Files Reference

filesystems File

Purpose

Centralizes file system characteristics.

Description

A file system is a complete directory structure, including a root ( / ) directory and any directories and files beneath it. A file system is confined to a logical volume. All of the information about the file system is centralized in the /etc/filesystems file. Most of the file system maintenance commands take their defaults from this file. The file is organized into stanza names that are file system names and contents that are attribute-value pairs specifying characteristics of the file system.

The filesystems file serves two purposes:

It documents the layout characteristics of the file systems.
It frees the person who sets up the file system from having to enter and remember items such as the device where the file system resides, because this information is defined in the file.

File System Attributes

Each stanza names the directory where the file system is normally mounted. The file system attributes specify all the parameters of the file system. The attributes currently used are:

Attribute	Description
account	Used by the dodisk command to determine the file systems to be processed by the accounting system. This value can be either the True or False value.
boot	Used by the mkfs command to initialize the boot block of a new file system. This specifies the name of the load module to be placed into the first block of the file system.
check	Used by the fsck command to determine the default file systems to be checked. The True value enables checking while the False value disables checking. If a number, rather than the True value is specified, the file system is checked in the specified pass of checking. Multiple pass checking, described in the fsck command, permits file systems on different drives to be checked in parallel.
dev	Identifies, for local mounts, either the block special file where the file system resides or the file or directory to be mounted. System management utilities use this attribute to map file system names to the corresponding device names. For remote mounts, it identifies the file or directory to be mounted.
free	This value can be either `True` or `False`. Obsolete and ignored.
mount	Used by the mount command to determine whether this file system should be mounted by default. The possible values of the mount attribute are: automatic Automatically mounts a file system when the system is started. For example, in the sample file, the root file system line is the mount=automatic attribute. This means that the root file system mounts automatically when the system is started. The True value is not used so that mount all does not try to mount it, and umount all doesn't try to unmount it. Also, it is not the False value because certain utilities, such as the ncheck command, normally avoid file systems with a value of the mount=False attribute. False This file system is not mounted by default. readonly This file system is mounted as read-only. True This file system is mounted by the mount all command. It is unmounted by the umount all command. The mount all command is issued during system initialization to mount automatically all such file systems. nodename Used by the mount command to determine which node contains the remote file system. If this attribute is not present, the mount is a local mount. The value of the nodename attribute should be a valid node nickname. This value can be overridden with the mount -n command.
size	Used by the mkfs command for reference and to build the file system. The value is the number of 512-byte blocks in the file system.
type	Used to group related mounts. When the mount -t String command is issued, all of the currently unmounted file systems with a type attribute equal to the String parameter are mounted.
vfs	Specifies the type of mount. For example, vfs=nfs specifies the virtual file system being mounted is an NFS file system.
vol	Used by the mkfs command when initializing the label on a new file system. The value is a volume or pack label using a maximum of 6 characters.
log	The LVName must be the full path name of the filesystem logging logical volume name to which log data is written as this file system is modified. This is only valid for journaled file systems.

Examples

The following is an example of a typical /etc/filesystems file:

Note

Modifying this file can cause several effects to file systems.

*
* File system information
*
default:
         vol        = "OS"
         mount      = false
         check      = false

/:
         dev        = /dev/hd4
         vol        = "root"
         mount      = automatic
         check      = true
         log        = /dev/hd8

/home:
         dev        = /dev/hd1
         vol        = "u"
         mount      = true
         check      = true
         log        = /dev/hd8

/home/joe/1:
         dev        = /home/joe/1
         nodename   = vance
         vfs        = nfs

/usr:
         dev        = /dev/hd2
         vol        = "usr"
         mount      = true
         check      = true
         log        = /dev/hd8

/tmp:
         dev        = /dev/hd3
         vol        = "tmp"
         mount      = true
         check      = true
         log        = dev/hd8

Note

The asterisk (*) is the comment character used in the /etc/filesystems file.

Files

/etc/filesystems	Lists the known file systems and defines their characteristics.
/etc/vfs	Contains descriptions of virtual file system types.

Related Information

The backup command, df command, dodisk command, fsck command, mkfs command, mount command, restore command, umount command.

The filesys.h file.

Files Overview.

Directory Overview and Logical Volume Storage Overview in AIX 5L Version 5.2 System Management Concepts: Operating System and Devices.