6.1 UNIX Fast File System Overview
6.1.1 File System Organization
6.1.2 File Names
6.1.3 Access Permissions
6.1.4 Time Stamps
6.1.5 Link Counts
6.1.6 Hard Links
6.1.7 Symbolic Links
6.2 Macintosh Hierarchical File System Overview
6.2.1 File System Organization
6.2.2 File Names
6.2.3 Access Permissions
6.2.4 Time Stamps
6.2.5 Aliases
6.3 CodeBuilder FFS
6.3.1 FFS Within a File
6.3.2 FFS Within a Partition
6.4 CodeBuilder UFS
6.4.1 File Names
6.4.1.1 Maximum Number of Characters
6.4.1.2 Case Sensitive File Names
6.4.1.3 Component Separators
6.4.1.4 Non-Printable Characters
6.4.2 Linked Files
6.4.2.1 Hard Links
6.4.3 Directory Link Counts
6.4.4 Locked Files
6.4.5 File Types
6.4.6 File Permissions
6.4.7 Time Stamps
6.5 CodeBuilder Root File System Layout
6.5.1 The root Directory Tree
6.5.2 The usr Directory Tree
6.5.3 The var Directory Tree
6.5.4 Major System Administration Files
Chapter 6.0 continues...
6.0 The CodeBuilder File Systems
In the traditional UNIX world, disks are devices that can be formatted
into file systems and mounted for access by UNIX applications. In the Macintosh
world, disks are called volumes. The Macintosh File Manager is the entity
responsible for formatting disks into volumes and controlling access to
the files on those volumes. CodeBuilder augments the MacOS HFS file system
with two UNIX file system implementations, a native fast file system (FFS)
and a UNIX file system that sits on top of the MacOS HFS (UFS).
The first, known as FFS, implements a traditional native UNIX fast file
system either within a single Macintosh file or in a SCSI disk partition.
There is no need to reformat or partition a volume to create a FFS within
a file, but that will be necessary for FFS on a partition. For an FFS within
a file, CodeBuilder continues to use the services of the Macintosh File
Manager, but only for basic I/O operations. For an FFS on a partition, CodeBuilder
interacts directly with the Macintosh SCSI Manager. Macintosh files may
be stored on an FFS, but they are not available for access by Macintosh
applications. A future extension of FFS will permit desktop mounting and
use by Macintosh applications.
The second file system, known as UFS, implements the UNIX file system on
top of the Macintosh hierarchical file system. CodeBuilder imposes UNIX
file system semantics on the Macintosh by mapping the UNIX file system requests
onto the appropriate Macintosh File Manager routines. UNIX files are stored
alongside Macintosh files, so there is no requirement to reformat/partition
existing HFS volumes.
6.1 UNIX Fast File System Overview
CodeBuilder's FFS is derived from the Berkeley BSD UNIX high-performance
file system. It is a simple and elegant file system that has its roots in
the original UNIX file system developed at Bell Labs. Detailed information
may be found in two supplementary documents: (1) A Fast File System
for UNIX, and (2) Fsck - The UNIX File System Check Program.
These are located in the Documentation folder under /CodeBuilder UNIX
Docs/Sys Admin's Docs (SMM)/fastfs.pdf or fsck.pdf.
6.1.1 File System Organization
UNIX disks are divided into one or more partitions. Each partition may contain
one file system, and a file system never spans multiple partitions. Critical
file system sizing parameters are stored in a super-block, which
is replicated to protect against catastrophic loss.
The file system stores files. Certain files are designated as directories
which contain pointers to other files, some of which may be other directory
files. Every file has an associated descriptor called an inode,
which contains ownership, permissions, time stamps, and pointers to assigned
data blocks.
A disk partition is divided into one or more areas called cylinder groups.
A small percentage of each cylinder group is taken for some bookkeeping
information, including a redundant copy of the super-block, inode slots,
a bitmap of available data blocks, and data block usage summary information.
A static number of inodes is allocated when the file system is created.
The default policy is to create one inode per 2048 bytes of space in the
cylinder group, which is expected to be far more than will be needed.
UNIX files are a single stream of bytes, with no operating system imposed
format. Text files use the ASCII 'LF' character ('\n') to denote an end-of-line.
Binary files often begin with a four byte code identifying the format of
the data that follows.
6.1.2 File Names
UNIX file and directory names are limited to 255 characters. MacOS file
names are limited to 31 characters. Names may not include the '/'
character because it is used in pathnames to separate directory and file
name components. An absolute pathname begins with a '/'; anything
else is relative to the current working directory. Name matching is case
sensitive. (MacOS file names are NOT case sensitive, however
Tenon's extension enables case sensitivity in Tenon's UFS file system.)
6.1.3 Access Permissions
UNIX file and directory access rights are divided into read, write, and
execute permissions. Read permission allows a user to examine the contents
of a file. Write permission allows a user to change or append data to a
file. Execute permission for binary files allows a user to execute the file
as a program, and for directories allows a user to search the directory.
Each file and directory is tagged with a user and group ID. Three levels
of permissions are specified, one for the owner of a file, a second for
the members of the designated group, and a third for "everyone else".
6.1.4 Time Stamps
UNIX saves three time stamps for each file: (1) the time the file's data
was modified, (2) the time the file's attributes were last modified, and
(3) the time the file was last accessed (i.e. the data was read).
6.1.5 Link Counts
Physical files are uniquely identified by their inode, but they may be identified
by multiple names. The link count is simply the number of references to
an inode.
6.1.6 Hard Links
The mapping of a file name in a directory to an inode is known as a hard
link. Hard links are not allowed to cross file system boundaries.
6.1.7 Symbolic Links
Symbolic links are special files whose content is the pathname of the intended
file or directory. The pathname may be absolute or relative, and may refer
to other file systems. Symbolic links may point to other symbolic links.
6.2 Macintosh Hierarchical File System Overview
The MacOS method of organizing files is known as the hierarchical file system
(HFS). Detailed information about the Macintosh file system and File Manager
may be found in the Files manual which is part of the Inside Macintosh documentation
series, published by Addison-Wesley.
6.2.1 File System Organization
Each Macintosh hard disk is formatted into a number of 512-byte addressable
units known as logical blocks. A volume is a consecutive
sequence of these blocks. Small disks are typically used whole as a single
volume, while large disks are often partitioned into two or more volumes.
A volume consists of overhead, file storage, and free space. The overhead
includes boot blocks, bitmap, master directory blocks, catalog and extents
files. The catalog file maintains the hierarchy of directories and files
on a volume, and the extents overflow file tracks assignment of allocation
blocks to files which cannot be stored in the catalog file. File storage
is assigned in units of allocation blocks, which are one or more consecutive
logical blocks. A volume has at most 65,536 allocation blocks.
This addressing constraint dictates the ratio of logical blocks to an allocation
block. Files are stored in directories (also known as folders), which are
themselves stored in directories. Each directory and file is assigned an
integer ID which uniquely identifies it on a given volume. Every volume
has a top directory known as the root directory, with a directory ID of
2. When a volume is mounted for use, the MacOS assigns a volume reference
number which remains valid as long as the volume is mounted. Macintosh files
are uniquely specified with a volume reference number, a parent directory
ID, and a file name.
A Macintosh file has two forks, a data fork and a resource fork. File data
resides in the data fork, while file resources are stored in the resource
fork. An application would typically have resources such as menus, dialog
boxes, icons, and even code segments. A document file could have resources
such as preference settings, window locations, fonts and icons. Files are
marked with a four byte creator and type, usually shown as alphanumeric
tags, such as APPL, TEXT, BINA. The creator identifies the application that
created the file, and the type generally indicates the file content. Text
files use the ASCII 'CR' character ('\r') to denote an end-of-line.
6.2.2 File Names
Macintosh file and folder names are limited to 31 characters. Names may
not include the ':' character because it is used in pathnames to
separate volume, directory, and the file name components. An absolute pathname
begins with a volume name. A pathname relative to the current working directory
begins with a ':'. The File Manager is not case sensitive when
matching file names, however, it does not ignore diacritical marks. (MacOS
file names are NOT case sensitive, however Tenon's extension
enables case sensitivity in Tenon's UFS file system.)
6.2.3 Access Permissions
Permissions for files on local volumes are based on the order and manner
in which programs open them. Files can be opened for reading, writing, or
exclusive read/write. Write access can be denied on an individual file basis
by setting its lock via Finder's Get Info dialog box. The File Manager also
prevents locked files in the Trash can from being deleted on an" Empty
Trash" request. Setting a volume to read-only (by hardware or software)
prevents any change to all files on that volume.
6.2.4 Time Stamps
The Macintosh File Manager saves three time stamps for each file: (1) the
time the file was created, (2) the time the file was last modified, and
(3) the time the file was last backed up (rarely used in the Macintosh world).
6.2.5 Aliases
An alias is a special kind of file that represents a file, folder, or volume.
6.3 CodeBuilder FFS
CodeBuilder's implementation of the UNIX Fast File System (FFS) allows it
to be stored within a Macintosh HFS file, or on a SCSI disk partition. Using
files allows existing volumes to be used as is, provided they have sufficient
space to meet file system sizing requirements. Using partitions provides
higher performance, but may require reformatting/partitioning disks.
6.3.1 FFS Within a File
Macintosh files which contain an FFS are treated as block devices by CodeBuilder.
They are set with creator 'MUMM' and type 'BLK '. These files are visible
to Finder and may be moved or copied to other folders or volumes. They may
also be dragged to the Trash can for removal. Be sure that this is intended
before requesting "Empty Trash"! These files should never be selected
for write access by other Macintosh applications. Even minor changes by
other Macintosh applications could render the fast file system file unusable
by CodeBuilder! See also section 6.9.1.1
Creating an FFS Within a File.
6.3.2 FFS Within a Partition
To establish an FFS in a partition, you must first create an A/UX partition
a disk with a Macintosh formatting application. This partition cannot be
mounted on the Macintosh desktop, so its content is not accessible by the
Finder or other Macintosh applications. See also section 6.9.1.2
Creating an FFS on a Partition.
6.4 CodeBuilder UFS
CodeBuilder's implementation of the local UNIX file system (UFS) uses the
Macintosh File Manager (HFS), enabling CodeBuilder's UNIX files to be stored
alongside Macintosh files. However, there are some constraints imposed by
the Macintosh File Manager that the astute user should be aware of when
porting other UNIX applications to CodeBuilder.
6.4.1 File Names
6.4.1.1 Maximum Number of Characters
The Macintosh File Manager allows a maximum of 31 characters in a file name;
hence, CodeBuilder UFS file names are limited to 31 characters.
6.4.1.2 Case Sensitive File Names
CodeBuilder supports case sensitive file names by appending a 4 byte integer
to the end of any case sensitive file name that collides with an existing
case insensitive name. HFS stores the length of the file name, hence the
names are unique within HFS. UNIX requests use a null terminated string
comparison for identifying files, hence the appropriate file is matched
as long as the first of the four appended bytes is NULL. CodeBuilder guarantees
that this is the case. For subsequent collisions, a new integer is used.
Since the HFS limit on file name length is 31 characters, this method of
resolving case sensitivity is limited to file names of length 27 characters
or less. Attempting to create a new file that collides with an existing
case insensitive file name of greater than 27 characters will fail.
6.4.1.3 Component Separators
The Macintosh File Manager uses the character ":" to separate
names into volume, folder, and file name components. Thus, Macintosh file
names cannot contain that character. UNIX uses the character "/"
for the same purpose. CodeBuilder automatically maps all occurrences of
":" (which is valid in UNIX file names) into "/" (which
is valid in Macintosh file names) before passing UNIX file names to the
Macintosh File Manager.
6.4.1.4 Non-Printable Characters
Macintosh file names often include unprintable characters (the trademark
symbol, for example). Although these characters are not invalid in UNIX
file names, they are impossible to type or display on a UNIX command line.
For this reason, non-printable ASCII characters in Macintosh file names
are translated according to the AppleSingle 7-bit ASCII naming conventionÝ.
Basically, non-printable characters are translated to a percent sign (%)
followed by a 2 digit hexadecimal representation of the character's value.
The following are some examples:
File
Name as Viewed by MacOS
| File Name as Viewed by CodeBuilder
|
FilenameTM
| Filename%aa
|
Filename®
| Filename%a8
|
Filename©
| Filename%a9
|
Ý: For more information on Apple Single, refer
to section 6.7.1 AppleSingle
Encapsulation.
6.4.2 Linked Files
In UNIX, linking allows several file names to be associated with the same
physical file. CodeBuilder properly supports UNIX hard and soft links via
the link(2) and symlink(2) system calls.
6.4.2.1 Hard Links
CodeBuilder provides a file system paradigm that permits copying or moving
either UNIX or Macintosh files with either UNIX or Macintosh tools with
equal results. However, the UNIX implementation of hard links prohibits
cross disk hard links. Using the Finder to copy CodeBuilder's hard links
from one volume to another will not work. Therefore, you cannot use the
Finder (or any other Macintosh tool) to copy or move CodeBuilder hard links
from one Macintosh volume to another. This restriction is similar to the
traditional UNIX restriction - no cross disk hard links.
CodeBuilder's implementation of hard links uses a hidden folder at the root
level of a volume, and uses the Macintosh HFS equivalent of inode
numbers to find targets of hard links in this folder. When the source of
a hard link is moved to another volume, the link will be unresolvable. Even
if the correct target of the link is copied from the source volume's hidden
folder, it will be assigned a new inode number and the source link
will still be unresolvable.
In general, unless an application requires specific semantics of hard links
that are not also supplied by soft links, soft links should be the preferred
method of linking UFS files.
6.4.3 Directory Link Counts
The stat() system call does not return the correct number of links
for a directory. The Macintosh File Manager does not keep a directory link
count for Macintosh folders, and CodeBuilder does not attempt to fabricate
a correct directory link count for UNIX directories on local Macintosh File
SystemsÝ.
Ý: CodeBuilder always returns a link count of
2 for UFS directories.
6.4.4 Locked Files
The Macintosh File System has the ability to lock individual files, effectively
making the file 'read only'. The UNIX file system has no notion of locking
for individual files, although it does support the locking of entire file
systems by mounting them as 'read only'. If a UNIX application attempts
to modify or remove a locked file, CodeBuilder will return the error EROFS.
Although this error implies that the entire file system is 'read only',
it may be only the individual file that is locked. In this case it is necessary
to unlock the file (use the Finder's Get Info entry in the File menu) before
CodeBuilder can modify or remove the file.
6.4.5 File Types
The Macintosh File Manager saves a file type and file creator as part of
the attributes for every file. CodeBuilder uses the identifier 'MUMM' for
UNIX files. In CodeBuilder documentation the term "UNIX file"
is used to refer to any file with a creator 'MUMM' and the term "Macintosh
file" is used to refer to all other files. Note that Macintosh applications
can see and access the UNIX files, since they are simply Macintosh files
with a creator 'MUMM'. Only CodeBuilder makes the distinction between UNIX
files and Macintosh files.
All CodeBuilder documents and files are owned by the application named CodeBuilder.
CodeBuilder uses file types for the different classes of files in UNIX.
Each file type has a unique icon, easing identification of UNIX files when
using the Macintosh Finder.
BINA - Binary Files
Binary files are streams of data. They may be UNIX executable files, text
files, database files, or others. No translation of the data is done on
binary files when accessed via CodeBuilder. This is the simplest, fastest,
and most common type of file. When CodeBuilder creates a new file, it always
creates files of type BINA.
TEXT - Text Files
Files containing only ASCII printable characters are referred to as "text"
files. The Macintosh and UNIX formats for text files have subtle differences.
Macintosh uses the character 'cr' (0xD) to terminate a line of text and
UNIX uses the character 'nl' (0xA). CodeBuilder files with a type 'TEXT'
are stored on the disk in the native Macintosh text file format (the line
terminator is 'cr').
When UNIX applications access type TEXT files, CodeBuilder automatically
translates the 'cr' character to 'nl', so the UNIX applications see these
files in the expected UNIX text file format. A result of this automatic
translation is that both Macintosh word processors and UNIX editors can
be used to edit 'MUMM'/'TEXT' files. Note that some Macintosh word processors
may inadvertently add resource forks to the UNIX text files, but these resource
forks will always be ignored by CodeBuilder. For more information on the
handling of text files in CodeBuilder, refer to the chapter "Text File
Manipulation".
LINK - Symbolic Links
This file type is used to identify UNIX symbolic links. The path to follow
for the symbolic link is stored in the data fork of the file.
CHR - Character Devices
This file type is used to identify UNIX character devices. UNIX assigns
two numbers to each device. The 'major' number describes the device type,
and the 'minor' number uniquely identifies the device. The major and minor
numbers for this device are packed in four bytes and are stored in the data
fork of the file.
BLK - Block Devices
This file type is used to identify UNIX block devices. The major and minor
numbers for this device are packed in four bytes and are stored in the data
fork of the file.
SOCK - Sockets
This file type is used to identify UNIX sockets. Sockets are communication
endpoints used for sending and receiving data.
FIFO - Pipes
This file type is used to identify named UNIX pipes. A pipe is a special
type of file that is created by UNIX processes in order to pass information
to other processes. Pipes enforce a first-in, first-out (FIFO) mechanism
on data.
HLNK - Hard Links
This file type is used to identify hard links. Hard linking allows several
file names to be associated with the same physical file.
SHLB - Shared Libraries
This file type is used to identify a shared library file. Many of the traditional
UNIX shared libraries (libc, libm, etc.) will have two
versions in CodeBuilder - one for the compile time Header Call definitions
and the other for the run time dynamic linking.
6.4.6 File Permissions
CodeBuilder stores the user id, group id, and mode bits in a reserved area
of the resource fork for each UNIX file. CodeBuilder can also set these
attributes for Macintosh filesÝ. Note that this protection
only applies to file access from CodeBuilder; it does not apply to the Finder
or other Macintosh applications.
CodeBuilder stores the protection attributes for a directory in a special
file within the folder. This file has the name '/' and is invisible
to the Finder. However, other Macintosh applications may see this file.
It should not be deleted or changed.
Figure 20. Example of File Permissions
Ý: The CodeBuilder application has resources which
allow the user to configure the default UNIX access privilege modes for
Macintosh files and folders; see the CodeBuilder Resources Appendix B.
6.4.7 Time Stamps
When CodeBuilder examines the time stamps of a Macintosh file, the file's
Macintosh creation time is used for the UNIX data modification time. The
file's Macintosh modification time is used for the UNIX attribute modification
times. The file's Macintosh last-backed-up time is used for the UNIX last-accessed-time.
When CodeBuilder modifies the time stamps of a Macintosh file, the file's
Macintosh creation time is set to the UNIX data modification time. The file's
Macintosh last-backed-up time is set to the UNIX last-accessed-time. The
file's Macintosh modification time is set to the UNIX attribute modification
time.
File Time Stamps
| Macintosh |
UNIX |
file created
| data last modified
|
file modified
| attributes last modified
|
file backed up
| data last accessed
|
Since most of the interaction between UNIX and Macintosh programs depends
on only the "modified" timestamp, the CodeBuilder interpretation
of the Macintosh timestamps provides Mac/UNIX interoperability. For example,
changing a source file with a UNIX tool (like vi) results in a
change to the file's "modified" timestamp. A Macintosh application
which subsequently accesses this file will notice the change in the modified
time, and will behave accordingly (e.g., a Macintosh development tool will
rebuild a project if the project depends on the modified source file). In
the reverse situation, a Macintosh editor will also change the file's "created"
and "modified" timestamp, which will be interpreted by UNIX programs
in the proper, "the-data-(or attribute)-has-been-modified" sense.
In some cases, the Macintosh editor may only change the UNIX attribute modification
time. In this case, it may be necessary to touch(8) the file from
within CodeBuilder to rebuild the project correctly.
6.5 CodeBuilder Root File System Layout
The CodeBuilder root file system is delivered as an FFS within a file. The
FFS file is named CodeBuilder_FFS, and resides in the same folder
as the CodeBuilder application. A companion folder named CodeBuilder_HFS
provides for UFS oriented storage.
At the top of the CodeBuilder File System hierarchy is the UNIX root directory,
also referred to as "/". The path "//"
is a special case in CodeBuilder that allows UNIX processes to refer to
files and folders outside of the CodeBuilder root. "//"
is interpreted to mean "the real root of the HFS volume that contains
the CodeBuilder file system hierarchy". The corresponding routines
in the CodeBuilder libraries (getwd(3)) have been modified to understand
a pathname that begins with "//".
6.5.1 The root Directory Tree
The root directory is represented by a "/" and
contains the following directories:
Name
| Description
|
CDROM
| Mount point for CodeBuilder CD-ROM.
|
base
| Base of source code and place for building binaries in CodeBuilder distribution.
|
bin
| Basic user utilities.
|
bootvol
| Symbolic link or mount point for the root of the MacOS boot volume.
|
dev
| Block, character and other special device files.
|
etc
| System configuration files and scripts..
|
hfs
| Symbolic link to CodeBuilder_HFS
|
lost+found
| Storage for files lost or corrupted by file system damage.
|
bin
| Basic user utilities.
|
mnt
| Temporary mount point.
|
sbin
| Basic system administration utilities.
|
tmp
| Directory for temporary files.
|
usr
| Contains majority of system utilities and files.
|
var
| Multi-purpose log, temporary, transient and spool files.
|
volume
| macmntd creates subdirectory mount points for removable volumes.
|
6.5.2 The usr Directory Tree
Name
| Description
|
X11
| Symbolic link to CodeBuilder X Window software.
|
X11R6
| CodeBuilder X11R6 software.
|
bin
| Binaries.
|
doc
| Miscellaneous documentation.
|
include
| include files.
|
info
| Documentation for GNU programs.
|
lib
| Libraries.
|
libexec
| Catchall for system daemons.
|
local
| Mount point for file system containing local applications and support
files.
|
macppc
| PowerPC-specific files go here.
|
man
| troff source for man pages.
|
sbin
| System administrator binary files.
|
share
| Text and database files readily shared among 4.4BSD systems.
|
src
| rpm support tree.
|
6.5.3 The var Directory Tree
Name
| Description
|
adm
| Administrative files.
|
at
| Timed command scheduling files.
|
backups
| Miscellaneous backup files.
|
cron
| cron data files.
|
db
| Database files.
|
games
| Miscellaneous game status and log files.
|
lib
| Dynamic, machine specific application support files.
|
lock
| Storage for emacs file locking.
|
log
| Miscellaneous system log files.
|
msgs
| System messages.
|
obj
| Object files.
|
preserve
| Temporary home of files preserved when editors fail.
|
run
| System information files, rebuilt after each reboot.
|
spool
| Miscellaneous printer spooling directories.
|
tmp
| Temporary files that are not discarded between system reboots.
|
6.5.4 Major System Administration Files
For details about these files, see on-line man pages.
Name
| Description
|
/etc/fstab
| Contains file system mount information [fstab(5)].
|
/etc/group
| Defines mapping of group numbers to names and authorized users [group(5)].
|
/etc/hosts
| Defines host names, aliases and IP address.
|
/etc/master.passwd
| Defines the set of users authorized to log in; provides mapping between
user id and name, default group, home directory, and shell [passwd(5)].
|
/etc/printcap
| Contains the list of available printers and the parameters used by the
line printer daemon [printcap(5)].
|
/etc/rc
| Contains the script of commands init(8) is to execute to establish
the desired environment [rc(8)] .
|
/etc/rc.conf
| Contains variables derived from information entered in the CodeBuilder
Control Panel for use by /etc/rc when starting CodeBuilder.
|
/etc/syslog.conf
| /usr/sbin/syslogd configuration file [syslog(8)].
|
/etc/ttys
| Specifies terminal support information for init(8) [ttys(5)].
|
/usr/share/misc/termcap
| Defines the capabilities for numerous terminal types [termcap(5)].
Being phased out by ncurses.
|
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