CHAPTER 4
Administering File Systems

New File System Features in Solaris 2.6

The Default SunOS 5.x File System

The Virtual File System Table (/etc/vfstab)

File System Administrative Commands

Making File Systems Available

Checking the Data Consistency of a File System (fsck)

Backing Up and Restoring File Systems

Creating Cache File Systems

A FILE SYSTEM IS A STRUCTURE OF DIRECTORIES USED TO LOCATE AND STORE files. The term file system is used in several different ways:

•  To describe the entire file tree from the root directory downward

•  To describe a particular type of file system: disk-based, network-based, or pseudo

•  To describe the data structure of a disk slice or other media storage device

•  To describe a portion of a file tree structure that is attached to a mount point on the main file tree so that that portion is accessible

Usually, you can tell from context which meaning is intended.

The SunOS 5.x system software uses the virtual file system (VFS) architecture, which provides a standard interface for different file system types. The kernel handles basic operations — such as reading, writing, and listing files — without requiring the user or program to know about the underlying file system type.

The file system administrative commands provide a common interface that allows you to maintain file systems of different types. These commands have two components: a generic component and a component specific to each type of file system. The generic commands apply to most types of file systems; the specific commands apply to only one type of file system.

Administering the SunOS 5.x file system is one of your most important system administration tasks. The file system story is a complex one, and understanding it can help you more effectively administer file systems. This chapter describes:

•  The types of file systems

•  The default SunOS 5.x file system

•  The virtual file system table (/etc /vfstab)

•  The file system administrative commands

•  Making local and remote files available to users

•  Backing up and restoring file systems

New File System Features in Solaris 2.6

The Solaris 2.6 release provides some new file system features. Each of these new features is introduced in the following sections.

Large Files

The mount command provides a new option, -largefiles, that is the default mount option for the Solaris 2.6 environment. This option enables you to create file systems that can contain files larger than 2 Gbytes. When files are mounted with the -largefiles option, a file system may contain files larger than 2 Gbytes, but it is not required. See “Making File Systems Available” for more information.

NFS Client Failover

With the NFS client failover feature, you can specify additional hosts from which to mount a file system in case the first host cannot be reached. You can either set this feature in the /etc/vfstab file or issue your list of hosts from the command line.

WebNFS

The WebNFS feature, sometimes called Public NFS, provides two additional options to the mount command:

•  The -index filename option automatically loads a file matching filename if it is found in a directory referenced by an NFS URL.

•  The -public option resets the public file handle to the current directory. This option enables you to access files through an NFS URL even if the file system cannot be mounted in the usual way.

See “Making File Systems Available” for more information.

Types of File Systems

The SunOS 5.x system software supports three types of file systems:

•  Disk-based

•  Network-based

•  Virtual (previously called pseudo)

Disk-Based File Systems

Disk-based file systems are stored on physical media such as hard disks, CD-ROMs, and diskettes. Disk-based file systems can be written in different formats. The available formats are:

•  UFS UNIX file system (based on the BSD Fat Fast File system that was provided in the 4.3 Tahoe release). The default disk-based file system in SunOS 5.x system software is UFS.

•  S5FS x86 UNIX file system (based on the BSD Fat Fast File system that was provided in the 4.3 Tahoe release). The default disk-based file system in SunOS 5.x x86 system software is S5FS.

•  HSFS High Sierra and ISO 9660 file system. High Sierra is the first CD-ROM file system; ISO 9660 is the official standard. The HSFS file system is used on CD-ROM, and is a read-only file system. The SunOS 5.x hsfs supports Rock Ridge extensions, which provide all UFS file system semantics and file types except for writability and hard links.

•  PCFS PC file system, which allows read /write access to data and programs on DOS-formatted floppy disks written for DOS-based personal computers.

The System V (S5) file system traditionally provided with System V releases is not included in the SunOS 5.x system software because of significant limitations, such as a maximum of 64,000 files in a file system, a restriction of 14 characters for file names, and lack of a quota facility.

Each type of disk-based file system is customarily associated with a particular media device:

•  UFS and S5FS with hard disk and any other media (tape, CD-ROM, diskette)

•  HSFS with CD-ROM

•  PCFS with diskette

These associations are not, however, restrictive. For example, CD-ROMs and diskettes can have UFS file systems installed on them.

Network-Based File Systems

Network-based file systems are file systems that are accessed over the network. Typically, network-based file systems are file systems that reside on one system and are accessed by other systems across the network. The available network-based file systems are:

•  NFS — network or distributed file system

•  RFS — remote file sharing

The default SunOS 5.x distributed file system is NFS. You administer distributed file systems by sharing them (exporting them from a server) and mounting them on individual systems. See “Making File Systems Available” later in the chapter for more information.