On 2015-10-06 19:25, Mikael wrote: > So then I'll just learn that sector 80 and up are "safe" for "user data", > and it's up to all users to take care that any non-UFS/swap/RAID partitions > never go below 80.
I don't think you can expect swap partitions to honour those first sectors... generally, it i expected that the first partition (by convention 'a' but as you found out yourself not by enforcement) should contain either an ffs(/ffs2) file system or a RAID partition (which in turn contains a label and partitions of its own). Why would you need to reserve space manually? Are you expecting to run something that stores data on raw partitions? I thought that practice more or less died out in the nineties... That said, there are certainly use cases to point BSD partitions in non-standard places, for example if you want to be able to access file systems from another MBR partition that belongs to another bootable system. But that doesn't interfere with the BSD usable area, let alone its precious first sectors. > But how does the behavior of the first added partition by default > overlapping the disklabel "save butts" - > Does this behavior fill any practical function today, and also when the > user (me) makes there be no overlap, could/do I break anything? If you place a 4.2BSD or a RAID partition from the first sector (64) of the BSD usable part of the disk (as limited by the "boundstart" and "boundend" disklabel parameters) you will never get in trouble. Anything else and you need to know more about the system internals to be safe. You ask about saved butts. Just a couple of example scenarios: Consider the option to encasing the partition metadata in the first partition (and again, first physical address-wise, not first partition letter-wise), which is to leave a gap in the beginning: First of all, I'm not even sure the boot code is able to cope with that scenario, but let's say it is. Whenever you want to add a new partition, disklabel will suggest you populate the first free area on your disk - guess where that is going to be... If you wreck your disklabel and have done something non-standard, such as move the first partition from its expected position, you're pretty much in the dark when it comes to actually *find*, not to mention hopefully recover, your partitions. It is well known and understood since decades what's on these first sectors of a) a disk, b) of the BSD usable area and c) of each partition (type). Why are you having trouble accepting that things are the way they are and that they WORK as they are, if you don't turn everything on its head? Well, at least they work until you start messing with things you have not yet had any experience with. The upside is you'll quickly gain useful experience, of how not to do. :-) Regards, /Benny
