FreeBSD supports the Network File System (NFS), which allows a server to share directories and files with clients over a network. With NFS, users and programs can access files on remote systems as if they were stored locally.
- An automounter is any program or software facility which automatically mounts filesystems in response to access operations by user programs. These are system utilities (daemons under Unix) which, when notified of file and directory access….
- Introduction 1.1 Revision History. Versions below 1.5 - Authored by Don. Version 1.5 - Added the copyright and other minor details.Rahul Sundaram took over maintainance. Version 1.5.1 - Added details to the question about VFAT. Version 1.5.2 - Revision history and other minor corrections. Version 1.6 - Added a few questions and answers.
THE OUTSIDERS full text.pdf. Step:1 Install autofs package. Install the autofs package using below yum command if it is not installed. email protected # rpm -q autofs package autofs is not installed email protected # yum install autofs Step:2 Edit the Master map file (/etc/auto.master ) Add the following line.
NFS has many practical uses. Some of the more common uses include:
Data that would otherwise be duplicated on each client can be kept in a single location and accessed by clients on the network.
Several clients may need access to the
/usr/ports/distfiles
directory. Sharing that directory allows for quick access to the source files without having to download them to each client.On large networks, it is often more convenient to configure a central NFS server on which all user home directories are stored. Users can log into a client anywhere on the network and have access to their home directories.
Administration of NFS exports is simplified. For example, there is only one file system where security or backup policies must be set.
Removable media storage devices can be used by other machines on the network. This reduces the number of devices throughout the network and provides a centralized location to manage their security. It is often more convenient to install software on multiple machines from a centralized installation media.
NFS consists of a server and one or more clients. The client remotely accesses the data that is stored on the server machine. In order for this to function properly, a few processes have to be configured and running.
Versatil markdown 2 0 50 – markdowncommonmark hypernotebook editor. These daemons must be running on the server:
Daemon | Description |
---|---|
nfsd | The NFS daemon which services requests from NFS clients. |
mountd | The NFS mount daemon which carries out requests received from nfsd. |
rpcbind | This daemon allows NFS clients to discover which port the NFS server is using. |
Running nfsiod(8) on the client can improve performance, but is not required.
The file systems which the NFS server will share are specified in /etc/exports
. Each line in this file specifies a file system to be exported, which clients have access to that file system, and any access options. When adding entries to this file, each exported file system, its properties, and allowed hosts must occur on a single line. Icab 5 9 2. If no clients are listed in the entry, then any client on the network can mount that file system.
The following /etc/exports
entries demonstrate how to export file systems. The examples can be modified to match the file systems and client names on the reader's network. There are many options that can be used in this file, but only a few will be mentioned here. See exports(5) for the full list of options.
This example shows how to export /cdrom
to three hosts named alpha
, bravo
, and charlie
:
The -ro
flag makes the file system read-only, preventing clients from making any changes to the exported file system. This example assumes that the host names are either in DNS or in /etc/hosts
. Refer to hosts(5) if the network does not have a DNS server.
The next example exports /home
to three clients by IP address. This can be useful for networks without DNS or /etc/hosts
entries. The -alldirs
flag allows subdirectories to be mount points. In other words, it will not automatically mount the subdirectories, but will permit the client to mount the directories that are required as needed.
This next example exports /a
so that two clients from different domains may access that file system. The -maproot=root
allows root
on the remote system to write data on the exported file system as root
. If -maproot=root
is not specified, the client's root
user will be mapped to the server's nobody
account and will be subject to the access limitations defined for nobody
.
A client can only be specified once per file system. For example, if /usr
is a single file system, these entries would be invalid as both entries specify the same host:
The correct format for this situation is to use one entry:
The following is an example of a valid export list, where /usr
and /exports
are local file systems:
To enable the processes required by the NFS server at boot time, add these options to /etc/rc.conf
:
The server can be started now by running this command:
Whenever the NFS server is started, mountd also starts automatically. However, mountd only reads /etc/exports
when it is started. To make subsequent /etc/exports
edits take effect immediately, force mountd to reread it:
To enable NFS clients, set this option in each client's /etc/rc.conf
:
Then, run this command on each NFS client:
The client now has everything it needs to mount a remote file system. In these examples, the server's name is server
and the client's name is client
. To mount /home
on server
to the /mnt
mount point on client
:
The files and directories in /home
will now be available on client
, in the /mnt
directory.
To mount a remote file system each time the client boots, add it to /etc/fstab
:
Refer to fstab(5) for a description of all available options.
Some applications require file locking to operate correctly. To enable locking, add these lines to /etc/rc.conf
on both the client and server:
Then start the applications:
If locking is not required on the server, the NFS client can be configured to lock locally by including -L
when running mount. Refer to mount_nfs(8) for further details.
Note:
The autofs(5) automount facility is supported starting with FreeBSD 10.1-RELEASE. To use the automounter functionality in older versions of FreeBSD, use amd(8) instead. This chapter only describes the autofs(5) automounter.
The autofs(5) facility is a common name for several components that, together, allow for automatic mounting of remote and local filesystems whenever a file or directory within that file system is accessed. It consists of the kernel component, autofs(5), and several userspace applications: automount(8), automountd(8) and autounmountd(8). It serves as an alternative for amd(8) from previous FreeBSD releases. Amd is still provided for backward compatibility purposes, as the two use different map format; the one used by autofs is the same as with other SVR4 automounters, such as the ones in Solaris, MacOS X, and Linux.
The autofs(5) virtual filesystem is mounted on specified mountpoints by automount(8), usually invoked during boot.
Whenever a process attempts to access file within the autofs(5) mountpoint, the kernel will notify automountd(8) daemon and pause the triggering process. The automountd(8) daemon will handle kernel requests by finding the proper map and mounting the filesystem according to it, then signal the kernel to release blocked process. The autounmountd(8) daemon automatically unmounts automounted filesystems after some time, unless they are still being used.
The primary autofs configuration file is /etc/auto_master
. It assigns individual maps to top-level mounts. For an explanation of auto_master
and the map syntax, refer to auto_master(5).
There is a special automounter map mounted on /net
. When a file is accessed within this directory, autofs(5) looks up the corresponding remote mount and automatically mounts it. For instance, an attempt to access a file within /net/foobar/usr
would tell automountd(8) to mount the /usr
export from the host foobar
.
In this example, showmount -e
shows the exported file systems that can be mounted from the NFS server, foobar
:
The output from showmount
shows /usr
as an export. When changing directories to /host/foobar/usr
, automountd(8) intercepts the request and attempts to resolve the hostname foobar
. If successful, automountd(8) automatically mounts the source export.
Automounter 1 4 2 X 2
To enable autofs(5) at boot time, add this line to /etc/rc.conf
:
Then autofs(5) can be started by running:
The autofs(5) map format is the same as in other operating systems. Information about this format from other sources can be useful, like the Mac OS X document.
Consult the automount(8), automountd(8), autounmountd(8), and auto_master(5) manual pages for more information.
An automounter is any program or software facility which automatically mounts filesystems in response to access operations by user programs. These are system utilities (daemons under Unix) which, when notified of file and directory access attempts under selectively monitored subdirectory trees, dynamically and transparently make remote or local devices accessible.
The purpose of the automounter is to conserve local system resources and reduce the coupling between systems which are sharing filesystems with a number of servers. For example, a large to mid-sized organization might have hundreds of file servers and thousands of workstations or other nodes accessing files from any number of those servers at any time. Usually only a relatively small number of remote filesystems (exports) will be active on any given node at any given time. By deferring the mounting of such filesystem until they are actually needed, the need to track such mounts is reduced, increasing reliability, flexibility and performance.
Frequently one or more fileservers will be inaccessible (down for maintenance, on a remote and temporarily disconnected network, or accessed via a congested link). https://light-converse-keygen-crackstreamingdownload.peatix.com. It is also often necessary to relocate data from one file servers to another's to resolve capacity and load balancing issues. Macfamilytree 8 5 4 equals. Having data mount points automated makes it easier to reconfigure client systems in such events. In addition, some storage devices such as floppies, CD-ROMs and USB keys, should be able to be mounted only when the device is attached to the system.
These factors combine to pose challenges to older 'static' management methods of filesystem mount tables (the 'fstab' files on Unix systems). Automounter utilities address these challenges and allow sysadmins to consolidate and centralize the associations of mountpoints (directory names) to the remote filesystems (exports). When done properly, users can transparently access files and directories as if there were a single enterprise-wide filesystem to which all of their workstations and other nodes were attached.
It is also possible to use automounters to define multiple repositories for read-only data; client systems can automatically choose which repository to mount based on availability, file server load, or proximity on the network.
Home directories
Many establishments will have a number of file servers which host the home directories for various users. All workstations and other nodes internal to the organization (typically all those behind a common firewall separating them from the Internet) will be configured with automounter services so that any user logging into anynode implicitly triggers access to his or her own home directory which, consequently, is mounted at a common mountpoint, such as /home/'user'
. This allows users to access theirown files from anywhere in the enterprise, which is extremely useful in Unix environments where users will frequently be invoking commands on many remote systems via various job dispatching commands such as ssh, telnet, rsh or rlogin, and via the X11 and VNC protocols.
Shared data
Many computing tasks can be distributed across clusters or 'farms' of computing nodes. Commonly each of these nodes must operate on some portions of input data and contribute their results to some common pool of outputs (which typically requires some post processing concatenation or other aggregation). These input data and the storage space for the results are normally located on file servers (often on separate file servers for different projects or data sets).
Software shares and repositories
In many computing environments the user workstations and computing nodes do not host installations of the full range of software that users might want to access. Systems may be 'imaged' with a minimal or typical cross-section of the most commonly used software. Also some users in some environments might require specialized or occasional access to older versions of software (for instance developers may need to perform bug fixes and regression testing or some users may need access to archival data using out-dated tools).
Commonly, organizations will provide repositories or 'depots' of such software so that it can be installed as needed. These also may include full copies of the system images from which machines have their operating systems initially installed, or available for repair of any system files that may get corrupted during a machine's lifecycle.
Some software may require quite a bit of storage space or might be undergoing rapid (perhaps internal) development. In those cases the software may be installed on andconfigured to be run directly from the fileservers.
Dynamically variant automounts
In the simplest case a fileserver houses data and perhaps scripts which can be accessed by any system in an environment. However, there are certain types of files (executable binaries and shared libraries, in particular) which can only be used by specific types of hardware or specific versions of specific operating systems.
For situations like this, automounter utilities generally support some means of 'mapping' or 'interpolating' variable data into the mount arguments.
For example an organization with a mixture of Linux and Solaris systems might arrange to host their package repositories for each on a common file server using export names like depot:/export/linux
and depot:/export/solaris
respectively. Thereunder they might have directories for each of the OS versions that they support. Using the dynamic variation features in their automounter they might then configure all their systems so that any administrator on any machine in their enterprise could access available software updates under /software/updates
. A user on a Solaris system would find the Solaris compiled packages under /software
while a Red Hat or CentOS user would find RPMs for their particular OS version thereunder. Moreover a Solaris user on a SPARC workstation would have their /software/updates
mapped to an appropriate export for their system's architecture while a Solaris user on an x86 PC would transparently find their /software/updates
directory containing packages suited to their system. Some software (written in scripting languages such as Perl or Python) can be installed and/or run on any supported platform without porting, recompilation or re-packaging of any sort. Those might be located in a /software/common
export.
In some cases organizations may also use regional or location based variable/dynamic mappings --- so that users in one building or site are directed to closer file server which hosts replications of the resources that are hosted at other locations.
In all of these cases automounter utilities allow the users to access files and directories without regard for where they are actually located. Using an automounter the users and systems administrators can usually access files where they are 'supposed to be' and find that they appear to be there. https://jxlbb.over-blog.com/2020/12/dragonscales-4-master-chambers-download-free.html.
Software
The original automount software was developed by Tom Lyon at Sun Microsystems, and was introduced in SunOS 4.0 in 1988. [cite book
last = Callaghan
first = Brent
title = NFS Illustrated
origdate = 1999
url = http://books.google.com/books?id=y9GgPhjyOUwC
accessdate = 2007-12-23
edition =
series =
date =
year = 2000
month =
publisher = Addison-Wesley
isbn = 0201325705
pages = pp. 322-323 ] This implementation was eventually licensed to other commercial UNIX distributions. Under Solaris 2.0, first released in 1992, the automounter was implemented as a pseudofilesystem called 'autofs'.
In December 1989, 'amd', an automounter 'based in spirit' on the SunOS automount program, was released by Jan-Simon Pendry. [cite newsgroup
title = 'Amd' - An Automounter
author = Jan-Simon Pendry
date = 1989-12-01
newsgroup = comp.unix.wizards
url = http://groups.google.com/group/comp.protocols.nfs/msg/4951e03d27b7c7e2
accessdate = 2007-12-23] This is now also known as the Berkeley Automounter.
Linux automount utilities also use the name autofs.
Disadvantages and caveats
While automounter utilities (and remote filesystem in general) can provide centrally managed, consistent and largely transparent access to an organization's storage services they also can have their downsides.
Automounter 1 4 2 X 4
* Access to automounted directories can trigger delays while the automounter resolves the mapping and mounts the export into place.
* Timeouts can cause mounted directories to be unmounted (which can later results in the mount delays upon the next attempted access).
* The mapping of mountpoint to export arguments is often (usually) done via some directory service such as LDAP or NIS, which constitutes another dependency (potential point of failure)
* When some systems require frequent access to some resources while others only need occasional access, it can be difficult or impossible to use a consistent, enterprise-wide mixture of locally 'mirrored' (replicated) and automounted directories.
* When data is migrated from one file server (export) to another there can be an indeterminate number of systems which, for various reasons, still have an active mount on the old location ('stale NFS mounts'); these can cause issues which may even necessitate the reboot of otherwise perfectly stable hosts.
* Organizations can find that they've created a 'spaghetti' of mappings which can entail considerable management overhead and sometimes quite a bit of confusion among users and administrators.
* Users can become so accustomed to the transparency of automounted resources that they neglect to consider some of the differences in access semantics that may apply to networked filesystems as compared to locally mounted devices. In particular, programmers may be attempting to use 'locking' techniques which are safe and provide the desired atomicity guarantees on local filesystems, but which are documented as inherently vulnerable to race conditions when used on NFS.
Automounter 1 4 2 Player Games
References