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efs(4)									efs(4)

NAME    [Toc]    [Back]

     efs - layout of the Extent	File System

SYNOPSIS    [Toc]    [Back]

     #include <sys/param.h>
     #include <sys/fs/efs.h>

DESCRIPTION    [Toc]    [Back]

     An	Extent File System can reside on a regular disk	partition or on	a
     logical volume; see lv(1M).  The disk partition or	volume is divided into
     a certain number of 512-byte sectors, also	called basic blocks.  The
     current maximum size limit	of an Extent File System is 16777214 blocks,
     equivalent	to 8 gigabytes.

     The Extent	File System imposes a common format for	certain	vital
     information on its	underlying storage medium.  Basic block	0 is unused
     and is available to contain a bootstrap program or	other information.
     Basic block 1 is the superblock.  The format of an	Extent File System
     superblock	is:

	   * Structure of the superblock for the Extent	File System
	  struct efs {
		* This portion is read off the volume
	       long fs_size;	   /* size of filesystem, in sectors */
	       long fs_firstcg;	   /* bb offset	to first cg */
	       long fs_cgfsize;	   /* size of cylinder group in	bb's */
	       short fs_cgisize;   /* bb's in inodes per cylinder group	*/
	       short fs_sectors;   /* sectors per track	*/
	       short fs_heads;	   /* heads per	cylinder */
	       short fs_ncg;	   /* #	of groups in filesystem	*/
	       short fs_dirty;	   /* fs needs to be fsck'd */
	       time_t fs_time;	   /* last superblock update */
	       long fs_magic;	   /* magic number */
	       char fs_fname[6];   /* filesystem name */
	       char fs_fpack[6];   /* filesystem pack name */
	       long fs_bmsize;	   /* size of bitmap in	bytes */
	       long fs_tfree;	   /* total free data blocks */
	       long fs_tinode;	   /* total free inodes	*/
	       long fs_bmblock;	   /* bitmap location */
	       long fs_replsb;	   /* location of replicated superblock. */
	       char fs_spare[24];  /* space for	expansion */
	       long fs_checksum;   /* checksum of volume portion of fs */
		* The remainder	of this	structure, defined fully in
		* <sys/fs/efs_sb.h> is used by the operating system only.

									Page 1

efs(4)									efs(4)

     The struct	efs that is defined in <sys/fs/efs_sb.h> contains more fields.
     The extra fields are used internally by the operating system and are not
     discussed here.  If in doubt, consult the include file for	any recent
     changes to	both the section discussed here	and changes to relevant

     fs_size holds the size in basic blocks of the filesystem.	This variable
     is	filled in when the filesystem is first created with mkfs(1M).

     fs_firstcg	contains the basic block offset	to the first cylinder group.
     There are fs_ncg cylinder groups contained	in the filesystem.  Each
     cylinder group is composed	of fs_cgfsize basic blocks, of which
     fs_cgisize	basic blocks are used for inodes.

     fs_sectors	and fs_heads are used to specify the geometry of the
     underlying	disk containing	the filesystem.	 fs_heads is in	fact currently
     unused and	should not be relied upon.

     fs_dirty is a flag	that indicates if the filesystem needs to be checked
     by	the fsck(1M) program.

     The fs_time field contains	the time stamp of when the filesystem was last

     fs_name holds the name of the filesystem (where it	is mounted, more or
     less) and fs_fpack	contains which volume this filesystem is.  The
     fs_fpack field is singularly useless, but is provided for utility

     fs_magic is used to tag the superblock of the filesystem as an Extent
     File System.  There are two values	that are currently used	and a macro
     used to test for either one.

	  #define   EFS_MAGIC 0x072959
	  #define EFS_NEWMAGIC	   0x07295A
	  #define IS_EFS_MAGIC(x)  ((x == EFS_MAGIC) ||	(x == EFS_NEWMAGIC))

     The NEWMAGIC version was added in IRIX 3.3	when the superblock format
     changed slightly.	Filesystems created with that version of mkfs or later
     (or modified with mkfs -r or extended with	growfs)	get the	new magic
     number; otherwise the older magic number is retained, if present.

     The fs_bmsize field contains, in bytes, the size of the data block
     bitmap.  The data block bitmap is used for	data block allocation.	Each
     one in the	bitmap indicates a free	block.

     The fs_bmblock field contains the location	of the bitmap if it has	been
     moved from	its default location (basic block 2) because the filesystem
     has been constructed on a logical volume that has been extended (see

									Page 2

efs(4)									efs(4)

     fs_tfree and fs_tinode contain the	total free blocks and inodes,

     The fs_replsb field contains the location of a replicated superblock, if
     one exists.

     The fs_spare field	is reserved for	future use.

     Lastly, the fs_checksum variable holds a checksum of the above fields
     (not including itself).

     During the	mount(1M) of the filesystem, the fs_dirty and fs_checksum
     fields are	examined.  If fs_dirty is non-zero, or the fs_checksum
     variable does not match the systems computed checksum, the	filesystem
     must be cleaned with fsck before it can be	mounted.  If the filesystem is
     the root partition, this check is ignored,	as it is necessary to be able
     to	run fsck on a dirty root from a	dirty root.  For the format of an
     inode and its flags, see inode(4).

FILES    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

     fsck(1M), growfs(1M), mkfs(1M), inode(4).
filesystems(4)							filesystems(4)

NAME    [Toc]    [Back]

     filesystems: cdfs,	dos, fat, EFS, hfs, mac, iso9660, cd-rom, kfs, nfs,
     XFS, rockridge - IRIX filesystem types

DESCRIPTION    [Toc]    [Back]

     IRIX supports a number of different filesystems.  Some of these types are
     names that	can be used with the mount(1) command's	-t option.  Others are
     just common names and cannot be used with the mount command.  An example
     of	this is	the RockRidge type, which is a superset	of the iso9660
     filesystem	type.  Therefore RockRidge filesystems are mounted with	a
     command similar to	this:

	  mount	-t iso9660 -o ro /dev/rdsk/dks0d3vol /CDROM

     The following filesystem types are	supported:

     bds	 Not a file system type, an extension to NFS for bulk data
		 transfers.  The BDSpro	server is an optional product and must
		 be purchased separately.

     cdfs (CD-ROM)
		 Same as type iso9660 (see below); this	is the ABI compliant

     dos (fat)	 The filesystem	used by	many personal computers.  Types	1, 4,
		 and 6 are supported, included long names where	supported.
		 Type 5	(extended partitions) are supported only if mounted
		 with the partition # options.	IRIX support for dos
		 filesystems is	restricted to removable	disk devices such as
		 floppy	and floptical disks.  Filenames	on dos filesystems are
		 restricted to up to an	eight character	name followed by an
		 optional period and three character filename extension, for
		 most types.  Longer names are supported to a limited degree,
		 on the	types where the	native OS supports them.

     EFS	 The older extent-based	disk filesystem	used by	IRIX for disks
		 and also for IRIX software distribution CD-ROMs.  See efs(4)
		 for more details.

     fd		 A filesystem used to access process file descriptors.

     hfs (mac)	 The filesystem	used by	Macintosh computers.  IRIX support for
		 hfs filesystems is restricted to removable disk devices such
		 as floppy and floptical disks and to CD-ROMs.	A hfs file is
		 composed of three portions:  a	data fork, a resource fork,
		 and a desktop information entry.  The data fork appears in a
		 normal	directory.  The	resource fork in a special directory
		 (.HSResource) in the file's directory.	 The desktop
		 information for all files in a	directory is contained in the
		 special file .HSancillary.

									Page 1

filesystems(4)							filesystems(4)

     iso9660 (CD-ROM)
		 A CD-ROM filesystem type conforming to	ISO standard 9660.
		 iso9660 CD-ROMs are used when the contents of the CD-ROM is
		 intended to be	readable by a variety of operating systems.
		 You must install the optional subsystem eoe.sw.cdrom to be
		 able to mount and read	an iso9660 CD-ROM.  Also see RockRidge
		 below.	 Note that IRIX	software distribution CD-ROMs are not
		 iso9660 filesystems, they are efs filesystems.	 Music CDs are
		 not file structured and are not used as filesystems.  Music
		 CDs can be played using the CD-ROM drive using	cdman(1) or

     kfs	 A network filesystem used to access disks on located on
		 remote	computers using	AppleShare networking.	Generally,
		 AppleShare networking is used to access Macintosh computers.
		 Except	for the	disk location, kfs filesystems are identical
		 to hfs	filesystems.

     nfs	 A network filesystem used to access disks located on remote
		 computers.  Both NFS Version 2, and NFS Version 3 are
		 supported.  NFS is an optional	product	and must be purchased
		 separately.  The subsystem nfs.sw.nfs must be installed to
		 use NFS.

     proc	 A filesystem that provides access to the image	of each	active
		 process in the	system.

     hwgfs	 A filesystem that provides access to the system hardware

     RockRidge	 A filesystem layered on type of the iso9660 filesystem	type
		 (see above) that provides semantics closer to those of
		 standard UNIX filesystems.  In	particular, it supplies	file
		 permissions and allows	for directory hierarchies more than 8
		 levels	deep.

     XFS	 The next-generation 64-bit high performance journaling
		 filesystem used by IRIX for disks.  See xfs(4)	for more

     cachefs	 A caching filesystem for use with efs,	xfs, nfs, nfs3,
		 iso9660, hfs, dos, kfs, and cdfs.  See	cachefs(4) for

NOTE    [Toc]    [Back]

     The nfs and kfs filesystems are optional products.	 Support for iso9660
     filesystems is in the optional subsystem eoe.sw.cdrom.

     IRIX implements dos, hfs, iso9660,	and kfs	filesystems as user mode NFS
     daemons.  In some cases errors detected by	these daemons are reported as
     NFS errors.  Although NFS is a product option, support for	these
     filesystem	types is not dependent on the installation of NFS.

									Page 2

filesystems(4)							filesystems(4)

SEE ALSO    [Toc]    [Back]

     exportfs(1M), fpck(1M), fsck(1M), mediad(1M), mkfp(1M), mkfs(1M),
     mount(1M),	mount_kfs(1M), efs(4), fd(4), fstab(4),	hwgfs(4), proc(4),

									PPPPaaaaggggeeee 3333
[ Back ]
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