than do this, Amd simply "drops" the call under the assumption that the kernel RPC mechanism will automatically retry the request.  File: am-utils.info, Node: Supported Platforms, Next: Mount Maps, Prev: Overview, Up: Top Supported Platforms ******************* Am-utils has been ported to a wide variety of machines and operating systems. Am-utils's code works for little-endian and big-endian machines, as well as 32 bit and 64 bit architectures. Furthermore, when Am-utils ports to an Operating System on one architecture, it is generally readily portable to the same Operating System on all platforms on which it is available. The table below lists those platforms supported by the latest release. The listing is based on the standard output from GNU's `config.guess' script. Since significant changes have been made to am-utils, not all systems listed here have been verified working for all features. Auto-Configured System Name Config Compile Amd NFS3 Shlib Hlfsd alpha-dec-osf2.1 yes yes yes ? no ? alpha-dec-osf4.0 yes yes yes yes yes ? alpha-dec-osf4.0f yes yes yes yes yes ? alpha-dec-osf5.1 yes yes yes yes yes ? alphaev5-unknown-linux-gnu yes yes yes n/a yes ? alphaev5-unknown-linux-gnu-rh5.2yes yes yes n/a yes ? alphaev6-dec-osf5.0 yes yes yes yes yes ? hppa1.0-hp-hpux11.00 yes yes yes no yes yes hppa1.1-hp-hpux10.10 yes yes yes n/a no ? hppa1.1-hp-hpux10.20 yes yes yes no no ? hppa1.1-hp-hpux11.00 yes yes yes UDP yes yes hppa1.1-hp-hpux9.01 yes yes yes n/a yes ? hppa1.1-hp-hpux9.05 yes yes yes n/a yes ? hppa1.1-hp-hpux9.07 yes yes yes n/a yes ? hppa2.0w-hp-hpux11.00 yes yes yes n/a yes ? i386-pc-bsdi2.1 yes yes yes n/a no ? i386-pc-bsdi3.0 yes yes yes yes no ? i386-pc-bsdi3.1 yes yes yes yes no ? i386-pc-bsdi4.0 yes yes yes yes yes ? i386-pc-bsdi4.0.1 yes yes yes yes yes ? i386-pc-bsdi4.1 yes yes yes yes yes ? i386-pc-linux-rh7.2 yes yes yes yes yes yes i386-pc-solaris2.5.1 yes yes yes yes yes yes i386-pc-solaris2.6 yes yes yes yes yes yes i386-pc-solaris2.7 yes yes yes yes yes yes i386-unknown-freebsd2.1.0 yes yes yes n/a ? ? i386-unknown-freebsd2.2.1 yes yes yes n/a yes ? i386-unknown-freebsd2.2.6 yes yes yes n/a yes ? i386-unknown-freebsd2.2.7 yes yes yes n/a yes ? i386-unknown-freebsd2.2.8 yes yes yes n/a yes ? i386-unknown-freebsd3.0 yes yes yes yes yes ? i386-unknown-freebsd4.2 yes yes yes yes yes ? i386-unknown-freebsd4.4 yes yes yes yes yes ? i386-unknown-freebsd5.0 yes yes yes yes yes ? i386-unknown-freebsdelf3.0 yes yes yes yes yes ? i386-unknown-freebsdelf3.1 yes yes yes yes yes ? i386-unknown-freebsdelf3.2 yes yes yes yes yes ? i386-unknown-freebsdelf3.3 yes yes yes yes yes ? i386-unknown-freebsdelf3.4 yes yes yes yes yes ? i386-unknown-freebsdelf4.0 yes yes yes yes yes ? i386-unknown-netbsd1.2.1 yes yes yes yes yes ? i386-unknown-netbsd1.3 yes yes yes yes yes ? i386-unknown-netbsd1.3.1 yes yes yes yes yes ? i386-unknown-netbsd1.3.2 yes yes yes yes yes ? i386-unknown-netbsd1.3.3 yes yes yes yes yes ? i386-unknown-netbsd1.4 yes yes yes yes yes ? i386-unknown-netbsd1.4.1 yes yes yes yes yes ? i386-unknown-openbsd2.1 yes yes yes yes yes ? i386-unknown-openbsd2.2 yes yes yes yes yes ? i386-unknown-openbsd2.3 yes yes yes yes yes ? i386-unknown-openbsd2.4 yes yes yes yes yes ? i386-unknown-openbsd2.5 yes yes yes yes yes ? i486-ncr-sysv4.3.03 yes yes ? yes yes ? i486-pc-linux-gnu-rh6.0 yes yes yes n/a yes ? i486-pc-linux-gnulibc1 yes yes yes n/a yes ? i486-pc-linux-gnulibc1-rh4.2 yes yes yes n/a yes ? i486-pc-linux-gnuoldld yes yes yes n/a yes ? i586-pc-linux-gnu yes yes yes n/a yes ? i586-pc-linux-gnu-rh5.2 yes yes yes n/a yes ? i586-pc-linux-gnu-rh6.0 yes yes yes n/a yes ? i586-pc-linux-gnu-rh6.1 yes yes yes n/a yes ? i586-pc-linux-gnu-rh6.2 yes yes yes n/a yes ? i586-pc-linux-gnulibc1 yes yes yes n/a yes ? i586-pc-linux-gnulibc1-rh4.2 yes yes yes n/a yes ? i686-pc-linux-gnu yes yes yes n/a yes ? i686-pc-linux-gnu-rh5.2 yes yes yes n/a yes ? i686-pc-linux-gnu-rh6.0 yes yes yes n/a yes ? i686-pc-linux-gnu-rh6.2 yes yes yes n/a yes yes i686-pc-linux-gnulibc yes yes yes n/a yes ? i686-pc-linux-gnulibc1 yes yes yes n/a yes ? ia64-hp-hpux11.20 yes yes yes yes yes ? ia64-unknown-linux-rh7.1 yes yes yes yes yes yes m68k-hp-hpux9.00 yes yes yes n/a ? ? m68k-sun-sunos4.1.1 yes yes yes n/a no ? m68k-next-nextstep3 yes yes yes n/a no ? mips-dec-ultrix4.3 yes yes yes n/a ? ? mips-sgi-irix5.2 ? ? ? ? ? ? mips-sgi-irix5.3 yes yes yes yes yes ? mips-sgi-irix6.2 yes yes yes yes yes ? mips-sgi-irix6.4 yes yes yes yes yes ? mips-sgi-irix6.5 yes yes yes yes yes ? powerpc-ibm-aix4.1.5.0 yes yes yes n/a no/broken? powerpc-ibm-aix4.2.1.0 yes yes yes yes no/broken? powerpc-ibm-aix4.3.1.0 yes yes ? yes ? ? powerpc-unknown-linux-gnu yes yes yes n/a yes ? rs6000-ibm-aix3.2 yes yes yes n/a ? ? rs6000-ibm-aix3.2.5 yes yes yes n/a ? ? rs6000-ibm-aix4.1.4.0 yes yes yes n/a no/broken? rs6000-ibm-aix4.1.5.0 yes yes yes n/a no/broken? sparc-sun-solaris2.3 yes yes yes n/a yes ? sparc-sun-solaris2.4 yes yes yes n/a yes ? sparc-sun-solaris2.5 yes yes yes yes yes ? sparc-sun-solaris2.5.1 yes yes yes yes yes yes sparc-sun-solaris2.6 yes yes yes yes yes yes sparc-sun-solaris2.7 yes yes yes yes yes yes sparc-sun-solaris2.8 yes yes yes yes yes yes sparc-sun-sunos4.1.1 yes yes yes n/a yes ? sparc-sun-sunos4.1.3 yes yes yes n/a yes ? sparc-sun-sunos4.1.3C yes yes yes n/a yes ? sparc-sun-sunos4.1.3_U1 yes yes yes n/a yes ? sparc-sun-sunos4.1.4 yes yes yes n/a yes ? sparc-unknown-linux-gnulibc1 yes yes yes n/a yes ? sparc-unknown-netbsd1.2E yes yes yes ? ? ? sparc-unknown-netbsd1.2G yes yes yes ? ? ? sparc64-unknown-linux-gnu yes yes yes n/a yes ? See the `INSTALL' in the distribution for more specific details on building and/or configuring for some systems.  File: am-utils.info, Node: Mount Maps, Next: Amd Command Line Options, Prev: Supported Platforms, Up: Top Mount Maps ********** Amd has no built-in knowledge of machines or filesystems. External "mount-maps" are used to provide the required information. Specifically, Amd needs to know when and under what conditions it should mount filesystems. The map entry corresponding to the requested name contains a list of possible locations from which to resolve the request. Each location specifies filesystem type, information required by that filesystem (for example the block special device in the case of UFS), and some information describing where to mount the filesystem (*note fs Option::). A location may also contain "selectors" (*note Selectors::). * Menu: * Map Types:: * Key Lookup:: * Location Format::  File: am-utils.info, Node: Map Types, Next: Key Lookup, Prev: Mount Maps, Up: Mount Maps Map Types ========= A mount-map provides the run-time configuration information to Amd. Maps can be implemented in many ways. Some of the forms supported by Amd are regular files, ndbm databases, NIS maps, the "Hesiod" name server, and even the password file. A mount-map "name" is a sequence of characters. When an automount point is created a handle on the mount-map is obtained. For each map type configured, Amd attempts to reference the map of the appropriate type. If a map is found, Amd notes the type for future use and deletes the reference, for example closing any open file descriptors. The available maps are configured when Amd is built and can be displayed by running the command `amd -v'. When using an Amd configuration file (*note Amd Configuration File::) and the keyword `map_type' (*note map_type Parameter::), you may force the map used to any type. By default, Amd caches data in a mode dependent on the type of map. This is the same as specifying `cache:=mapdefault' and selects a suitable default cache mode depending on the map type. The individual defaults are described below. The CACHE option can be specified on automount points to alter the caching behavior (*note Automount Filesystem::). The following map types have been implemented, though some are not available on all machines. Run the command `amd -v' to obtain a list of map types configured on your machine. * Menu: * File maps:: * ndbm maps:: * NIS maps:: * NIS+ maps:: * Hesiod maps:: * Password maps:: * Union maps:: * LDAP maps::  File: am-utils.info, Node: File maps, Next: ndbm maps, Prev: Map Types, Up: Map Types File maps --------- When Amd searches a file for a map entry it does a simple scan of the file and supports both comments and continuation lines. Continuation lines are indicated by a backslash character (`\') as the last character of a line in the file. The backslash, newline character _and any leading white space on the following line_ are discarded. A maximum line length of 2047 characters is enforced after continuation lines are read but before comments are stripped. Each line must end with a newline character; that is newlines are terminators, not separators. The following examples illustrate this: key valA valB; \ valC specifies _three_ locations, and is identical to key valA valB; valC However, key valA valB;\ valC specifies only _two_ locations, and is identical to key valA valB;valC After a complete line has been read from the file, including continuations, Amd determines whether there is a comment on the line. A comment begins with a hash ("`#'") character and continues to the end of the line. There is no way to escape or change the comment lead-in character. Note that continuation lines and comment support "only" apply to file maps, or ndbm maps built with the `mk-amd-map' program. When caching is enabled, file maps have a default cache mode of `all' (*note Automount Filesystem::).  File: am-utils.info, Node: ndbm maps, Next: NIS maps, Prev: File maps, Up: Map Types ndbm maps --------- An ndbm map may be used as a fast access form of a file map. The program, `mk-amd-map', converts a normal map file into an ndbm database. This program supports the same continuation and comment conventions that are provided for file maps. Note that ndbm format files may _not_ be sharable across machine architectures. The notion of speed generally only applies to large maps; a small map, less than a single disk block, is almost certainly better implemented as a file map. ndbm maps have a default cache mode of `all' (*note Automount Filesystem::).  File: am-utils.info, Node: NIS maps, Next: NIS+ maps, Prev: ndbm maps, Up: Map Types NIS maps -------- When using NIS (formerly YP), an Amd map is implemented directly by the underlying NIS map. Comments and continuation lines are _not_ supported in the automounter and must be stripped when constructing the NIS server's database. NIS maps have a default cache mode of `all' (*note Automount Filesystem::). The following rule illustrates what could be added to your NIS `Makefile', in this case causing the `amd.home' map to be rebuilt: $(YPTSDIR)/amd.home.time: $(ETCDIR)/amd.home -@sed -e "s/#.*$$//" -e "/^$$/d" $(ETCDIR)/amd.home | \ awk '{ \ for (i = 1; i <= NF; i++) \ if (i == NF) { \ if (substr($$i, length($$i), 1) == "\\") \ printf("%s", substr($$i, 1, length($$i) - 1)); \ else \ printf("%s\n", $$i); \ } \ else \ printf("%s ", $$i); \ }' | \ $(MAKEDBM) - $(YPDBDIR)/amd.home; \ touch $(YPTSDIR)/amd.home.time; \ echo "updated amd.home"; \ if [ ! $(NOPUSH) ]; then \ $(YPPUSH) amd.home; \ echo "pushed amd.home"; \ else \ : ; \ fi Here `$(YPTSDIR)' contains the time stamp files, and `$(YPDBDIR)' contains the dbm format NIS files.  File: am-utils.info, Node: NIS+ maps, Next: Hesiod maps, Prev: NIS maps, Up: Map Types NIS+ maps --------- NIS+ maps do not support cache mode `all' and, when caching is enabled, have a default cache mode of `inc'. XXX: FILL IN WITH AN EXAMPLE.  File: am-utils.info, Node: Hesiod maps, Next: Password maps, Prev: NIS+ maps, Up: Map Types Hesiod maps ----------- When the map name begins with the string `hesiod.' lookups are made using the "Hesiod" name server. The string following the dot is used as a name qualifier and is prepended with the key being located. The entire string is then resolved in the `automount' context, or the amd.conf parameter `hesiod_base' (*note hesiod_base Parameter::). For example, if the key is `jsp' and map name is `hesiod.homes' then "Hesiod" is asked to resolve `jsp.homes.automount'. Hesiod maps do not support cache mode `all' and, when caching is enabled, have a default cache mode of `inc' (*note Automount Filesystem::). The following is an example of a "Hesiod" map entry: jsp.homes.automount HS TXT "rfs:=/home/charm;rhost:=charm;sublink:=jsp" njw.homes.automount HS TXT "rfs:=/home/dylan/dk2;rhost:=dylan;sublink:=njw"  File: am-utils.info, Node: Password maps, Next: Union maps, Prev: Hesiod maps, Up: Map Types Password maps ------------- The password map support is unlike the four previous map types. When the map name is the string `/etc/passwd' Amd can lookup a user name in the password file and re-arrange the home directory field to produce a usable map entry. Amd assumes the home directory has the format `/anydir/dom1/../domN/login'. It breaks this string into a map entry where `${rfs}' has the value `/anydir/domN', `${rhost}' has the value `domN.....dom1', and `${sublink}' has the value login. Thus if the password file entry was /home/achilles/jsp the map entry used by Amd would be rfs:=/home/achilles;rhost:=achilles;sublink:=jsp Similarly, if the password file entry was /home/cc/sugar/mjh the map entry used by Amd would be rfs:=/home/sugar;rhost:=sugar.cc;sublink:=jsp  File: am-utils.info, Node: Union maps, Next: LDAP maps, Prev: Password maps, Up: Map Types Union maps ---------- The union map support is provided specifically for use with the union filesystem, *note Union Filesystem::. It is identified by the string `union:' which is followed by a colon separated list of directories. The directories are read in order, and the names of all entries are recorded in the map cache. Later directories take precedence over earlier ones. The union filesystem type then uses the map cache to determine the union of the names in all the directories.  File: am-utils.info, Node: LDAP maps, Prev: Union maps, Up: Map Types LDAP maps --------- LDAP (Lightweight Directory Access Protocol) maps do not support cache mode `all' and, when caching is enabled, have a default cache mode of `inc'. For example, an Amd map `amd.home' that looks as follows: /defaults opts:=rw,intr;type:=link zing -rhost:=shekel \ host==shekel \ host!=shekel;type:=nfs when converted to LDAP (*note amd2ldif::), will result in the following LDAP database: $ amd2ldif amd.home CUCS < amd.home dn: cn=amdmap timestamp, CUCS cn : amdmap timestamp objectClass : amdmapTimestamp amdmapTimestamp: 873071363 dn: cn=amdmap amd.home[/defaults], CUCS cn : amdmap amd.home[/defaults] objectClass : amdmap amdmapName : amd.home amdmapKey : /defaults amdmapValue : opts:=rw,intr;type:=link dn: cn=amdmap amd.home[], CUCS cn : amdmap amd.home[] objectClass : amdmap amdmapName : amd.home amdmapKey : amdmapValue : dn: cn=amdmap amd.home[zing], CUCS cn : amdmap amd.home[zing] objectClass : amdmap amdmapName : amd.home amdmapKey : zing amdmapValue : -rhost:=shekel host==shekel host!=shekel;type:=nfs  File: am-utils.info, Node: Key Lookup, Next: Location Format, Prev: Map Types, Up: Mount Maps How keys are looked up ====================== The key is located in the map whose type was determined when the automount point was first created. In general the key is a pathname component. In some circumstances this may be modified by variable expansion (*note Variable Expansion::) and prefixing. If the automount point has a prefix, specified by the PREF option, then that is prepended to the search key before the map is searched. If the map cache is a `regexp' cache then the key is treated as an egrep-style regular expression, otherwise a normal string comparison is made. If the key cannot be found then a "wildcard" match is attempted. Amd repeatedly strips the basename from the key, appends `/*' and attempts a lookup. Finally, Amd attempts to locate the special key `*'. For example, the following sequence would be checked if `home/dylan/dk2' was being located: home/dylan/dk2 home/dylan/* home/* * At any point when a wildcard is found, Amd proceeds as if an exact match had been found and the value field is then used to resolve the mount request, otherwise an error code is propagated back to the kernel. (*note Filesystem Types::).  File: am-utils.info, Node: Location Format, Prev: Key Lookup, Up: Mount Maps Location Format =============== The value field from the lookup provides the information required to mount a filesystem. The information is parsed according to the syntax shown below. location-list: location-selection location-list white-space || white-space location-selection location-selection: location location-selection white-space location location: location-info -location-info - location-info: sel-or-opt location-info;sel-or-opt ; sel-or-opt: selection opt-ass selection: selector==value selector!=value opt-ass: option:=value white-space: space tab Note that unquoted whitespace is not allowed in a location description. White space is only allowed, and is mandatory, where shown with non-terminal white-space. A "location-selection" is a list of possible volumes with which to satisfy the request. "location-selection"s are separated by the `||' operator. The effect of this operator is to prevent use of location-selections to its right if any of the location-selections on its left were selected whether or not any of them were successfully mounted (*note Selectors::). The location-selection, and singleton "location-list", `type:=ufs;dev:=/dev/xd1g' would inform Amd to mount a UFS filesystem from the block special device `/dev/xd1g'. The "sel-or-opt" component is either the name of an option required by a specific filesystem, or it is the name of a built-in, predefined selector such as the architecture type. The value may be quoted with double quotes `"', for example `type:="ufs";dev:="/dev/xd1g"'. These quotes are stripped when the value is parsed and there is no way to get a double quote into a value field. Double quotes are used to get white space into a value field, which is needed for the program filesystem (*note Program Filesystem::). * Menu: * Map Defaults:: * Variable Expansion:: * Selectors:: * Map Options::  File: am-utils.info, Node: Map Defaults, Next: Variable Expansion, Prev: Location Format, Up: Location Format Map Defaults ------------ A location beginning with a dash `-' is used to specify default values for subsequent locations. Any previously specified defaults in the location-list are discarded. The default string can be empty in which case no defaults apply. The location `-fs:=/mnt;opts:=ro' would set the local mount point to `/mnt' and cause mounts to be read-only by default. Defaults specified this way are appended to, and so override, any global map defaults given with `/defaults').  File: am-utils.info, Node: Variable Expansion, Next: Selectors, Prev: Map Defaults, Up: Location Format Variable Expansion ------------------ To allow generic location specifications Amd does variable expansion on each location and also on some of the option strings. Any option or selector appearing in the form `$"var"' is replaced by the current value of that option or selector. For example, if the value of `${key}' was `bin', `${autodir}' was `/a' and `${fs}' was `${autodir}/local/${key}' then after expansion `${fs}' would have the value `/a/local/bin'. Any environment variable can be accessed in a similar way. Two pathname operators are available when expanding a variable. If the variable name begins with `/' then only the last component of the pathname is substituted. For example, if `${path}' was `/foo/bar' then `${/path}' would be expanded to `bar'. Similarly, if the variable name ends with `/' then all but the last component of the pathname is substituted. In the previous example, `${path/}' would be expanded to `/foo'. Two domain name operators are also provided. If the variable name begins with `.' then only the domain part of the name is substituted. For example, if `${rhost}' was `swan.doc.ic.ac.uk' then `${.rhost}' would be expanded to `doc.ic.ac.uk'. Similarly, if the variable name ends with `.' then only the host component is substituted. In the previous example, `${rhost.}' would be expanded to `swan'. Variable expansion is a two phase process. Before a location is parsed, all references to selectors, eg `${path}', are expanded. The location is then parsed, selections are evaluated and option assignments recorded. If there were no selections or they all succeeded the location is used and the values of the following options are expanded in the order given: SUBLINK, RFS, FS, OPTS, REMOPTS, MOUNT and UNMOUNT. Note that expansion of option values is done after "all" assignments have been completed and not in a purely left to right order as is done by the shell. This generally has the desired effect but care must be taken if one of the options references another, in which case the ordering can become significant. There are two special cases concerning variable expansion: 1. before a map is consulted, any selectors in the name received from the kernel are expanded. For example, if the request from the kernel was for `${arch}.bin' and the machine architecture was `vax', the value given to `${key}' would be `vax.bin'. 2. the value of `${rhost}' is expanded and normalized before the other options are expanded. The normalization process strips any local sub-domain components. For example, if `${domain}' was `Berkeley.EDU' and `${rhost}' was initially `snow.Berkeley.EDU', after the normalization it would simply be `snow'. Hostname normalization is currently done in a _case-dependent_ manner.