FAT filesystem and Linux: Difference between revisions

Revision as of 01:06, 19 January 2015

Revision as of 17:04, 16 July 2015

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== Commonalities ==

As mentioned previously, all of the Linux filesystem drivers support all of the three File Allocation Table sizes, 12-bit, 16-bit, and 32-bit. Other common features that they all support are various Linux mounting options (specified with the <tt>-o</tt> option to the <tt>mount</tt> command):<ref name=Smith1 /><ref name=Smith2 />

;<tt>uid</tt> and <tt>gid</tt>:These two options tell the filesystem driver to set the (default, in the case of ''umsdos'') owner user ID and group ID to be a single, specified, value for all files in the volume. Both IDs are specified as numeric values (as to be found in the <tt>/etc/passwd</tt> file). So, for example, to specify to the ''vfat'' filesystem driver that all files and directories are to have owner ID 745 and group ID 15, the <tt>mount</tt> command would be invoked as <source lang=bash enclose=none>mount -t vfat -o uid=745,gid=15</source> .<ref name="Smith1" /><ref name="Smith2" /> Linux filesystem drivers do not at present incorporate support for [[FAT file password|file/directory password]]s on FAT12/FAT16/FAT32 volumes and multi-user [[FAT file access rights|world/group/owner access permissions for read/write/delete/execute rights]] on FAT12/FAT16 volumes as implemented in various operating systems of the Digital Research family, including [[DR-DOS]], [[PalmDOS]], [[Novell DOS]], [[OpenDOS]], [[FlexOS]], [[Concurrent DOS]], [[Multiuser DOS]], System Manager and [[REAL/32]].<!-- not sure if REAL/32 supports owner-IDs on FAT32. If it does it would require certain tweaks as the owner-ID entry is used for the high-word of the cluster number on FAT32 volumes now -->

;<tt>umask</tt>:This option sets the [[umask]] to apply globally to all files in the volume. For example, to specify to the ''vfat'' filesystem driver that no "group" or "other" access is to be allowed, the <tt>mount</tt> command would be invoked as <source lang=bash enclose=none>mount -t vfat -o umask=077</source> .<ref name="Smith1" /><ref name="Smith2" />

;<tt>conv</tt>:This option specifies ''file content conversion'' semantics. It is possible for the filesystem drivers to convert the newline conventions in files, between LF termination and CRLF termination, on the fly as files are read and written. By default this conversion is entirely disabled. The filesystem drivers can perform conversion for some files, attempting to auto-detect what files to convert based upon the extension portion of the filename, or globally for all files. These three conversion levels are specified as <tt>conv=b</tt> (for "binary"), <tt>conv=a</tt> (for "auto-detect"), and <tt>conv=t</tt> (for "text"), respectively. The latter two options carry an inherent risk of corrupting non-text file data. No conversion at all is the default.<ref name=Smith1 /><ref name=Smith2 />

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Most of the major Linux distributions, including RedHat, SuSE, and Debian, do not employ ''umsdos'' to permit installation of Linux on a FAT disc volume. A few distributions do, however.<ref name=Smith2>{{cite book|title=The multi-boot configuration handbook|series=Handbook Series|author=Roderick W. Smith|publisher=Que Publishing|year=2000|isbn=978-0-7897-2283-6|pages=256,341&ndash;342}}</ref> These include distributions such as Phat Linux, a distribution created by two schoolchildren which installs in <tt>C:\PHAT</tt> on DOS by unpacking a [[ZIP file]] and is booted by running a [[COMMAND.COM]] script named <tt>LINUX.BAT</tt>,<ref name=McCune /> and [[ZipSlack]]{{Citation needed|date=September 2009}}.

The UMSDOS project was started in 1992 by Jacques Gelinas and made available to the net in January 1994 as a patch. It was included in the standard distribution starting with kernel 1.1.36.{{Citation needed|date=September 2009}} UMSDOS was removed from the Linux 2.6.11 kernel for lack of maintenance.{{Citation needed|date=September 2009}} UVFAT, an extension of UMSDOS to use the Windows data structures for long filenames instead of its own, was discontinued before release.<ref>{{CitationCite neededweb|datetitle = UMSDOS filesystem: UVFAT support|url = http://linux.voyager.hr/umsdos/#uvfat|website = linux.voyager.hr|accessdate =September 20092015-07-16}}</ref> They should work in 2.4.x kernels.{{Citation needed|date=September 2009}}

Earlier Linux distributions which used UMSDOS are [[MuLinux]],<ref>[http://mulinux.narod.ru/en_index.html MuLinux Project]</ref> Monkey Linux <ref>[http://projectdevolve.tripod.com/text/descript.htm Monkey Linux Explained]</ref> and Winlinux 2000.<ref>[http://archive.is/20120707065033/http://articles.techrepublic.com.com/5100-10878_11-1044390.html The Linux/Windows combo: Use these resources to make it work]</ref>