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Document:	ULTRIX-32 Guide to the Network File System
Order Number:	AA-ME99A-TE
Revision:	0
Pages:	60
Original Filename:

OCR Text

ULTRIX-32

Guide to the

Network File System

Order No. AA-ME99A-TE

ULTRIX-32 Operating System, Version 3.0

Digital

Equipment Corporation

The information in this document is subject to change without notice and should not be
construed as a commitment by Digital Equipment Corporation.
Digital Equipment Corporation
assumes no responsibility for any errors that may appear in this document.

The software described in this document is furnished under a license and may be used or
copied only in accordance with the terms of such license.
No responsibility is assumed for the use or reliability of software on equipment that is not
supplied by DIGITAL or its affiliated companies.

The following are trademarks of Digital Equipment Corporation:

DEC

Q-bus

VAX

DECnet

VAXstation

DECUS

ULTRIX

VMS

MASSBUS

ULTRIX-11

MicroVAX

ULTRIX-32

ULTRIX Worksystem Software

PDP

UNIBUS

dildlilt]a]1]

UNIX is a registered trademark of AT&T in the USA and other countries.

IBM is a registered trademark of International Business Machines Corporation.
MICOM is a registered trademark of Micom System, Inc.
This manual was written and produced by the ULTRIX Documentation Group in Nashua, New
Hampshire.

Contents

About This Guide
AUIEIICE ...eiieiiiiiie et
e e e oo

vii

Organization ........occoviiiiiiiiii

vii

...ccvvveiii
e
ee
iiiiiiieeeee

viii

CONVENTIONS 1ovviiiiiiiiiieiie et
e e tt
e e

viii

Related DoOCUMENTS

Introduction to the

Network File System

1.1 The Client and Server RelationshiD ........cccccoveevvevveeeeeeeeoeeoeeseeoeoon,

1-2

1.2 The NFS SEIVICE

1-3

..ecccviiiiiii
ettt ee e
eiriiii
ee ee
iii

1.3 The NFS LocKing ServiCe

........ccociviiiimoeeeeeeeieieeeeeeeeeeeeeeseeeesoeeeee
.

1-4

2 Setting Up the Network File System
2.1 Preparing to Set Up NFS

2-1

2.2 Setting Up NFS Automatically ........ccccceevveemieeeeeeeeeeeeeeoeeeoeeeooeos

2-3

2.3 Setting Up NFS Manually

........cccoooviiveeemeeeeeeeeeeeeeeeeeee oo,

2-4

2.3.1 Edit the /etc/exports File ......cccoooovemmooeemvmoieeeeoeeeeeeeeoeeeeo,
2.3.2 Edit the /etc/rc.local File .......ccccooveovoeeeoeeeeeeeeie oo

2-5

2.3.2.1 Make an Entry for the portmap Daemon ..........ccoooeun......
2.3.2.2 Make an Entry for the mountd Daemon ..........ooovvvevven.n.
2.3.2.3 Make Entries for the NFS Daemons .......cooovveeeemmmmmemsononn

2-5
2-5

2-6

2.3.2.4 Make an Entry for the NFS Locking Service

....................

2-6

2.3.3 Edit the /etc/fstab File .....cccoooiviiiiiiiiiiiiiiiiiiiiiineeeieee
e

2-7

2.3.4 Reboot the System

2-7

..ot

2.4 Modifying the NFS Environment

...........cccccovvvrivimiiiiiiiiiiiiiniieieeneeenenn,

2.4.1 Modifying the NFS Environment Automatically

2-8

....................

2-8

..........ccccocovunnnneen.

2-9

3.1 Mounting a Remote File System or Directory ........cceceovieiiorriiieennnns.

3-1

3.2 Programming With the NFS Locking Service ......ccccoovvverviiriirvrrunnnnn..

3-3

3.3 Locking Remote Files ..o

3-4

3.4 Recovering NFS I0CKS

....coiiiiiiiiiiiiiiiiiiiicc
ettt
e eeae e

3-5

3.5 Addressing System SeCUIILY .....cccocoiiiiviiiiiiiiiiiiiiiiiieeeeeeerieeeeeeeeerenenens

3-6

2.4.2 Modifying the NFS Environment Manually

3 Managing the Network File System

3.5.1 Superuser Access over the Network
3.5.2 Mailing to Superuser (root)

........cccccoovvviiiinnnivnnnnee,

Across NFS Systems

3.5.3 Port MONItOTING ...cooviviiiiiiiieee et

3-6
3-7

ee v

3-9

.........ccocociiviiiiirieiiiieeiieieeseeeeeenannn.

3-10

........cccceveeviiiiiiiiiiiiiiiemiiiicreeeneeenn.

3-11

3.5.4 Increasing System Security
3.6 Identifying System Differences

...

3.6.1 Some File Operations Fail .......ccccccooviiiiiviiiiiriiiiiiiiiiiiiiiiiiieeiiinans

3-12

3.6.2 System (Clock)

3-12

4 Troubleshooting the

Times Can Vary

Network File System

4.1 Network or Server Failures
4.2 Remote Mount Failures

...........cocccccicciiiiiiiiiiiiiiiinieiiiiiiieceenennn,

4-1

..........ccccocoviiiiiiiiiiiiiii
e,

4-3

4.3 Remote Mount Error MeSSages
4.4 Client Programs BloCK

.....ccoccoceeviiiiiiiiiiiiniieinieeennnnns

.......cccccvvvieiiiiuieemeieeeereeeeeeeieeeeeeeeeenenens

........coooviiiiiiiiiiiiiiiiiiie

4.4.1 The NFS Server IS DOWI

4-7

.oioeoeieieeeeiieiee
e ieeeeeeeeserna

4.7

4.4.2 The nfsd Daemon is Malfunctioning .........cccccceveeeeevvvcvvvvnnanrnn..
4.4.3 Two Or More Processes Are Deadlocked ......c.cc.cccovvvvvvevinnnn...

4.5 System Hangs Part Way Through Boot
4.6 Slow Remote File ACCESS

4-8
4-8

.......ccccceeevveivvvvveeiiieeesennenn,

4-8

..cccccovreiiiiiiiiiiiiiiieiii
et
eee e e eieeie
seerea e

4-9

4.7 NFS Console Error MeSSAges

.......cccccccovviiviiiviiniieeeiieeeeeseieeesssssinneens

4-10

Index

Figures

1-1:

Host Systems Running NFS

...
eeeens

1-2

3-1:

Relationship of Client and Server with the NFS Locking
SEIVICE tiiiiiiiiiiieerie sttt ettt
e e e eeteeeeaeee e s e e eenans

3-5

About This Guide

The objective of this guide is to provide introductory, setup, and
troubleshooting information for the Network File System (NFS).
This
guide will also assist you in developing NFS management procedures.
It
presents guidelines from which you can develop specific procedures for your
site.

Audience
This guide is meant for the person responsible for maintaining networks on
an ULTRIX operating system.
This person is usually the system manager,

but could be a network manager or the system manager who is also a user
of a MicroVAX processor running the ULTRIX operating system.
This
guide assumes that the reader is familiar with the ULTRIX system

commands, the system configuration, the naming conventions, and an editor

such as vi or ed.
It also assumes the reader knows the names and
addresses of the other systems on the network.

Organization
This guide consists of four chapters and an index.

The chapters are:

Chapter 1: Introduction
This chapter introduces the Network File System (NFS) and describes
It provides the background information needed
before you can set up and run NFS on your system.
Basic NFS
basic NFS concepts.

concepts are described.

Chapter 2: Setting Up the Network File System
This chapter describes how to set up NFS automatically on your
system, using the nfssetup command.

NFS manually.

want to understand how NFS

NFS.

It also describes how to set up

The manual description is included for those who
operates and which files are affected by

Chapter 3: Managing the Network File System
This chapter describes how to mount and unmount remote file
systems over NFS and provides general considerations, such as the
implications of mounting a remote file system on a local mount point.

This chapter also discusses the optimum NFS configurations, such as
how many NFS daemons should be running.
This chapter addresses system security with NFS and provides
information on how to improve security.
Finally, this chapter addresses system behaviors that you may notice
while running NFS on your system that were not apparent before
NFS was set up.
Chapter 4: Troubleshooting NFS

This chapter describes the basic approach to solving NFS-related
It discusses various system problems you may

system problems.

encounter and describes how to solve them.
In addition, this chapter
lists the NFS error messages and suggested user actions.

Related Documents
You should have available the related hardware documentation for your
system.
You also should have the other documents in the ULTRIX
documentation set, including the ULTRIX Reference Pages.

Conventions
The following conventions are used in this guide:

special

In text, each mention of a specific command, option,
partition, pathname, directory, or file is presented in this
type.

command(x)

In text, cross-references to the command documentation
include the section number in the reference manual where

the commands are documented.
For example:
See the
cat(1l) command.
This indicates that you can find the
material on the cat command in Section 1 of the ULTRIX
Reference Pages.

literal

In syntax descriptions, this type indicates terms that are
constant and must be typed just as they are presented.

italics

In syntax descriptions, this type indicates terms that are

variable.
[ ]

In syntax descriptions, square brackets indicate terms that
are optional.

In syntax descriptions, a horizontal ellipsis indicates that
the preceding item can be repeated one or more times.

function

In function definitions, the function itself is shown in this
type. The function arguments are shown in italics.

UPPERCASE

The ULTRIX system differentiates between lowercase and
Enter uppercase characters only
where specifically indicated by an example or a syntax line.
uppercase characters.

example

In examples, computer output text is printed in this type.

example

In examples, user input is printed in this bold type.

This is the default user prompt in multiuser mode.

This is the default superuser prompt.

>>>

This is the console subsystem prompt.
In examples, a vertical ellipsis indicates that not all of the
lines of the example are shown.

KEYNAME

In examples, a word or abbreviation in angle brackets
indicates that you must press the named key on the
terminal keyboard.

CTRL/x

In examples, symbols like this indicate that you must hold
down the CTRL key while you type the key that follows

the slash.

Use of this combination of keys may appear on

your terminal screen as the letter preceded by the
circumflex character.
In some instances, it may not appear
at all.

Introduction to the Network File System 1

This chapter provides an overview of the Network File System (NFS),
discusses how to maintain NFS, and describes the related files.
NFS is a facility for sharing files in a heterogeneous environment of
processors, operating systems, and networks.

Sharing is accomplished by

mounting a remote file system or directory and then reading or writing the

files as though they were local.

This sharing removes the need to copy

files across the network from one system to another and makes it easier

to access remote files.

It also reduces the risk of having copies of the

same file on different systems become out-of-date, because the sole copy
can be kept on a single host system.

Client systems request resources provided by other systems, called servers.
A client is any host system or process generated by a piece of software,
such as NFS or Yellow Pages (YP), that uses services from a server.

is discussed in the Guide to the Yellow Pages Service.
A server is any host system or process that provides a network service
such as NFS or YP.

A single host can provide more than one service.

Servers are passive; they wait for clients to call them.

Servers never call

the clients.
There is not necessarily a one-to-one correspondence between servers,
clients, and systems.
client.

A system that acts as a server can also act as a

For example, NFS allows clients to mount remote file systems and

directories and to access the files within the remote directories locally,
provided a server has exported the directory.

A server that exports file

systems and directories can also mount remote file systems and directories
exported by other systems, thus becoming a client.
To export a file system or directory is to make it available for NFS
clients to mount remotely onto their local systems.

The /etc/exports file

defines the NFS file systems and directories that can be exported.
A server makes specified file systems and directories available which clients
can then mount as remote file systems and directories.

In this way, users

can access remote files as if they were on the local system.
The client always initiates the remote mount.

The server completes the

binding subject to access control rules specific to NFS.

Because most

network administration problems occur at bind time, you should know how
a client binds to a server and what access control policy each server uses.

If you are running NFS, you may elect to use the NFS locking service.
This service supports file and file region advisory locking on local and
remote systems.
This is important when several users or processes access

the same file simultaneously.

The topics discussed in this chapter are:
o

The client and server relationship

The NFS service

The NFS locking service

1.1

The Client and Server Relationship

An NFS client selects a specific server from which to mount a given file
system or directory.
It can choose to mount file systems and directories

from a number of servers.

Figure 1-1 shows the relationship between several host systems connected
by an Ethernet cable to the same network.
There is one NFS client and
four NFS servers on the network shown.
Note that System A is both an
NFS client and server.

System A

Client/
Server

cinernet

Server

System C

System D

System

I
ZK-0011U-GE

Figure

1-1: Host Systems Running NFS

1.2

The

NFS Service

This section briefly describes the service that NFS provides.
It describes
the /etc/fstab and /etc/exports files and identifies the four programs that

implement NFS.

NFS enables users to share files over the network.
unmount file systems and directories from an NFS

A client can mount or
server.

The client

always initiates the binding to a server’s file system or directory by
using
the mount command.
Once a remote file system or directory is mounted,
it is treated as a file system by the client.
Typically, a client mounts one

or more remote file systems and directories at startup
time, if lines

to the following are in the /etc/fstab file.
lines when the system comes up:

similar

The mount command reads these

/usr2@titan:/usr2:rw:O:O:nfs:hard,bg:
/usr/man@venus:/usr/man:rw:O:O:nfs:hard,bg:

See fstab(5)
format.

in the ULTRIX Reference Pages for a description of the file

NFS servers control who can mount their resources by limiting
named file
systems and directories to a specific set of clients with an
entry in the

letc/exports file.

Note that the /etc/exports file allows you to limit access
to NFS clients, but not to individual remote users.

Each NFS request is checked to make sure the file system or
directory
being accessed is currently exported.
If it is not, the operation fails.
The

mountd daemon marks exported file systems and directories
based upon the
information in the /etc/exports file.
If this file is modified, the next time
the mountd daemon processes a request, it updates the export
state on the
server.

The /etc/exports file defines which file systems and directories can be

exported to which hosts on the network.

There can be only one entry in
the /etc/exports file per file system or directory being exported.
The
following example shows entries for the letclexports file:
/usr/staff/doe
/usr/staff

-o

green
pink

/usr/local
/usr2

pink

green

black

export