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RFC: "file" magic for ext4

DISCUSSION Eric Sandeen 2 participants 2 messages Jan 30, 2008 – Jan 31, 2008

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Eric Sandeen

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#0 lore raw

This seems to work fine; any comments, either about the logic, or the text descriptions, or the various options I've shown/not shown?

To test, copy your "magic" file somewhere local, replace the ext2/3 section with the following, and do something like:

# file -C -m magic; file -m ./magic -s /dev/sda1

-Eric

# ext2/ext3 filesystems - Andreas Dilger <[email protected]>
0x438   leshort         0xEF53          Linux
Quoted 2 lines
0x44c  lelong          x               rev %d
0x43e  leshort         x               \b.%d

# No journal? ext2

Quoted 2 lines
0x45c  lelong          ^0x0000004      ext2 filesystem data
>0x43a leshort         ^0x0000001      (mounted or unclean)

# Has a journal? ext3 or ext4

Quoted 1 line

0x45c lelong &0x0000004

# and small INCOMPAT?

Quoted 1 line
Quoted 1 line

0x460 lelong <0x0000040

# and small RO_COMPAT?

Quoted 1 line
Quoted 1 line
Quoted 1 line

0x464 lelong <0x0000008 ext3 filesystem data

# else large RO_COMPAT?

Quoted 1 line
Quoted 1 line
Quoted 1 line

0x464 lelong >0x0000007 ext4 filesystem data

# else large INCOMPAT?

Quoted 1 line
Quoted 1 line

0x460 lelong >0x000003f ext4 filesystem data

# General flags for any ext* fs

Quoted 2 lines
0x460  lelong          &0x0000004      (needs journal recovery)
0x43a  leshort         &0x0000002      (errors)

# INCOMPAT flags

Quoted 1 line

0x460 lelong &0x0000001 (compressed)

#>0x460 lelong          &0x0000002      (filetype)
#>0x460 lelong          &0x0000010      (meta bg)
>0x460  lelong          &0x0000040      (extents)
>0x460  lelong          &0x0000080      (64bit)
#>0x460 lelong          &0x0000100      (mmp)
#>0x460 lelong          &0x0000200      (flex bg)
# RO_INCOMPAT flags
#>0x464 lelong          &0x0000001      (sparse super)
>0x464  lelong          &0x0000002      (large files)
>0x464  lelong          &0x0000008      (huge files)
#>0x464 lelong          &0x0000010      (gdt checksum)
#>0x464 lelong          &0x0000020      (many subdirs)
#>0x463 lelong          &0x0000040      (extra isize)
#1 lore raw
Quoted 8 lines · Eric Sandeen

This seems to work fine; any comments, either about the logic, or the text descriptions, or the various options I've shown/not shown?

To test, copy your "magic" file somewhere local, replace the ext2/3 section with the following, and do something like:

Quoted 5 lines
# file -C -m magic; file -m ./magic -s /dev/sda1

-Eric

# ext2/ext3 filesystems - Andreas Dilger <[email protected]>

Lol, you may as well fix up the email.... [email protected] will probably be the least transient.

Quoted 21 lines
0x438   leshort         0xEF53          Linux
>0x44c  lelong          x               rev %d
>0x43e  leshort         x               \b.%d

# No journal? ext2

Quoted 2 lines
0x45c  lelong          ^0x0000004      ext2 filesystem data
>0x43a leshort         ^0x0000001      (mounted or unclean)

# Has a journal? ext3 or ext4

Quoted 1 line

0x45c lelong &0x0000004

# and small INCOMPAT?

Quoted 1 line
Quoted 1 line

0x460 lelong <0x0000040

# and small RO_COMPAT?

Quoted 1 line
Quoted 1 line
Quoted 1 line

0x464 lelong <0x0000008 ext3 filesystem data

# else large RO_COMPAT?

Quoted 1 line
Quoted 1 line
Quoted 1 line

0x464 lelong >0x0000007 ext4 filesystem data

# else large INCOMPAT?

Quoted 1 line
Quoted 1 line

0x460 lelong >0x000003f ext4 filesystem data

# General flags for any ext* fs

Quoted 2 lines
0x460  lelong          &0x0000004      (needs journal recovery)
0x43a  leshort         &0x0000002      (errors)

# INCOMPAT flags

Quoted 1 line

0x460 lelong &0x0000001 (compressed)

Quoted 13 lines
#>0x460 lelong          &0x0000002      (filetype)
#>0x460 lelong          &0x0000010      (meta bg)
>0x460  lelong          &0x0000040      (extents)
>0x460  lelong          &0x0000080      (64bit)
#>0x460 lelong          &0x0000100      (mmp)
#>0x460 lelong          &0x0000200      (flex bg)
# RO_INCOMPAT flags
#>0x464 lelong          &0x0000001      (sparse super)
>0x464  lelong          &0x0000002      (large files)
>0x464  lelong          &0x0000008      (huge files)
#>0x464 lelong          &0x0000010      (gdt checksum)
#>0x464 lelong          &0x0000020      (many subdirs)
#>0x463 lelong          &0x0000040      (extra isize)

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.