[pkg-fso-maint] debian install.sh giving wrong partitioning sizes

[Steffen Möller]

Dear Sam,

On 09/10/2011 12:09 AM, Sam Tygier wrote:
> I am having trouble at the partitioning stage of install.sh, the partitions are not created the size I ask for.  I have tried
> variouscombinations of the env vars, and command line args.
> 
> # TASKS="ALL" QI=true ./install.sh --part1-size 4000 --swap-size 256  partition
> gives:
> 
> Disk /dev/mmcblk0: 8166 MB, 8166309888 bytes
> 4 heads, 16 sectors/track, 249216 cylinders, total 15949824 sectors
> Units = sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disk identifier: 0x2940d389
>         Device Boot      Start         End      Blocks   Id  System
> /dev/mmcblk0p1            2048      241404      119678+  83  Linux
> /dev/mmcblk0p2          241405    15949823     7854209+  82  Linux swap / Solaris
> 
> a ~100 MB /dev/mmcblk0p1 and 7GB /dev/mmcblk0p2 for swap.
> 
> install.sh calculates the size of the first partition in cyclinders, by subtracting the size of swap. It then uses the sizes in
> cylinders to create the partitions.
> 
> SHR has fdisk (util-linux-ng 2.18), which defaults to working in sectors. so fdisk asks for sectors, and install.sh replies in
> cylinders.
> 
> the quick fix on SHR seems to be to call fdisk with "fdisk /dev/mmcblk0 -u=cylinders", but this will probably give an error if you
> do it on other fdisks. I could make a patch to to try to detect which fdisk is being used, and conditionally add the flag.
> 
> it looks like in the future fdisk will use sectors, so the real solution is probably do the calculations in sectors. The "-u"
> should make sure any fdisk version uses sectors.

I recall many contributions from many sides to that part of install.sh. A varying behaviour of fdisk indeed explains a lot to me.
This is why my desktop's fdisk (GNU Fdisk 1.2.4) gives me:

	-u, --sector-units
              use sectors, instead of cylinders for a default unit.
	-C, --cylinders=CYLINDERS
              Specify the number of cylinders of the disk. Currently does nothing, it is left for Linux fdisk compatibility.

So this is somewhat different, -u does not need any extra options, -C means something different. This sniplet works for me

	b=`/sbin/fdisk --version`
	fdiskFlags=""
	if echo $b|grep -q ^GNU; then
	        echo "I am a GNU: $b"
	        #fdiskFlags="-u" # sectors
	        fdiskFlags=""    # cylinders
	else
	        echo "Who am I, util-linux-ng maybe?"
	        fdiskFlags=""             # sectors
	        fdiskFlags="-u=cylinders" # cylinders
	fi
	
	echo "The flags to use are: $fdiskFlags"


I think we should prefer an explicit failure over an unsupported fdisk option over presuming any default unit. If it is not too
cumbersome, could you please prepare a patch that works for you and introduces the explicit unit setting through some extra magic
like outlined above? This would be great.

Many thanks and regards,

Steffen