On 03/18/2011 01:36 PM, JB wrote: > Mikkel <mikkel <at> infinity-ltd.com> writes: > >> ... >> What kind of problems would it cause? >> >>> OSs, e.g. >>> # fdisk -l /dev/sda >>> ... >>> /dev/sda1 63 81920159 40960048+ 7 HPFS/NTFS >>> /dev/sda2 * 81920160 111222719 14651280 a5 FreeBSD >>> ... >>> /dev/sda9 216715023 246017519 14651248+ 83 Linux >>> >>> # dmesg | grep bsd >>> [ 1.550749] sda2: <bsd: sda10 sda11 sda12 sda13 sda14 > >>> ... > > I would refer you to this thread once more where I described and tested them. > > But I will do it one more time: > > 1. Linux has two widely used partition table display/manipulation entries: > fdisk > cfdisk > and there are more of them. > If none of them show all partitions (inclusive *BSD slices) as in > an example above, then these entries are fooling users and sysadmins. > This is lunacy and can be costly. Believe it or not but users rely on > truthfullness and clarity (nothing shall be hidden) when it comes to > the one and only one source of a particular info, based on which they make > decisions. This is a problem with the specific tools. They do not stop you when you try and mix a DOS partition table and a BSD disklabel on the same drive. The problem is that BSD is letting you mix the partition tables on the same drive. You have to remember that fdisk and cfdisk are old tools that were written in the days when an admin was supposed to know what he was doing, and the tools will allow him to shoot himself in the foot if that is what he wants. The newer tools like parted make this harder, but you can still do it. You might want to read the man pages on the limitations of fdisk and cfdisk. > What if they decide they need an additional partition and look at fdisk > for the next available (they do not see hidden *BSD slices) ? > Is that not dangerous ? Sure. That is a problem with using the old tools. You are not supposed to mix DOS and BSD type partition table on the same drive, but if that is what you want to do, they will let you. You will also run into the same problem if you have Windows on the drive, and add a logical drive. Linux handles this, as they use the same method when dealing with a DOS partition table. > 2. I have shown that *BSD slice /dev/<name> can be temporarily mounted (and > serve as a source of data) and at the same time the same /dev/<name> can > be used to create a new Linux partition. > Is that not dangerous ? Definitly - you should not try and mix a DOS partition table with a BSD disk label partition table. They are not compatible. Do not try to use tools that do exactly what you tell them to do, and let you decide if that is the correct thing to do if you do not want to run into the problem. > 3. I have shown that *BSD slice /dev/<name> can be permanently mounted thru > /etc/fstab (and serve as a source of data) and at the same time the same > /dev/<name> can be used to create a new Linux partition. > After that, due to mismatch of superblock/bad magic number that *BSD mount > will be refused. > Is that not dangerous ? > If that /dev/<name> were used to create a new stand-alone UFS partition > (or anything for that matter that would match UFS superblock/bad magic > number), perhaps the fstab-base auto mount would be successful, serving who > knows what data. > Is that not dangerous ? > Yes, it is. Linux should refuse to mount a drive with a mix of DOS type and BSD type partitions on the same drive, or at least mount it read/only. Then again, BSD should refuse to create partitions on a drive that already has a DOS type partition table. While you are checking things out, see how Linux handles a drive with a proper BSD partition table (drivelabel). I suspect that fdisk will report things properly, and it will get mounted correctly under Linux. My take on this is that fdisk on *BSD does not stop you from shooting yourself in the foot by creating a partition table like this, and fdisk under Linux does not stop you from shooting yourself in the foot again. This is why you need root access to do these things - you are supposed to know what you are doing, and not do things like this. But if you have a reason for doing them, the system will let you. Did you know that you can use the entire drive, without a partition table, as a file system? If you want to run "mke2fs /dev/sda" as root, it will let you. If you want to run "tar -cf /dev/sdb /home" as root, and you have a sdb, it will use the entire drive as a tar archive. And it will do it even if you have a partition table, and mounted file systems on it. (It will not do it if you have /dev/sdb mounted, but it will if you have /dev/sdb1 mounted.) I have not tried it, but I suspect you can do the same thing under *BSD. It should work on ANY UNIX-type system as long as you are the super-user, what ever they call him. Mikkel -- Do not meddle in the affairs of dragons, for thou art crunchy and taste good with Ketchup!
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