Partition - Revision history

Pbug at 18:14, 1 November 2005

2005-11-01T18:14:06Z

← Older revision		Revision as of 11:14, 1 November 2005
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	In some Operating Systems (<i>e.g.</i> [[Linux]] and [[Windows]]) to put a filesystem directly on one of the slices. Conceptually, this looks like:		In some Operating Systems (<i>e.g.</i> [[Linux]] and [[Windows]]) to put a filesystem directly on one of the slices. Conceptually, this looks like:


			----
	[[image:Partition1.png]]		[[image:Partition1.png]]
			----

	Not so with most other UNIX-like Operating systems (including all of the BSD variants and Solaris X86) which will put a partition table '''inside''' the slice. Individual partitions will hold filesystems such as / ([[root]]), /usr, /var, /tmp, /usr/home and so on. In [[OpenBSD]] up to 16 partitions are allowed. The program [[disklabel]] (in [[FreeBSD]] it's called bsdlabel) manages the partitions:		Not so with most other UNIX-like Operating systems (including all of the BSD variants and Solaris X86) which will put a partition table '''inside''' the slice. Individual partitions will hold filesystems such as / ([[root]]), /usr, /var, /tmp, /usr/home and so on. In [[OpenBSD]] up to 16 partitions are allowed. The program [[disklabel]] (in [[FreeBSD]] it's called bsdlabel) manages the partitions:
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	The 3rd partition or 'c' always represents the entire slice (In [[OpenBSD]]'s case the entire disk--this is possible since OpenBSD uses an absolute offset for managing it's partitions, and can adderss the entire disk directly). Generally, slice 'c' should not be used directly for a filesystem. Visually, this looks similar to:		The 3rd partition or 'c' always represents the entire slice (In [[OpenBSD]]'s case the entire disk--this is possible since OpenBSD uses an absolute offset for managing it's partitions, and can adderss the entire disk directly). Generally, slice 'c' should not be used directly for a filesystem. Visually, this looks similar to:

			----
	[[image:Partition2.png]]		[[image:Partition2.png]]
			----

	$ df		$ df

Hawson at 18:05, 1 November 2005

2005-11-01T18:05:35Z

← Older revision		Revision as of 11:05, 1 November 2005
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	Here is a review of disk partitions.		Here is a review of disk partitions.

	First, you have a disk. Within this disk, there is a slice table (also called "partition table" under Linux and Windows to further confuse things). The slice table is modified/managed with the [[fdisk]] program. In the slice table, you can have 4 primary slices ~~or 3~~ primary ~~slices and~~ up to 23 logical slices. In the ~~case~~ of logical ~~slices~~, ~~they~~ are ~~all contained within~~ a ~~single primary~~ slice. A slice is identified by an 8 bit number indicating what sort of slice this is here are a few common ones:		First, you have a disk. Within this disk, there is a slice table (also called "partition table" under Linux and Windows to further confuse things). The slice table is modified/managed with the [[fdisk]] program. In the slice table, you can have up to 4 primary slices.

			One of four primary paritions can act as a "container" for up to 23 logical slices. Logical partitions are ''usually'' located within primary partition #4, but this is merely convention, and ''not'' a requirement. The numbering for logical slices '''always''' starts at "5", regardless of the number of primary partitions. The aggregate size of logical paritions cannot exceed the size of the primary partition in which they reside; however, it is permissable to have unused space.

			Slices and partitions are allowed to overlap, but this is typcially a very bad idea. That said, below for information on slice "c" or "2" below, which typically refers to the "whole disk."



			A slice is identified by an 8 bit number indicating what sort of slice this is here are a few common ones:

	*0x04 DOS FAT-16		*0x04 DOS FAT-16
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	i: 65802177 63 unknown # Cyl 0*- 65279		i: 65802177 63 unknown # Cyl 0*- 65279

	Note: These partitions can then be [[newfs]]'ed and [[mount]]ed from the device which is represented by the name of the driver, the disk number (starting from 0) and the partition number (a through p). The 3rd partition or 'c' always represents the entire slice (In [[OpenBSD]]'s case the entire disk). Generally, slice 'c' should not be used directly for a filesystem. Visually, this looks similar to:		Note: These partitions can then be [[newfs]]'ed and [[mount]]ed from the device which is represented by the name of the driver, the disk number (starting from 0) and the partition number (a through p).

			The 3rd partition or 'c' always represents the entire slice (In [[OpenBSD]]'s case the entire disk--this is possible since OpenBSD uses an absolute offset for managing it's partitions, and can adderss the entire disk directly). Generally, slice 'c' should not be used directly for a filesystem. Visually, this looks similar to:

	[[image:Partition2.png]]		[[image:Partition2.png]]

Hawson: Grammatical corrections and images.

2005-11-01T17:05:23Z

Grammatical corrections and images.

← Older revision		Revision as of 10:05, 1 November 2005
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	~~To eliminate confusion here~~ is a review of ~~what a partition is~~. First you have a disk, this disk ~~has~~ a slice table (also called partition table ~~for confusings sake~~). The slice table is modified/managed with the [[fdisk]] program. In the slice table you can have 4 primary slices or 3 primary slices and up to 23 logical slices. A slice is identified by an 8 bit number indicating what sort of slice this is here are a few common ones:		Here is a review of disk partitions.

			First, you have a disk. Within this disk, there is a slice table (also called "partition table" under Linux and Windows to further confuse things). The slice table is modified/managed with the [[fdisk]] program. In the slice table, you can have 4 primary slices or 3 primary slices and up to 23 logical slices. In the case of logical slices, they are all contained within a single primary slice. A slice is identified by an 8 bit number indicating what sort of slice this is here are a few common ones:

	*0x04 DOS FAT-16		*0x04 DOS FAT-16
			*0x07 NPFS/NTFS
	*0x0B Win95 FAT-32		*0x0B Win95 FAT-32
	*0x83 Linux		*0x83 Linux
Line 14:		Line 17:
	*0xB8 BSDI swap		*0xB8 BSDI swap
	*0xBF Solaris		*0xBF Solaris
			*0xFD Linux RAID

			In some Operating Systems (<i>e.g.</i> [[Linux]] and [[Windows]]) to put a filesystem directly on one of the slices. Conceptually, this looks like:

			[[image:Partition1.png]]

	~~In some Operating Systems this is enough ([[Linux]], [[Windows]]) to put a filesystem on using the entire slice.~~ Not so with most UNIX-like Operating systems which will put a partition table inside the slice. Individual partitions will hold filesystems such as / ([[root]]), /usr, /var, /tmp, /usr/home and so on. In [[OpenBSD]] up to 16 partitions are allowed. The program [[disklabel]] (in [[FreeBSD]] it's called bsdlabel) manages the partitions:		Not so with most other UNIX-like Operating systems (including all of the BSD variants and Solaris X86) which will put a partition table '''inside''' the slice. Individual partitions will hold filesystems such as / ([[root]]), /usr, /var, /tmp, /usr/home and so on. In [[OpenBSD]] up to 16 partitions are allowed. The program [[disklabel]] (in [[FreeBSD]] it's called bsdlabel) manages the partitions:

	# disklabel wd0		# disklabel wd0
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	i: 65802177 63 unknown # Cyl 0*- 65279		i: 65802177 63 unknown # Cyl 0*- 65279

	Note: ~~The 3rd partition or 'c' always represents the entire slice (In [[OpenBSD]]'s case the entire disk).~~ These partitions can then be [[newfs]]'ed and [[mount]]ed from the device which is represented by the name of the driver, the disk number (starting from 0) and the partition number (a through p).		Note: These partitions can then be [[newfs]]'ed and [[mount]]ed from the device which is represented by the name of the driver, the disk number (starting from 0) and the partition number (a through p). The 3rd partition or 'c' always represents the entire slice (In [[OpenBSD]]'s case the entire disk). Generally, slice 'c' should not be used directly for a filesystem. Visually, this looks similar to:

			[[image:Partition2.png]]

	$ df		$ df
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	...		...

	Solaris is even more different. Partitions are managed with the format command. Also the ~~devices~~ representing a [[filesystem]] look a ~~whole lot~~ different. ie. '''/dev/dsk/c0t0d0s2''' would indicate controller 0, target 0, drive 0 and slice 2. Don't get confused Solaris calls its partitions slices (yes different implementors different slinging of lingo). Notice that 2 represents the entire drive, just as 'c' in BSD does (3rd one from beginning).		Solaris is even more different. Partitions are managed with the [[format]] command. Also, the device files representing a [[filesystem]] look a much different: e.g. '''/dev/dsk/c0t0d0s2''' would indicate controller 0, target 0, drive 0 and slice 2. Don't get confused Solaris calls its partitions "slices" (yes different implementors different slinging of lingo). Notice that 2 represents the entire drive, just as 'c' in BSD does (3rd one from beginning).

Pbug at 11:10, 1 November 2005

2005-11-01T11:10:13Z

New page

To eliminate confusion here is a review of what a partition is. First you have a disk, this disk has a slice table (also called partition table for confusings sake). The slice table is modified/managed with the [[fdisk]] program. In the slice table you can have 4 primary slices or 3 primary slices and up to 23 logical slices. A slice is identified by an 8 bit number indicating what sort of slice this is here are a few common ones:

*0x04 DOS FAT-16
*0x0B Win95 FAT-32
*0x83 Linux
*0x82 Linux swap
*0x9F BSDI
*0xA5 FreeBSD
*0xA6 OpenBSD
*0xA8 Mac OS X
*0xA9 NetBSD
*0xAB Mac OS X Boot
*0xB7 BSDI files
*0xB8 BSDI swap
*0xBF Solaris

In some Operating Systems this is enough ([[Linux]], [[Windows]]) to put a filesystem on using the entire slice. Not so with most UNIX-like Operating systems which will put a partition table inside the slice. Individual partitions will hold filesystems such as / ([[root]]), /usr, /var, /tmp, /usr/home and so on. In [[OpenBSD]] up to 16 partitions are allowed. The program [[disklabel]] (in [[FreeBSD]] it's called bsdlabel) manages the partitions:

# disklabel wd0
# Inside MBR partition 3: type A6 start 65802240 size 246774465
# /dev/rwd0c:
type: ESDI
disk: ESDI/IDE disk
label: SAMSUNG SP1614C
flags:
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 16
sectors/cylinder: 1008
cylinders: 16383
total sectors: 312581808
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0 # microseconds
track-to-track seek: 0 # microseconds
drivedata: 0
16 partitions:
# size offset fstype [fsize bsize cpg]
a: 2097648 65802240 4.2BSD 2048 16384 328 # Cyl 65280 - 67360
b: 4194288 67899888 swap # Cyl 67361 - 71521
c: 312581808 0 unused 0 0 # Cyl 0 -310100
d: 12582864 72094176 4.2BSD 2048 16384 328 # Cyl 71522 - 84004
e: 227899665 84677040 4.2BSD 2048 16384 328 # Cyl 84005 -310095*
i: 65802177 63 unknown # Cyl 0*- 65279

Note: The 3rd partition or 'c' always represents the entire slice (In [[OpenBSD]]'s case the entire disk). These partitions can then be [[newfs]]'ed and [[mount]]ed from the device which is represented by the name of the driver, the disk number (starting from 0) and the partition number (a through p).

$ df
Filesystem 512-blocks Used Avail Capacity Mounted on
/dev/wd0a 2061100 144604 1813444 7% /
...

FreeBSD is different (and more obvious) it is made up of the driver name, the disk number (starting from 0), an s to indicate slice, the slice number (starting at 1) and the partition number (a through h, yes only 8 partitions):

$ df
Filesystem 1K-blocks Used Avail Capacity Mounted on
/dev/idad0s1a 495726 61046 395022 13% /
...

Solaris is even more different. Partitions are managed with the format command. Also the devices representing a [[filesystem]] look a whole lot different. ie. '''/dev/dsk/c0t0d0s2''' would indicate controller 0, target 0, drive 0 and slice 2. Don't get confused Solaris calls its partitions slices (yes different implementors different slinging of lingo). Notice that 2 represents the entire drive, just as 'c' in BSD does (3rd one from beginning).