filesystems File


Centralizes file system characteristics.


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.
  1. Name and value pairs must have some form of indentation. For example, a space or a tab.
  2. Blank spaces and comma characters are not allowed in the file system mount point. Commas are used only as delimiters for multiple values to a name.
  3. Do not place text before or after quotation marks. For example, dev=abc"/dev/fd0"def is not allowed and will result in undefined behavior.

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:
Automatically mounts a file system when the system is started. Unlike the true value, filesystems which are mounted with the automatic value are not mounted with the mount all command or unmounted with the unmount all command. By default, the '/', '/usr', '/var', and '/tmp' filesystems use the automatic value.
This file system is not mounted by default.
Mounts a file system as a read-only file system.
Mounts a file system as a removable file system. While open files are on it, a removable mounted file system works the same as a normally mounted file system. However, when no files are open, and no process has a current directory on the file system, all of the file system disk buffers in the file system are written to the medium, and the operating system cannot access the file system.
This file system is mounted by the mount all command. It is unmounted by the unmount 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.
options Comma-separated list of keywords that have meaning specific to a file system type. The options are passed to the file system at mount time.
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.


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
         vol        = "OS"
         mount      = false
         check      = false

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

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

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

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

         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.


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