[Qemu-devel] Magic Numbers for Qemu Images

[Friedrich Schwittay]

/* CC´d to address@hidden:
  Just to have it available to Qemu-Devs
  who will acually have real use for it */

Hi Christos,

i recently added some lines to my magic
file and since there might be a hole bunch
of  people out there pointing file(1) on
qemu images it would be nice, if you include
them into available file(1) releases.

I would appreciate if you keep my name in there, thx.

######## And here they are:############
#--------------------------------------------------------------------
# Qemu Emulator Images
# Lines written by Friedrich Schwittay (address@hidden)
# Made by reading sources and doing trial and error on existing
# qcow files
0       string  QFI     Qemu Image, Format: Qcow

# Uncomment the following line to display Magic (only used for debugging
# this magic number)
#>0     string  x       , Magic: %s

# There are currently 2 Versions: "1" and "2"
# I do not use Version 2 and therefor branch here
# but can assure: it works (tested on both versions)
# Also my Qemu 0.9.0 which uses this Version 2 refuses
# to start in its bios
>0x04   belong  2       , Version: 2
>0x04   belong  1       , Version: 1

# Using the existence of the Backing File Offset to Branch or not
# to read Backing File Information
>>0xc    belong  >0      , Backing File( Offset: %d
>>>(0xc.L)       string  >\0     , Path: %s

# Didnt got the Trick here how qemu stores the "Size" at this Position
# There is actually something stored but nothing makes sense
# The header in the sources talks about it
#>>>16   lelong  x       , Size: %d

# Modification time of the Backing File
# Really usefull if you want to know if your backing
# file is still usable together with this image
>>>20    bedate  x       , Mtime: %s )

# Dont know how to calculate in Magicfiles
# Also: this Information is not reliably
#       stored in image-files
>>24     lelong  x       , Disk Size could be: %d * 256 bytes
####### End of Qemu-Lines #############

I will make some more if there is Interest in it
For me it just makes it possible to check where i
have to put the corresponding Backing File when the
location has changed because tool "qemu-img info"
refuses to show this information if the backing
file is not in the right position.

Best Wishes
Friedrich Schwittay

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