On 04.01.2011 16:02, Richard Troth wrote:
Mark is correct: one automagically created partition. Worse, there is no 'fdasd' or 'fdisk' management of that partition.
Actually you *can* use fdisk to manage partitions on DASDs which are formatted with a fixed block size (ECKD LDL or FBA), regardless of whether DIAG access is used or not. Example: to get rid of the implicitly created DASD partitions on /dev/dasdx, use these commands: echo w | fdisk /dev/dasdx This will write an MS-DOS type master boot record with an empty partition table to dasdx. Note that some operations (mkfs.ext, pvcreate) seem to overwrite the MBR so the fdisk step should be performed last. More background: When a DASD is set online, the Linux kernel attempts to recognize the partition type by letting all supported partition type handlers have a look at the disk contents. This process happens sequentially and stops once a handler indicates that it has found a valid partition. The DASD partition handler comes very late in the list, so pretty much any partitioning scheme supported by the Linux kernel can be used to circumvent implicit DASD partitioning.
WORSE STILL, you *must* put the filesystem into the "partition" (such as it is) if you are going to boot from this disk. A filesystem in /dev/dasdx will be clobbered by the first stage of the boot loader, while a filesystem in /dev/dasdx1 is protected by the extra 8K of padding. (12K total) I checked it again this morning. The bootstrap overwrites the root inode.
This is a side effect of the zipl boot loader design, more precisely of the size of the first stage IPL code that is written to block 0. It's conceivable that this could be changed in the future.
God bless whoever in Boeblingen fixed this problem for FBA disks. You can use the pseudo-partition, or not. You can boot from them either way.
This "problem" never existed for FBA disks - the first stage FBA IPL code only spans a single FBA block. According to Martin Schwidefsky this approach was chosen because there were no format or layout restrictions for FBA disk so they decided to keep it similar to the Intel world. Regards, Peter Oberparleiter ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
