linux-imx

It implements all of

  - Xenix FS,

  - SystemV/386 FS,

  - Coherent FS.

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To install:

* Answer the 'System V and Coherent filesystem support' question with 'y'

  when configuring the kernel.

* To mount a disk or a partition, use

    mount [-r] -t sysv device mountpoint

  The file system type names

               -t sysv

               -t xenix

               -t coherent

  may be used interchangeably, but the last two will eventually disappear.

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Bugs in the present implementation:

- Coherent FS:

  - The "free list interleave" n:m is currently ignored.

  - Only file systems with no filesystem name and no pack name are recognized.

  (See Coherent "man mkfs" for a description of these features.)

- SystemV Release 2 FS:

  The superblock is only searched in the blocks 9, 15, 18, which

  corresponds to the beginning of track 1 on floppy disks. No support

  for this FS on hard disk yet.

​

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These filesystems are rather similar. Here is a comparison with Minix FS:

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* Linux fdisk reports on partitions

  - Minix FS     0x81 Linux/Minix

  - Xenix FS     ??

  - SystemV FS   ??

  - Coherent FS  0x08 AIX bootable

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* Size of a block or zone (data allocation unit on disk)

  - Minix FS     1024

  - Xenix FS     1024 (also 512 ??)

  - SystemV FS   1024 (also 512 and 2048)

  - Coherent FS   512

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* General layout: all have one boot block, one super block and

  separate areas for inodes and for directories/data.

  On SystemV Release 2 FS (e.g. Microport) the first track is reserved and

  all the block numbers (including the super block) are offset by one track.

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* Byte ordering of "short" (16 bit entities) on disk:

  - Minix FS     little endian  0 1

  - Xenix FS     little endian  0 1

  - SystemV FS   little endian  0 1

  - Coherent FS  little endian  0 1

  Of course, this affects only the file system, not the data of files on it!

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* Byte ordering of "long" (32 bit entities) on disk:

  - Minix FS     little endian  0 1 2 3

  - Xenix FS     little endian  0 1 2 3

  - SystemV FS   little endian  0 1 2 3

  - Coherent FS  PDP-11         2 3 0 1

  Of course, this affects only the file system, not the data of files on it!

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* Inode on disk: "short", 0 means non-existent, the root dir ino is:

  - Minix FS                            1

  - Xenix FS, SystemV FS, Coherent FS   2