Microsoft's fdisk program, run from the DOS command line, takes over the screen and has limited commands for creating primary, extended and logical partitions needed for MS Windows 95, 98, ME and so on.
Linux's fdisk program is scroll oriented. It is more flexible than most of the others, being able to create Microsoft extended partitions in primary slots 3 and 4, in addition to BSD and Solaris disklabels, and it can set the partition type to any of the 256 possible values you might need.
Solaris's fdisk program is very limited; it can only create primary partitions. The same program on Solaris/Sparc is provided, although somewhat useless and in fact dangerous.
fdisk programs of different kinds are also supplied with BSD and OS/2.
All of these programs are partly incompatible in subtle ways. It is not unusual for one program to ruin things as seen by another, or as seen by one or another operating system, and it's often hard to tell what's really going on and what's really ruined.The best time to play around with these is when your disk is new, or recently erased, and so damage is minimized.
Each file has a filename which is a string of characters. The files in a particular directory usually must have distinct names; that is, no two can have the same name. Kinds of files include Regular Files, Direcctories, Symlinks, and Special Device Files. Each kind of file has a different shaped icon: Regular Files have upright rectangles, Directories have wide rectangles, Symlinks have arrows, etc.
The rules of file names are different, depending on the filesystem that the file is on. Most filenames use Ascii characters, but for some languages, other character systems such as Unicode are needed.
Unix filesystems are usually case sensitive, that is, Alice, alice, ALICE, and alICE all are different filenames. More popular filesystems, as on MacOS and MS Windows, are case-insensitive, that is, alice and ALICE and other variations are considered to be the same name for the same file.
This means that if you ask for alice you might get ALICE, because that was the file that was there.Among case-insensitive filesystems, most newer ones retain case, whereas older ones flatten case. If you make a file deCamp on MacOS, for instance, the name will be remembered as just that, deCamp. If you do the same thing on early versions of MS DOS and MS Windows, however, the name will probably be remembered as DECAMP. Many Windows programs try to finesse over this problem by displaying such a file as decamp or Decamp.
The more modern kinds of filesystems allow filenames up to 255 characters long. Typically they store Unicode, either litterally as 16 bit characters, or as a UTF-8 byte stream. The trend is for Unicode, with language-specific case insensitivity and sorting order.
Older file systems have more strict rules. For instance, very old Unix filesystems only had room for 14 character names, and old MacOS filesystems only have room for 31 character names. Before Unix became popular, many systems restricted the kind of characters in filenames, such as RT-11, which allowed letters, digits and five punctuation marks.
FAT16 and FAT32 volumes, found on MS Windows systems, internally only have room for so-called 8.3 filenames, that is, up to 8 characters before the dot and up to 3 characters after the dot. There are other rules, such as having one and only one dot, even if you don't want it, folding case, etc. Starting with Windows 95, another layer of the file system allowed pretty much the usual 255 character names. In Linux, it is best to use this layer by mounting with the filesystem type vfat.
In some versions of Windows, the filename remapping caused problems. If a filename already fit the 8.3 rules, it would be remembered directly. If so, it would lose the case information - directory listings would be all caps or all lower case or whatever a program could guess. The file ViewName will be remembered case-flattened as VIEWNAME, whereas ViewNames will be remapped and remembered with case intact so it would behave normally. And some programs would still work with the internal filenames so ViewNames would be known by its internal name, something like VIEWNA~1. The system also has a strange limitation whereby it sometimes runs out of internal names, right after VIEWN~99.
Windows 2000 and XP tend to use a more modern filesystem called NTFS that is more comparable to a Unix filesystem with 255 characters, Unicode compatibility, etc.
Usually filesytem types go along with operating systems, but often different operating systems get drivers to access other filesystem types for intercompatibility. (As you might expect, Microsoft never does this, as it would validate competitors.) The drivers are needed for your currently running OS to mount the disk partition as one of its own. If you access a volume over a network, it appears to you as a network filesystem, not as the original filesystem. For instance, if a machine named tracer serves an EXT3 volume over NFS, it will appear to you as an NFS volume, not an EXT3 volume, and you'll need no such driver.
This is a table that should give you an idea of some of the most common filesystem types around; see man mount for more information on your system. Linux systems in particular are getting more and more different disk filesystem types for various purposes such as journaling or compatibility. NOTE: the information in this table is subject to change and the weaknesses of the author's memory.
filesystem type | Typically found | description | notes | Runs on Linux? | runs on Solaris? | runs on Mac OS X? | runs on MS Windows? |
---|---|---|---|---|---|---|---|
EXT2, EXT3 | Linux disks | Default Linux disk partition | intercompatible, upward and downward | very well | only with special drivers | no | no |
Solaris UFS | Solaris disks | default Solaris disk partition | don't mix up with BSD or OS X flavor | read-only, as ufs with special option | very well | no | no |
BSD UFS | BSD Disks | default BSD disk partition | don't mix up with Solaris flavor | read-only, as ufs with special option | no | very well | no |
HFS | old MacOS disks | default partition for MacOS version 8 and earlier | No larger than 2 gigabytes | if enabled | no | yes | no |
HFS Plus | modern MacOS disks | default Mac OS X partition | MacOS 8.1 and later | maybe | no | very well | no |
NFS | Unix networks | Network file serving system | files on other machines | as nfs | as nfs | as nfs | no |
AFP | Macintosh networks | Appletalk Filing Protocol | files on other machines | sometimes | rarely | very well | with special driver |
SMB | MS Windows networks | same as NetBIOS | files on other machines | Samba driver | Samba driver | Samba driver | native Netbios |
FAT16 | Wintel disks | Microsoft file system | No larger than 2 gigabytes | as vfat | as pcfs | as msdos | very well |
FAT32 | Wintel disks | Microsoft file system | as vfat | as pcfs | as msdos | very well | |
proc | Unix systems | Virtual file system that simply displays system process information | Each unix's version is slightly different | as proc | as proc | none | don't even think about it |
ISO 9660 | on most CDs | platform-independent CD filesystems | sometimes includes RockRidge or Joliet extensions | as iso9660 | as hsfs | as cd9660 | yes |
When talking about files and volumes, "to format" means to take a partition, and transform it into a volume. If partitioning is like constructing walls in a building, formatting is like installing shelves and furniture. The root directory of the volume is created during formatting. When done formatting, you are left with a volume with that root directory, possibly a few more directories and files, depending on your OS, and a lot of free space. Most important, though, you can start to create files and directories in it, whereas this was not possible right after partitioning.
Usually on Unix systems, you format with the mkfs command and its variants. See also man mkfs, Filesystem Type.
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