partmap 15 limit Revisited

[Daniel Gimpelevich]

mascarasnake <dontdrill <at> earthlink.net> writes:

> 
> Before my question, just a note to Dr. Clint. One of the reasons *nix is 
> so great; I type this email from my 586 (FC1) ssh -X'd into my 7500 
> while I try to rearrange my drives on my G3. Maybe a little too geeky, 
> but, damn that's cool.
> 
> Now my question -
> 
> Has anyone else had this funky partmap thing come up? I'm unable to 
> combine the partitions using pdisk on the mac side, using Disk Druid, or 
> using anaconda's pdisk.
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> 
> 

If you look at the major and minor device numbers in the /dev/hdXX and /dev/sdXX
entries you will see that /dev/hdXX entries advance to the next disk every 64
minor device numbers, but /dev/sdXX entries advance to the next disk every 16
minor device numbers! That means that while the Linux kernel could theoretically
address 63 partitions on IDE devices, only 15 are possible on SCSI or
SCSI-emulated devices. This flaw is built into the Linux kernel by design, and
I'm not sure why. This limitation is present on ALL Linux computers, regardless
of platform or partitioning scheme. I believe it's very likely that this will
NEVER be fixed.

It is possible to use the pdisk on the YDL 3.0.1 (not 3.0) rescue disk to
combine adjacent free partitions. Use the 't' command on the second free
partition in a row and change the type to 'crap' or some such thing. Then delete
that partition. Voila! One Apple_Free partition!