Main Area and Open Discussion > Living Room
Multibooting and Partitioning Experiments
wolf.b:
I don't own the PC standard but just use it like everybody else.
--- End quote ---
Yeah, right. Reading your publications I would say: you use it like nobody else. :up:
But seriously, I am full of admiration for your work. "Der Bootmeister" for president.
Still seriously, if there is such a thing as "the PC standard", where can I read it? I always assumed that the way how CHS values and LBA values are written to the partition table entries are more like a loose convention. I have noticed on many occasions that the partition table (inside the master boot record (MBR)) and more often the extended partition tables (inside the extended partition boot record (EPBR)) written by Ranish Partition Manager (RPM) were declared as errors (partition table error 116, if I remember correctly) by PowerQuest Partition Magic, and PQmagic offered very kindly to correct those errors. Neither with nor without consequent PQmagic correction, have I ever experienced a problem with getting any MS OS to run from logical drive that has an incorrect CHS address in EPBR. Any thoughts on that? My thoughts are these:
* All tested MS OS don't seem to care about CHS address, but use LBA address instead. Not to care here is meant to say: maybe the OS loader does read CHS address values, but it does not put out a message about them being off the mark.
* As long as the crucial values are correct, the rest can be ignored or (ab)used otherwise, with no negative consequences. If I regard the boot sequence as a means to the end of having a OS at my command (GUI or CLI), the only negative consequence would be to not have that OS to boss around. Mind you, getting error messages from particular tools that don't like the way other tools or I manage the hard disk is nothing I would call positive consequence, it is merely a nuisance.
If there is a way to get more partitions out in the normal way then I would love to know.
--- End quote ---
Sorry for this stupid question: is your understanding of "normal way" the same as: only grub build in commands allowed?
Without that limitation I can think of at least one way to get more than 44 logical partitions. I don't want to bore you or the rest of the forum readers (in case there are any left) with lengthy details.
Just for the record: Ranish Partition Manager (shareware) supports a maximum of 32 primary partitions. Trombettworks' system supports as many primary partitions, until I run out of ink or paper (or disk space more likely). I have written for myself a batch that takes over the role of the ink and paper. Currently I juggle with about 50 primary partitions, but I guess the limit is way beyond 256 partitions.
LVM is not universally supported ...
--- End quote ---
What is LVM, please? Linux Virtual Machine :-* , no, but maybe Linux Volume Manager.
Actually a search came up with What is LVM? Answer: LVM is a Logical Volume Manager for the Linux operating system.
Greetings
Wolf
saikee:
The PC standard as it exists today is just an overserved standard. By that I mean every mobo you purchase has a Bios that will read off the first sector of the first hard disk it is asked to boot. The Bios goes into the 446th to 51oth byte position to read off the 4 primaries. Thereafter is up to the OS how to make use of the information. This observed standard means if an OS like a Solaris or Linux can boot off a PC without inflicting damage to other OS in the same hard disk.
If a partition happens to be fat32 which is supported by virtually all OSes then every OS can read/write its content.
If someone comes along to make a MBR bigger than 512 byes then other OSes cannot co-exist with it and many just die eventually due to a lack of popularity.
The LBA is only way to address a big hard disk nowaday. fat16 filing system has a maximum address of 2Gb and putting it beyond the first 4Gb area in the hard disk means no OS can access it.
Traditionally a MS system can only operate from a logical partition if a MS boot loader is available in a primary partition to boot it, unless the system is hacked so that it can boot directly from a logical partition as a stand alone system.
On the maximum number of partitions I have stayed away from the proprietary software because my interest is to have the systems that can co-exist with each other. I am aware 256 primaries is no object by putting in a hard disk management layer. One can use virtual machine too. LVM is anther way but they all suffer limitation of needing a driver which cannot be put into every operating system or boot loader. What is good about LVM if a PC user cannot install a Vista inside it? What is good about installing a Linux as a virtual machine inside a Windows host if that Linux cannot communicate with other Linux partition and read/write information?
LVM is used by Linux but not universally supported. Some families of Linux use it and so the kernel and ram disk files are pre-packaged with its driver so that the distros can be installed inside a LVM. Others recognise it only after the distro has been loaded but not before. This make it impossible to install these distros into a LVM. There are Linux that pride themself as small as possible and all unnecessary drivers are thrown away.
To me a large number of partitions are only useful if a pC user can install operating systems inside, otherwise they may just as well as subdirectories, as Linux and new MS Windows can play tunes with their ownerships.
wolf.b:
Hi saikee,
I don't know how to put this, so it is probably best to apologize beforehand in case I annoy you: Sorry for my bad attitude, no offense intended. :-[ I just try to get things straight in my mind. And also I like to discuss rather than argue.
... a Bios that will read off the first sector of the first hard disk it is asked to boot. The Bios goes into the 446th to 51oth byte position to read off the 4 primaries.
--- End quote ---
I think, the BIOS will read the first sector of the hard disk, if it is asked to boot from it. Agreed. It seems to be ?standard? behavior to put it into RAM at location 0000:7C00. But the BIOS does not show any interest in the partition table (447th to 510th byte of the MBR). It is the Initial Program Loader (IPL = the first 446 bytes of the MBR) that copies the entire MBR (512 bytes =446 bytes IPL + 4*16 bytes partition table + 2 bytes signature) to a ?standard? location in memory (from 0000:7C00 to 0000:0600).
* The Master Boot Record (MBR) and What it Does
* HIW: Master Boot Record
* Windows 95b MBR
* Windows 2000 MBR
If a partition happens to be fat32 which is supported by virtually all OSes then every OS can read/write its content.
--- End quote ---
Maybe I have a lot of old hardware with old OS, but I think FAT16 is supported by a lot more OS's than FAT32. Not even Windows 95 or Windows NT 4.0 supported FAT32, not to mention MS DOS previous to version 7.1.
fat16 filing system has a maximum address of 4Gb and putting it beyond the first 4Gb area in the hard disk means no OS can access it.
--- End quote ---
I would like to repeat my statement of reply#6 of this thread:
I have tested my Windows 98 SE again, just to be sure. It is installed on a logical drive. That logical drive is located 12 GB past the start of the drive.
--- ---First physical sector = 25,430,958 (Cyl 1,583, Hd 1 , Sect 1)
Last physical sector = 29,623,859 (Cyl 1,843, Hd 254, Sect 63)
It boots OK.
--- End quote ---
And I want to add that it is a FAT16 formatted partition. It starts 12 GB past the start of the disk and ends 14 GB past the start of the disk. In case of interest, I can try to copy it to the very end of the hard disk (size is 250 GB or 240 GiB) and see if it is bootable. Actually I am interested myself now, so I will check it out and post the result.
I am aware 256 primaries is no object by putting in a hard disk management layer.
--- End quote ---
Would you mind very much if I took that technical phrase "hard disk management layer" and use it to describe my batch files? It makes it sound as if I knew what I am talking about.
What is good about installing a Linux as a virtual machine inside a Windows host if that Linux cannot communicate with other Linux partition and read/write information?
--- End quote ---
I have VMware running on Windows XP. In there I can boot Linux from a CDROM (have not yet installed it to a virtual disk) and I get read/write access to my Ubuntu partition which is installed on a logical drive of my physical hard disk. After finishing this post, I reboot into that Ubuntu installation and post what damage I have done. (I have created an empty file: "/WolfWasHere"). Have I misunderstood that question?
I hope that I don't come across as a smartassed Know-it-all, because I feel that I know much too little about multibooting to be able to give advice or even write tutorials like you have done. I appreciate the way you are sharing your knowledge and I am honored that you read this thread and answer my questions. :)
Greetings
Wolf
wolf.b:
Quick note from inside Ubuntu: the file "/WolfWasHere" exists and its creation does not seem to have caused much damage to the filesystem.
wolf.b:
Another quick note: Windows 98 SE works when installed in the last 2 GB of a 250 GB HDD. :)
That is a logical drive with FAT16 filesystem.
But it only runs in 16 bit save mode secondary to my motherboard not being old enough. :(
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