Hi Clive, > > > Is there a restriction on the number of partitions you can have > > > within an 'extended' partition? > > > > > > He is getting an error report when trying to make the '/Home' > > > partition, along the lines of 'cannot make 17th partition'. > > > Installation has produced the '/' and swap partitions but fails on > > > /Home. (Linux is on the second disk) > > > > Under the standard (MBR) scheme, you can have up to four *primary* > > partitions. One of these can be an *extended* partition, which can > > then contain other *logical* partitions. > > > > The limit to the number of logical partions is OS dependant. For > > IDE/SATA disks on Linux I'm pretty sure it's 64.
I think John's right. Three usable primaries, the fourth primary is the extended one so isn't used directly but can contain up to 60 logical partitions. So the kernel tracks 64 partitions, 63 of which can contain filesystems. > Thanks for that info: do you know if it's less for Win XP? He's used > Partition Magic to partition the drives. It doesn't matter what he used originally to partition the drive since the definitions of the logical partitions in the extended one are "chained" together. At the start of the extended is a definition of the first logical partition and the address of the next definition, or 0 if this is the last definition. So the extended partition can have as many logical partitions as you've disk space for; it doesn't mean every OS will be able to access them, e.g. there's only 26 drive letters, A-Z, on some Microsoft OSes. http://en.wikipedia.org/wiki/Extended_partition has some diagrams. Your friend is getting the error from the Linux installation program when it's trying to create the /home partition having already created / and swap. I've found https://help.ubuntu.com/10.10/installation-guide/i386/partition-programs.html which says Linux limits the partitions per drive to 15 partitions for SCSI disks (3 usable primary partitions, 12 logical partitions), and 63 partitions on an IDE drive (3 usable primary partitions, 60 logical partitions). However the normal Ubuntu system provides only 20 devices for partitions, so you may not install on partitions higher than 20 unless you first manually create devices for those partitions. An older version of the same page, https://help.ubuntu.com/7.04/installation-guide/i386/partition-programs.html, gives the commands needed to create those extra devices but it sounds a bit odd to me. I'd have thought with the udev filesystem giving us a dynamic /dev these days that we'd no longer need to use mknod for this? The installer would alter the disk and get the kernel to re-read the partition table or just that one created partition and udev would create the device? So perhaps the 10.10 installation manual is out of date? If someone can run a VM on a "disk" with lots of logical partitions perhaps they can test it. It would match your friend's error about the 17th partition. Four primaries plus 16 logicals would take up the 20, foiling the 17th logical. Cheers, Ralph. -- Next meeting: Bournemouth, Tuesday 2011-02-01 20:00 Meets, Mailing list, IRC, LinkedIn, ... http://dorset.lug.org.uk/ How to Report Bugs Effectively: http://goo.gl/4Xue
